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class="vector-toc-numb">2</span> <span>Definition</span> </div> </a> <button aria-controls="toc-Definition-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Definition subsection</span> </button> <ul id="toc-Definition-sublist" class="vector-toc-list"> <li id="toc-Variants" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Variants"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Variants</span> </div> </a> <ul id="toc-Variants-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Implementation_issues" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Implementation_issues"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Implementation issues</span> </div> </a> <ul id="toc-Implementation_issues-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Sample_C_code" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Sample_C_code"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Sample C code</span> </div> </a> <ul id="toc-Sample_C_code-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Examples" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Examples"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Examples</span> </div> </a> <button aria-controls="toc-Examples-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Examples subsection</span> </button> <ul id="toc-Examples-sublist" class="vector-toc-list"> <li id="toc-Binary_delta_compression" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Binary_delta_compression"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Binary delta compression</span> </div> </a> <ul id="toc-Binary_delta_compression-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Delta_encoding_in_HTTP" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Delta_encoding_in_HTTP"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2</span> <span>Delta encoding in HTTP</span> </div> </a> <ul id="toc-Delta_encoding_in_HTTP-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Delta_copying" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Delta_copying"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.3</span> <span>Delta copying</span> </div> </a> <ul id="toc-Delta_copying-sublist" class="vector-toc-list"> <li id="toc-Online_backup" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Online_backup"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.3.1</span> <span>Online backup</span> </div> </a> <ul id="toc-Online_backup-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Delta_updates" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Delta_updates"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.3.2</span> <span>Delta updates</span> </div> </a> <ul id="toc-Delta_updates-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Diff" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Diff"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.4</span> <span>Diff</span> </div> </a> <ul id="toc-Diff-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Git" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Git"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.5</span> <span>Git</span> </div> </a> <ul id="toc-Git-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-VCDIFF" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#VCDIFF"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.6</span> <span>VCDIFF</span> </div> </a> <ul id="toc-VCDIFF-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-GDIFF" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#GDIFF"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.7</span> <span>GDIFF</span> </div> </a> <ul id="toc-GDIFF-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-bsdiff" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#bsdiff"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.8</span> <span>bsdiff</span> </div> </a> <ul id="toc-bsdiff-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> 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class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Delta-Kodierung" title="Delta-Kodierung – German" lang="de" hreflang="de" data-title="Delta-Kodierung" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Delta_encoding" title="Delta encoding – Spanish" lang="es" hreflang="es" data-title="Delta encoding" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Codage_diff%C3%A9rentiel" title="Codage différentiel – French" lang="fr" hreflang="fr" data-title="Codage différentiel" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EB%8D%B8%ED%83%80_%EB%B6%80%ED%98%B8%ED%99%94" title="델타 부호화 – Korean" lang="ko" hreflang="ko" data-title="델타 부호화" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Codifica_delta" title="Codifica delta – Italian" lang="it" hreflang="it" data-title="Codifica delta" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E5%B7%AE%E5%88%86%E7%AC%A6%E5%8F%B7%E5%8C%96" title="差分符号化 – Japanese" lang="ja" hreflang="ja" data-title="差分符号化" data-language-autonym="日本語" 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id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Type of data transmission method</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Not to be confused with <a href="/wiki/Elias_delta_coding" title="Elias delta coding">Elias delta coding</a> or <a href="/wiki/Delta_modulation" title="Delta modulation">delta modulation</a>.</div> <p><b>Delta encoding</b> is a way of storing or transmitting <a href="/wiki/Data" title="Data">data</a> in the form of <i><a href="/wiki/Data_differencing" title="Data differencing">differences</a></i> (deltas) between sequential data rather than complete files; more generally this is known as <a href="/wiki/Data_differencing" title="Data differencing">data differencing</a>. Delta encoding is sometimes called <b>delta compression</b>, particularly where archival histories of changes are required (e.g., in <a href="/wiki/Revision_control_software" class="mw-redirect" title="Revision control software">revision control software</a>). </p><p>The differences are recorded in discrete files called "deltas" or "diffs". In situations where differences are small – for example, the change of a few words in a large document or the change of a few records in a large table – delta encoding greatly reduces data redundancy. Collections of unique deltas are substantially more space-efficient than their non-encoded equivalents. </p><p>From a logical point of view, the difference between two data values is the information required to obtain one value from the other – see <a href="/wiki/Relative_entropy" class="mw-redirect" title="Relative entropy">relative entropy</a>. The difference between identical values (under some <a href="/wiki/Equivalence_relation" title="Equivalence relation">equivalence</a>) is often called <i>0</i> or the neutral element. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Simple_example">Simple example</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=1" title="Edit section: Simple example"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Perhaps the simplest example is storing values of bytes as differences (deltas) between sequential values, rather than the values themselves. So, instead of 2, 4, 6, 9, 7, we would store 2, 2, 2, 3, −2. This reduces the <a href="/wiki/Variance" title="Variance">variance</a> (range) of the values when neighbor samples are correlated, enabling a lower bit usage for the same data. <a href="/wiki/Interchange_File_Format" title="Interchange File Format">IFF</a> <a href="/wiki/8SVX" title="8SVX">8SVX</a> sound format applies this encoding to raw sound data before applying compression to it. Not even all 8-bit sound <a href="/wiki/Sampling_(signal_processing)" title="Sampling (signal processing)">samples</a> compress better when delta encoded, and the usability of delta encoding is even smaller for 16-bit and better samples. Therefore, compression algorithms often choose to delta encode only when the compression is better than without. However, in <a href="/wiki/Video_compression" class="mw-redirect" title="Video compression">video compression</a>, delta frames can considerably reduce frame size and are used in virtually every video compression <a href="/wiki/Codec" title="Codec">codec</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Definition">Definition</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=2" title="Edit section: Definition"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A delta can be defined in 2 ways, <i>symmetric delta</i> and <i>directed delta</i>. A <i>symmetric delta</i> can be expressed as </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Delta (v_{1},v_{2})=(v_{1}\setminus v_{2})\cup (v_{2}\setminus v_{1}),}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi mathvariant="normal">Δ</mi> <mo stretchy="false">(</mo> <msub> <mi>v</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> <mo>,</mo> <msub> <mi>v</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> <mo stretchy="false">)</mo> <mo>=</mo> <mo stretchy="false">(</mo> <msub> <mi>v</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> <mo class="MJX-variant">∖</mo> <msub> <mi>v</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> <mo stretchy="false">)</mo> <mo>∪</mo> <mo stretchy="false">(</mo> <msub> <mi>v</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> <mo class="MJX-variant">∖</mo> <msub> <mi>v</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> <mo stretchy="false">)</mo> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \Delta (v_{1},v_{2})=(v_{1}\setminus v_{2})\cup (v_{2}\setminus v_{1}),}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1a425d8d76660a70af5cb9e5a4cb887c87a429ab" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:32.206ex; height:2.843ex;" alt="{\displaystyle \Delta (v_{1},v_{2})=(v_{1}\setminus v_{2})\cup (v_{2}\setminus v_{1}),}"></span></dd></dl> <p>where <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle v_{1}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>v</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle v_{1}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/98d33f5d498d528bd8c10edc8ac8c34347f32b3a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.182ex; height:2.009ex;" alt="{\displaystyle v_{1}}"></span> and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle v_{2}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>v</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle v_{2}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/eb04c423c2cb809c30cac725befa14ffbf4c85f3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.182ex; height:2.009ex;" alt="{\displaystyle v_{2}}"></span> represent two versions. </p><p>A <i>directed delta</i>, also called a change, is a sequence of (elementary) change operations which, when applied to one version <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle v_{1}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>v</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle v_{1}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/98d33f5d498d528bd8c10edc8ac8c34347f32b3a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.182ex; height:2.009ex;" alt="{\displaystyle v_{1}}"></span>, yields another version <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle v_{2}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>v</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle v_{2}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/eb04c423c2cb809c30cac725befa14ffbf4c85f3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.182ex; height:2.009ex;" alt="{\displaystyle v_{2}}"></span> (note the correspondence to <a href="/wiki/Transaction_log" title="Transaction log">transaction logs</a> in databases). In computer implementations, they typically take the form of a language with two commands: <i>copy data from v1</i> and <i>write literal data</i>. </p> <div class="mw-heading mw-heading3"><h3 id="Variants">Variants</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=3" title="Edit section: Variants"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A variation of delta encoding which encodes differences between the <a href="/wiki/Prefix_(computer_science)" class="mw-redirect" title="Prefix (computer science)">prefixes</a> or <a href="/wiki/Suffix_(computer_science)" class="mw-redirect" title="Suffix (computer science)">suffixes</a> of <a href="/wiki/String_(computer_science)" title="String (computer science)">strings</a> is called <a href="/wiki/Incremental_encoding" title="Incremental encoding">incremental encoding</a>. It is particularly effective for sorted lists with small differences between strings, such as a list of <a href="/wiki/Word" title="Word">words</a> from a <a href="/wiki/Dictionary" title="Dictionary">dictionary</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Implementation_issues">Implementation issues</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=4" title="Edit section: Implementation issues"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The nature of the data to be encoded influences the effectiveness of a particular compression algorithm. </p><p>Delta encoding performs best when data has small or constant variation; for an unsorted data set, there may be little to no compression possible with this method. </p><p>In delta encoded transmission over a network where only a single copy of the file is available at each end of the communication channel, special <a href="/wiki/Error-correction" class="mw-redirect" title="Error-correction">error control codes</a> are used to detect which parts of the file have changed since its previous version. For example, <a href="/wiki/Rsync" title="Rsync">rsync</a> uses a rolling <a href="/wiki/Checksum" title="Checksum">checksum</a> algorithm based on Mark Adler's <a href="/wiki/Adler-32" title="Adler-32">adler-32</a> checksum. </p> <div class="mw-heading mw-heading2"><h2 id="Sample_C_code">Sample C code</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=5" title="Edit section: Sample C code"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The following <a href="/wiki/C_(programming_language)" title="C (programming language)">C</a> code performs a simple form of delta encoding and decoding on a sequence of characters: </p> <div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre><span></span><span class="kt">void</span><span class="w"> </span><span class="nf">delta_encode</span><span class="p">(</span><span class="kt">unsigned</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="o">*</span><span class="n">buffer</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">length</span><span class="p">)</span> <span class="p">{</span> <span class="w"> </span><span class="kt">unsigned</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span> <span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="kt">unsigned</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buffer</span><span class="p">[</span><span class="n">i</span><span class="p">];</span> <span class="w"> </span><span class="n">buffer</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">last</span><span class="p">;</span> <span class="w"> </span><span class="n">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">;</span> <span class="w"> </span><span class="p">}</span> <span class="p">}</span> <span class="kt">void</span><span class="w"> </span><span class="nf">delta_decode</span><span class="p">(</span><span class="kt">unsigned</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="o">*</span><span class="n">buffer</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">length</span><span class="p">)</span> <span class="p">{</span> <span class="w"> </span><span class="kt">unsigned</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span> <span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="kt">unsigned</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">delta</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buffer</span><span class="p">[</span><span class="n">i</span><span class="p">];</span> <span class="w"> </span><span class="n">buffer</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">delta</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">last</span><span class="p">;</span> <span class="w"> </span><span class="n">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buffer</span><span class="p">[</span><span class="n">i</span><span class="p">];</span> <span class="w"> </span><span class="p">}</span> <span class="p">}</span> </pre></div> <div class="mw-heading mw-heading2"><h2 id="Examples">Examples</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=6" title="Edit section: Examples"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Binary_delta_compression">Binary delta compression</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=7" title="Edit section: Binary delta compression"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="excerpt-block"><style data-mw-deduplicate="TemplateStyles:r1066933788">.mw-parser-output .excerpt-hat .mw-editsection-like{font-style:normal}</style><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable dablink excerpt-hat selfref">This section is an excerpt from <a href="/wiki/Binary_delta_compression" title="Binary delta compression">Binary delta compression</a>.<span class="mw-editsection-like plainlinks"><span class="mw-editsection-bracket">[</span><a class="external text" href="https://en.wikipedia.org/w/index.php?title=Binary_delta_compression&action=edit">edit</a><span class="mw-editsection-bracket">]</span></span></div><div class="excerpt"> <a href="/wiki/Binary_delta_compression" title="Binary delta compression">Binary delta compression</a> is a technology used in <a href="/wiki/Software_deployment" title="Software deployment">software deployment</a> for distributing <a href="/wiki/Patch_(software)" class="mw-redirect" title="Patch (software)">patches</a>.</div></div> <div class="mw-heading mw-heading3"><h3 id="Delta_encoding_in_HTTP">Delta encoding in HTTP</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=8" title="Edit section: Delta encoding in HTTP"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Another instance of use of delta encoding is <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc3229">RFC 3229</a>, "Delta encoding in HTTP", which proposes that <a href="/wiki/HTTP" title="HTTP">HTTP</a> servers should be able to send updated Web pages in the form of differences between versions (deltas), which should decrease Internet traffic, as most pages change slowly over time, rather than being completely rewritten repeatedly: </p> <style data-mw-deduplicate="TemplateStyles:r1244412712">.mw-parser-output .templatequote{overflow:hidden;margin:1em 0;padding:0 32px}.mw-parser-output .templatequotecite{line-height:1.5em;text-align:left;margin-top:0}@media(min-width:500px){.mw-parser-output .templatequotecite{padding-left:1.6em}}</style><blockquote class="templatequote"><p>This document describes how delta encoding can be supported as a compatible extension to HTTP/1.1. </p><p>Many HTTP (Hypertext Transport Protocol) requests cause the retrieval of slightly modified instances of resources for which the client already has a cache entry. Research has shown that such modifying updates are frequent, and that the modifications are typically much smaller than the actual entity. In such cases, HTTP would make more efficient use of network bandwidth if it could transfer a minimal description of the changes, rather than the entire new instance of the resource. </p><p>[...] We believe that it might be possible to support rsync using the "instance manipulation" framework described later in this document, but this has not been worked out in any detail. </p> </blockquote> <p>The suggested rsync-based framework was implemented in the <i>rproxy</i> system as a pair of HTTP proxies.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Like the basic vcdiff-based implementation, both systems are rarely used. </p> <div class="mw-heading mw-heading3"><h3 id="Delta_copying">Delta copying</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=9" title="Edit section: Delta copying"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><i>Delta copying</i> is a fast way of copying a file that is partially changed, when a previous version is present on the destination location. With delta copying, only the changed part of a file is copied. It is usually used in <a href="/wiki/Backup" title="Backup">backup</a> or <a href="/wiki/File_copying" title="File copying">file copying</a> software, often to save <a href="/wiki/Bandwidth_(computing)" title="Bandwidth (computing)">bandwidth</a> when copying between computers over a private network or the internet. One notable open-source example is <a href="/wiki/Rsync" title="Rsync">rsync</a>.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading4"><h4 id="Online_backup">Online backup</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=10" title="Edit section: Online backup"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Online_backup_services" class="mw-redirect" title="Online backup services">Online backup services</a></div> <p>Many of the <a href="/wiki/Online_backup_services" class="mw-redirect" title="Online backup services">online backup services</a> adopt this methodology, often known simply as <i>deltas</i>, in order to give their users previous versions of the same file from previous backups. This reduces associated costs, not only in the amount of data that has to be stored as differing versions (as the whole of each changed version of a file has to be offered for users to access), but also those costs in the uploading (and sometimes the downloading) of each file that has been updated (by just the smaller delta having to be used, rather than the whole file). </p> <div class="mw-heading mw-heading4"><h4 id="Delta_updates">Delta updates</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=11" title="Edit section: Delta updates"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Delta_update" title="Delta update">delta update</a></div> <p>For large software packages, there is usually little data changed between versions. Many vendors choose to use delta transfers to save time and bandwidth. </p> <div class="mw-heading mw-heading3"><h3 id="Diff">Diff</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=12" title="Edit section: Diff"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Diff" title="Diff">Diff</a></div> <p>Diff is a file comparison program, which is mainly used for text files. By default, it generates symmetric deltas that are reversible. Two formats used for software <a href="/wiki/Patch_(Unix)" title="Patch (Unix)">patches</a>, <i>context</i> and <i>unified</i>, provides additional context lines that allow for tolerating shifts in line number. </p> <div class="mw-heading mw-heading3"><h3 id="Git">Git</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=13" title="Edit section: Git"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Git_(software)" class="mw-redirect" title="Git (software)">Git (software)</a></div> <p>The Git source code control system employs delta compression in an auxiliary "<a rel="nofollow" class="external text" href="http://git-scm.com/docs/git-repack">git repack</a>" operation. Objects in the repository that have not yet been delta-compressed ("loose objects") are compared against a heuristically chosen subset of all other objects, and the common data and differences are concatenated into a "pack file" which is then compressed using conventional methods. In common use cases, where source or data files are changed incrementally between commits, this can result in significant space savings. The repack operation is typically performed as part of the " git gc"<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> process, which is triggered automatically when the numbers of loose objects or pack files exceed configured thresholds. </p><p>The format is documented in the pack-format page of the Git documentation. It implements a directed delta.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="VCDIFF">VCDIFF</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=14" title="Edit section: VCDIFF"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/VCDIFF" title="VCDIFF">VCDIFF</a></div> <p>One general format for directed delta encoding is VCDIFF, described in <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc3284">RFC 3284</a>. <a href="/wiki/Free_software" title="Free software">Free software</a> implementations include <a href="/wiki/Xdelta" title="Xdelta">Xdelta</a> and open-vcdiff. </p> <div class="mw-heading mw-heading3"><h3 id="GDIFF">GDIFF</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=15" title="Edit section: GDIFF"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Generic Diff Format (GDIFF) is another directed delta encoding format. It was submitted to <a href="/wiki/W3C" class="mw-redirect" title="W3C">W3C</a> in 1997.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> In many cases, VCDIFF has better compression rate than GDIFF. </p> <div class="mw-heading mw-heading3"><h3 id="bsdiff">bsdiff</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=16" title="Edit section: bsdiff"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Bsdiff is a binary diff program using <a href="/wiki/Suffix_array" title="Suffix array">suffix sorting</a>. For executables that contain many changes in pointer addresses, it performs better than VCDIFF-type "copy and literal" encodings. The intent is to find a way to generate a small diff without needing to parse assembly code (as in Google's Courgette). Bsdiff achieves this by allowing "copy" matches with errors, which are then corrected using an extra "add" array of bytewise differences. Since this array is mostly either zero or repeated values for offset changes, it takes up little space after compression.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>Bsdiff is useful for delta updates. Google uses bsdiff in Chromium and Android. The <i>deltarpm</i> feature of the <a href="/wiki/RPM_Package_Manager" title="RPM Package Manager">RPM Package Manager</a> is based on a heavily modified bsdiff that can use a hash table for matching.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> <a href="/wiki/FreeBSD" title="FreeBSD">FreeBSD</a> also uses bsdiff for updates.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>Since the 4.3 release of bsdiff in 2005, various improvements or fixes have been produced for it. Google maintains multiple versions of the code for each of its products.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> FreeBSD takes many of Google's compatible changes, mainly a vulnerability fix and a switch to the faster <code class="mw-highlight mw-highlight-lang-text mw-content-ltr" style="" dir="ltr">divsufsort</code> suffix-sorting routine.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Debian" title="Debian">Debian</a> has a series of performance tweaks to the program.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p><p><i>ddelta</i> is a rewrite of bsdiff proposed for use in Debian's delta updates. Among other efficiency improvements, it uses a sliding window to reduce memory and CPU cost.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=17" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Data_differencing" title="Data differencing">Data differencing</a> – Method for compressing changes over time</li> <li><a href="/wiki/Interleaved_deltas" title="Interleaved deltas">Interleaved deltas</a> – method used by SCCS to store all revisions of a file<span style="display:none" class="category-wikidata-fallback-annotation">Pages displaying wikidata descriptions as a fallback</span></li> <li><a href="/wiki/Source_Code_Control_System" title="Source Code Control System">Source Code Control System</a> – version control system designed to track changes in the source code<span style="display:none" class="category-wikidata-fallback-annotation">Pages displaying wikidata descriptions as a fallback</span></li> <li><a href="/wiki/String-to-string_correction_problem" title="String-to-string correction problem">String-to-string correction problem</a></li> <li><a href="/wiki/Xdelta" title="Xdelta">Xdelta</a>: open-source delta encoder</li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=18" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon 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Retrieved <span class="nowrap">November 9,</span> 2024</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.daemonology.net&rft.atitle=Binary+diff&rft_id=http%3A%2F%2Fwww.daemonology.net%2Fbsdiff%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelta+encoding" class="Z3988"></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://github.com/rpm-software-management/deltarpm/blob/c5e0ca7482e2cfea5e4d902ffe488e0a71ed3e67/delta.c">"rpmdelta/delta.c"</a>. rpm-software-management. 3 July 2019<span class="reference-accessdate">. Retrieved <span class="nowrap">13 January</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=rpmdelta%2Fdelta.c&rft.pub=rpm-software-management&rft.date=2019-07-03&rft_id=https%3A%2F%2Fgithub.com%2Frpm-software-management%2Fdeltarpm%2Fblob%2Fc5e0ca7482e2cfea5e4d902ffe488e0a71ed3e67%2Fdelta.c&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelta+encoding" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAnonymous2016" class="citation web cs1">Anonymous (May 2016). <a rel="nofollow" class="external text" href="https://gist.github.com/anonymous/e48209b03f1dd9625a992717e7b89c4f">"NON-CRYPTANALYTIC ATTACKS AGAINST FREEBSD UPDATE COMPONENTS"</a>. <i>GitHub Gist</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=GitHub+Gist&rft.atitle=NON-CRYPTANALYTIC+ATTACKS+AGAINST+FREEBSD+UPDATE+COMPONENTS&rft.date=2016-05&rft.au=Anonymous&rft_id=https%3A%2F%2Fgist.github.com%2Fanonymous%2Fe48209b03f1dd9625a992717e7b89c4f&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelta+encoding" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://github.com/xtraeme/bsdiff-chromium/blob/master/README.chromium">"xtraeme/bsdiff-chromium: README.chromium"</a>. <i>GitHub</i>. 2012.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=GitHub&rft.atitle=xtraeme%2Fbsdiff-chromium%3A+README.chromium&rft.date=2012&rft_id=https%3A%2F%2Fgithub.com%2Fxtraeme%2Fbsdiff-chromium%2Fblob%2Fmaster%2FREADME.chromium&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelta+encoding" class="Z3988"></span>; <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://chromium.googlesource.com/chromium/src/+/master/courgette/third_party/bsdiff/README.chromium">"courgette/third_party/bsdiff/README.chromium - chromium/src"</a>. <i>Git at Google</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Git+at+Google&rft.atitle=courgette%2Fthird_party%2Fbsdiff%2FREADME.chromium+-+chromium%2Fsrc&rft_id=https%3A%2F%2Fchromium.googlesource.com%2Fchromium%2Fsrc%2F%2B%2Fmaster%2Fcourgette%2Fthird_party%2Fbsdiff%2FREADME.chromium&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelta+encoding" class="Z3988"></span>; <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://android.googlesource.com/platform/external/bsdiff/+/refs/heads/master">"android/platform/external/bsdiff/"</a>. <i>Git at Google</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Git+at+Google&rft.atitle=android%2Fplatform%2Fexternal%2Fbsdiff%2F&rft_id=https%3A%2F%2Fandroid.googlesource.com%2Fplatform%2Fexternal%2Fbsdiff%2F%2B%2Frefs%2Fheads%2Fmaster&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelta+encoding" class="Z3988"></span></span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://github.com/freebsd/freebsd/commits/master/usr.bin/bsdiff">"History for freebsd/usr.bin/bsdiff"</a>. <i>GitHub</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=GitHub&rft.atitle=History+for+freebsd%2Fusr.bin%2Fbsdiff&rft_id=https%3A%2F%2Fgithub.com%2Ffreebsd%2Ffreebsd%2Fcommits%2Fmaster%2Fusr.bin%2Fbsdiff&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelta+encoding" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://sources.debian.org/patches/bsdiff/">"Package: bsdiff"</a>. <i>Debian Patch Tracker</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Debian+Patch+Tracker&rft.atitle=Package%3A+bsdiff&rft_id=https%3A%2F%2Fsources.debian.org%2Fpatches%2Fbsdiff%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelta+encoding" class="Z3988"></span></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKlode" class="citation web cs1">Klode, Julian. <a rel="nofollow" class="external text" href="https://github.com/julian-klode/ddelta">"julian-klode/ddelta"</a>. <i>GitHub</i><span class="reference-accessdate">. Retrieved <span class="nowrap">13 January</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=GitHub&rft.atitle=julian-klode%2Fddelta&rft.aulast=Klode&rft.aufirst=Julian&rft_id=https%3A%2F%2Fgithub.com%2Fjulian-klode%2Fddelta&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelta+encoding" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delta_encoding&action=edit&section=19" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222">RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc3229">3229</a> – Delta Encoding in HTTP</li></ul> <div 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abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Compression_methods" title="Template:Compression methods"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Compression_methods" title="Template talk:Compression methods"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Compression_methods" title="Special:EditPage/Template:Compression methods"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Data_compression_methods223" style="font-size:114%;margin:0 4em"><a href="/wiki/Data_compression" title="Data compression">Data compression</a> methods</div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Lossless_compression" title="Lossless compression">Lossless</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:7.0em;font-weight:normal;"><a href="/wiki/Entropy_coding" title="Entropy coding">Entropy type</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Adaptive_coding" title="Adaptive coding">Adaptive coding</a></li> <li><a href="/wiki/Arithmetic_coding" title="Arithmetic coding">Arithmetic</a></li> <li><a href="/wiki/Asymmetric_numeral_systems" title="Asymmetric numeral systems">Asymmetric numeral systems</a></li> <li><a href="/wiki/Golomb_coding" title="Golomb coding">Golomb</a></li> <li><a href="/wiki/Huffman_coding" title="Huffman coding">Huffman</a> <ul><li><a href="/wiki/Adaptive_Huffman_coding" title="Adaptive Huffman coding">Adaptive</a></li> <li><a href="/wiki/Canonical_Huffman_code" title="Canonical Huffman code">Canonical</a></li> <li><a href="/wiki/Modified_Huffman_coding" title="Modified Huffman coding">Modified</a></li></ul></li> <li><a href="/wiki/Range_coding" title="Range coding">Range</a></li> <li><a href="/wiki/Shannon_coding" title="Shannon coding">Shannon</a></li> <li><a href="/wiki/Shannon%E2%80%93Fano_coding" title="Shannon–Fano coding">Shannon–Fano</a></li> <li><a href="/wiki/Shannon%E2%80%93Fano%E2%80%93Elias_coding" title="Shannon–Fano–Elias coding">Shannon–Fano–Elias</a></li> <li><a href="/wiki/Tunstall_coding" title="Tunstall coding">Tunstall</a></li> <li><a href="/wiki/Unary_coding" title="Unary coding">Unary</a></li> <li><a href="/wiki/Universal_code_(data_compression)" title="Universal code (data compression)">Universal</a> <ul><li><a href="/wiki/Exponential-Golomb_coding" title="Exponential-Golomb coding">Exp-Golomb</a></li> <li><a href="/wiki/Fibonacci_coding" title="Fibonacci coding">Fibonacci</a></li> <li><a href="/wiki/Elias_gamma_coding" title="Elias gamma coding">Gamma</a></li> <li><a href="/wiki/Levenshtein_coding" title="Levenshtein coding">Levenshtein</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:7.0em;font-weight:normal;"><a href="/wiki/Dictionary_coder" title="Dictionary coder">Dictionary type</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Byte_pair_encoding" title="Byte pair encoding">Byte pair encoding</a></li> <li><a href="/wiki/LZ77_and_LZ78" title="LZ77 and LZ78">Lempel–Ziv</a> <ul><li><a href="/wiki/842_(compression_algorithm)" title="842 (compression algorithm)">842</a></li> <li><a href="/wiki/LZ4_(compression_algorithm)" title="LZ4 (compression algorithm)">LZ4</a></li> <li><a href="/wiki/LZJB" class="mw-redirect" title="LZJB">LZJB</a></li> <li><a href="/wiki/Lempel%E2%80%93Ziv%E2%80%93Oberhumer" title="Lempel–Ziv–Oberhumer">LZO</a></li> <li><a href="/wiki/LZRW" title="LZRW">LZRW</a></li> <li><a href="/wiki/Lempel%E2%80%93Ziv%E2%80%93Storer%E2%80%93Szymanski" title="Lempel–Ziv–Storer–Szymanski">LZSS</a></li> <li><a href="/wiki/Lempel%E2%80%93Ziv%E2%80%93Welch" title="Lempel–Ziv–Welch">LZW</a></li> <li><a href="/wiki/LZWL" title="LZWL">LZWL</a></li> <li><a href="/wiki/Snappy_(compression)" title="Snappy (compression)">Snappy</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:7.0em;font-weight:normal;">Other types</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Burrows%E2%80%93Wheeler_transform" title="Burrows–Wheeler transform">BWT</a></li> <li><a href="/wiki/Context_tree_weighting" title="Context tree weighting">CTW</a></li> <li><a href="/wiki/Context_mixing" title="Context mixing">CM</a></li> <li><a class="mw-selflink selflink">Delta</a> <ul><li><a href="/wiki/Incremental_encoding" title="Incremental encoding">Incremental</a></li></ul></li> <li><a href="/wiki/Dynamic_Markov_compression" title="Dynamic Markov compression">DMC</a></li> <li><a href="/wiki/Differential_pulse-code_modulation" title="Differential pulse-code modulation">DPCM</a></li> <li><a href="/wiki/Grammar-based_code" title="Grammar-based code">Grammar</a> <ul><li><a href="/wiki/Re-Pair" title="Re-Pair">Re-Pair</a></li> <li><a href="/wiki/Sequitur_algorithm" title="Sequitur algorithm">Sequitur</a></li></ul></li> <li><a href="/wiki/Discrete_cosine_transform" title="Discrete cosine transform">LDCT</a></li> <li><a href="/wiki/Move-to-front_transform" title="Move-to-front transform">MTF</a></li> <li><a href="/wiki/PAQ" title="PAQ">PAQ</a></li> <li><a href="/wiki/Prediction_by_partial_matching" title="Prediction by partial matching">PPM</a></li> <li><a href="/wiki/Run-length_encoding" title="Run-length encoding">RLE</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:7.0em;font-weight:normal;">Hybrid</th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li>LZ77 + Huffman <ul><li><a href="/wiki/Deflate" title="Deflate">Deflate</a></li> <li><a href="/wiki/LZX" title="LZX">LZX</a></li> <li><a href="/wiki/Lempel%E2%80%93Ziv%E2%80%93Stac" title="Lempel–Ziv–Stac">LZS</a></li></ul></li> <li>LZ77 + ANS <ul><li><a href="/wiki/LZFSE" title="LZFSE">LZFSE</a></li></ul></li> <li>LZ77 + Huffman + ANS <ul><li><a href="/wiki/Zstd" title="Zstd">Zstandard</a></li></ul></li> <li>LZ77 + Huffman + context <ul><li><a href="/wiki/Brotli" title="Brotli">Brotli</a></li></ul></li> <li>LZSS + Huffman <ul><li><a href="/wiki/LHA_(file_format)" title="LHA (file format)">LHA/LZH</a></li></ul></li> <li>LZ77 + Range <ul><li><a href="/wiki/Lempel%E2%80%93Ziv%E2%80%93Markov_chain_algorithm" title="Lempel–Ziv–Markov chain algorithm">LZMA</a></li> <li>LZHAM</li></ul></li> <li>RLE + BWT + MTF + Huffman <ul><li><a href="/wiki/Bzip2" title="Bzip2">bzip2</a></li></ul></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Lossy_compression" title="Lossy compression">Lossy</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:7.0em;font-weight:normal;"><a href="/wiki/Transform_coding" title="Transform coding">Transform type</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Discrete_cosine_transform" title="Discrete cosine transform">Discrete cosine transform</a> <ul><li><a href="/wiki/Discrete_cosine_transform" title="Discrete cosine transform">DCT</a></li> <li><a href="/wiki/Modified_discrete_cosine_transform" title="Modified discrete cosine transform">MDCT</a></li></ul></li> <li><a href="/wiki/Discrete_sine_transform" title="Discrete sine transform">DST</a></li> <li><a href="/wiki/Fast_Fourier_transform" title="Fast Fourier transform">FFT</a></li> <li><a href="/wiki/Wavelet_transform" title="Wavelet transform">Wavelet</a> <ul><li><a href="/wiki/Daubechies_wavelet" title="Daubechies wavelet">Daubechies</a></li> <li><a href="/wiki/Discrete_wavelet_transform" title="Discrete wavelet transform">DWT</a></li> <li><a href="/wiki/Set_partitioning_in_hierarchical_trees" title="Set partitioning in hierarchical trees">SPIHT</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:7.0em;font-weight:normal;">Predictive type</th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Differential_pulse-code_modulation" title="Differential pulse-code modulation">DPCM</a> <ul><li><a href="/wiki/Adaptive_differential_pulse-code_modulation" title="Adaptive differential pulse-code modulation">ADPCM</a></li></ul></li> <li><a href="/wiki/Linear_predictive_coding" title="Linear predictive coding">LPC</a> <ul><li><a href="/wiki/Algebraic_code-excited_linear_prediction" title="Algebraic code-excited linear prediction">ACELP</a></li> <li><a href="/wiki/Code-excited_linear_prediction" title="Code-excited linear prediction">CELP</a></li> <li><a href="/wiki/Log_area_ratio" title="Log area ratio">LAR</a></li> <li><a href="/wiki/Line_spectral_pairs" title="Line spectral pairs">LSP</a></li> <li><a href="/wiki/Warped_linear_predictive_coding" title="Warped linear predictive coding">WLPC</a></li></ul></li> <li>Motion <ul><li><a href="/wiki/Motion_compensation" title="Motion compensation">Compensation</a></li> <li><a href="/wiki/Motion_estimation" title="Motion estimation">Estimation</a></li> <li><a href="/wiki/Motion_vector" class="mw-redirect" title="Motion vector">Vector</a></li></ul></li> <li><a href="/wiki/Psychoacoustics" title="Psychoacoustics">Psychoacoustic</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Data_compression#Audio" title="Data compression">Audio</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:7.0em;font-weight:normal;">Concepts</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Bit_rate" title="Bit rate">Bit rate</a> <ul><li><a href="/wiki/Average_bitrate" title="Average bitrate">ABR</a></li> <li><a href="/wiki/Constant_bitrate" title="Constant bitrate">CBR</a></li> <li><a href="/wiki/Variable_bitrate" title="Variable bitrate">VBR</a></li></ul></li> <li><a href="/wiki/Companding" title="Companding">Companding</a></li> <li><a href="/wiki/Convolution" title="Convolution">Convolution</a></li> <li><a href="/wiki/Dynamic_range" title="Dynamic range">Dynamic range</a></li> <li><a href="/wiki/Latency_(audio)" title="Latency (audio)">Latency</a></li> <li><a href="/wiki/Nyquist%E2%80%93Shannon_sampling_theorem" title="Nyquist–Shannon sampling theorem">Nyquist–Shannon theorem</a></li> <li><a href="/wiki/Sampling_(signal_processing)" title="Sampling (signal processing)">Sampling</a></li> <li><a href="/wiki/Silence_compression" title="Silence compression">Silence compression</a></li> <li><a href="/wiki/Sound_quality" title="Sound quality">Sound quality</a></li> <li><a href="/wiki/Speech_coding" title="Speech coding">Speech coding</a></li> <li><a href="/wiki/Sub-band_coding" title="Sub-band coding">Sub-band coding</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:7.0em;font-weight:normal;"><a href="/wiki/Audio_codec" title="Audio codec">Codec</a> parts</th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/A-law_algorithm" title="A-law algorithm">A-law</a></li> <li><a href="/wiki/%CE%9C-law_algorithm" title="Μ-law algorithm">μ-law</a></li> <li><a href="/wiki/Differential_pulse-code_modulation" title="Differential pulse-code modulation">DPCM</a> <ul><li><a href="/wiki/Adaptive_differential_pulse-code_modulation" title="Adaptive differential pulse-code modulation">ADPCM</a></li> <li><a href="/wiki/Delta_modulation" title="Delta modulation">DM</a></li></ul></li> <li><a href="/wiki/Fourier_transform" title="Fourier transform">FT</a> <ul><li><a href="/wiki/Fast_Fourier_transform" title="Fast Fourier transform">FFT</a></li></ul></li> <li><a href="/wiki/Linear_predictive_coding" title="Linear predictive coding">LPC</a> <ul><li><a href="/wiki/Algebraic_code-excited_linear_prediction" title="Algebraic code-excited linear prediction">ACELP</a></li> <li><a href="/wiki/Code-excited_linear_prediction" title="Code-excited linear prediction">CELP</a></li> <li><a href="/wiki/Log_area_ratio" title="Log area ratio">LAR</a></li> <li><a href="/wiki/Line_spectral_pairs" title="Line spectral pairs">LSP</a></li> <li><a href="/wiki/Warped_linear_predictive_coding" title="Warped linear predictive coding">WLPC</a></li></ul></li> <li><a href="/wiki/Modified_discrete_cosine_transform" title="Modified discrete cosine transform">MDCT</a></li> <li><a href="/wiki/Psychoacoustics" title="Psychoacoustics">Psychoacoustic model</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Image_compression" title="Image compression">Image</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:7.0em;font-weight:normal;">Concepts</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Chroma_subsampling" title="Chroma subsampling">Chroma subsampling</a></li> <li><a href="/wiki/Coding_tree_unit" title="Coding tree unit">Coding tree unit</a></li> <li><a href="/wiki/Color_space" title="Color space">Color space</a></li> <li><a href="/wiki/Compression_artifact" title="Compression artifact">Compression artifact</a></li> <li><a href="/wiki/Image_resolution" title="Image resolution">Image resolution</a></li> <li><a href="/wiki/Macroblock" title="Macroblock">Macroblock</a></li> <li><a href="/wiki/Pixel" title="Pixel">Pixel</a></li> <li><a href="/wiki/Peak_signal-to-noise_ratio" title="Peak signal-to-noise ratio">PSNR</a></li> <li><a href="/wiki/Quantization_(image_processing)" title="Quantization (image processing)">Quantization</a></li> <li><a href="/wiki/Standard_test_image" title="Standard test image">Standard test image</a></li> <li><a href="/wiki/Texture_compression" title="Texture compression">Texture compression</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:7.0em;font-weight:normal;">Methods</th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Chain_code" title="Chain code">Chain code</a></li> <li><a href="/wiki/Discrete_cosine_transform" title="Discrete cosine transform">DCT</a></li> <li><a href="/wiki/Deflate" title="Deflate">Deflate</a></li> <li><a href="/wiki/Fractal_compression" title="Fractal compression">Fractal</a></li> <li><a href="/wiki/Karhunen%E2%80%93Lo%C3%A8ve_theorem" class="mw-redirect" title="Karhunen–Loève theorem">KLT</a></li> <li><a href="/wiki/Pyramid_(image_processing)" title="Pyramid (image processing)">LP</a></li> <li><a href="/wiki/Run-length_encoding" title="Run-length encoding">RLE</a></li> <li><a href="/wiki/Wavelet_transform" title="Wavelet transform">Wavelet</a> <ul><li><a href="/wiki/Daubechies_wavelet" title="Daubechies wavelet">Daubechies</a></li> <li><a href="/wiki/Discrete_wavelet_transform" title="Discrete wavelet transform">DWT</a></li> <li><a href="/wiki/Embedded_zerotrees_of_wavelet_transforms" title="Embedded zerotrees of wavelet transforms">EZW</a></li> <li><a href="/wiki/Set_partitioning_in_hierarchical_trees" title="Set partitioning in hierarchical trees">SPIHT</a></li></ul></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Data_compression#Video" title="Data compression">Video</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:7.0em;font-weight:normal;">Concepts</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Bit_rate" title="Bit rate">Bit rate</a> <ul><li><a href="/wiki/Average_bitrate" title="Average bitrate">ABR</a></li> <li><a href="/wiki/Constant_bitrate" title="Constant bitrate">CBR</a></li> <li><a href="/wiki/Variable_bitrate" title="Variable bitrate">VBR</a></li></ul></li> <li><a href="/wiki/Display_resolution" title="Display resolution">Display resolution</a></li> <li><a href="/wiki/Film_frame" title="Film frame">Frame</a></li> <li><a href="/wiki/Frame_rate" title="Frame rate">Frame rate</a></li> <li><a href="/wiki/Video_compression_picture_types" title="Video compression picture types">Frame types</a></li> <li><a href="/wiki/Interlaced_video" title="Interlaced video">Interlace</a></li> <li><a href="/wiki/Video#Characteristics_of_video_streams" title="Video">Video characteristics</a></li> <li><a href="/wiki/Video_quality" title="Video quality">Video quality</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:7.0em;font-weight:normal;"><a href="/wiki/Video_codec" title="Video codec">Codec</a> parts</th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Discrete_cosine_transform" title="Discrete cosine transform">DCT</a></li> <li><a href="/wiki/Differential_pulse-code_modulation" title="Differential pulse-code modulation">DPCM</a></li> <li><a href="/wiki/Deblocking_filter" title="Deblocking filter">Deblocking filter</a></li> <li><a href="/wiki/Lapped_transform" title="Lapped transform">Lapped transform</a></li> <li>Motion <ul><li><a href="/wiki/Motion_compensation" title="Motion compensation">Compensation</a></li> <li><a href="/wiki/Motion_estimation" title="Motion estimation">Estimation</a></li> <li><a href="/wiki/Motion_vector" class="mw-redirect" title="Motion vector">Vector</a></li></ul></li> <li><a href="/wiki/Wavelet_transform" title="Wavelet transform">Wavelet</a> <ul><li><a href="/wiki/Daubechies_wavelet" title="Daubechies wavelet">Daubechies</a></li> <li><a href="/wiki/Discrete_wavelet_transform" title="Discrete wavelet transform">DWT</a></li></ul></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Information_theory" title="Information theory">Theory</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Compressed_data_structure" title="Compressed data structure">Compressed data structures</a> <ul><li><a href="/wiki/Compressed_suffix_array" title="Compressed suffix array">Compressed suffix array</a></li> <li><a href="/wiki/FM-index" title="FM-index">FM-index</a></li></ul></li> <li><a href="/wiki/Entropy_(information_theory)" title="Entropy (information theory)">Entropy</a></li> <li><a href="/wiki/Information_theory" title="Information theory">Information theory</a> <ul><li><a href="/wiki/Timeline_of_information_theory" title="Timeline of information theory">Timeline</a></li></ul></li> <li><a href="/wiki/Kolmogorov_complexity" title="Kolmogorov complexity">Kolmogorov complexity</a></li> <li><a href="/wiki/Prefix_code" title="Prefix code">Prefix code</a></li> <li><a href="/wiki/Quantization_(signal_processing)" title="Quantization (signal processing)">Quantization</a></li> <li><a href="/wiki/Rate%E2%80%93distortion_theory" title="Rate–distortion theory">Rate–distortion</a></li> <li><a href="/wiki/Redundancy_(information_theory)" title="Redundancy (information theory)">Redundancy</a></li> <li><a href="/wiki/Data_compression_symmetry" title="Data compression symmetry">Symmetry</a></li> <li><a href="/wiki/Smallest_grammar_problem" title="Smallest grammar problem">Smallest grammar problem</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Community</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Hutter_Prize" title="Hutter Prize">Hutter Prize</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">People</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Mark_Adler" title="Mark Adler">Mark Adler</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Version_control_software443" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="3"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Version_control_software" title="Template:Version control software"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Version_control_software" title="Template talk:Version control software"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Version_control_software" title="Special:EditPage/Template:Version control software"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Version_control_software443" style="font-size:114%;margin:0 4em"><a href="/wiki/Version_control" title="Version control">Version control software</a></div></th></tr><tr><td class="navbox-abovebelow" colspan="3"><div>Years, where available, indicate the date of first stable release. Systems with names <i>in italics</i> are no longer maintained or have planned end-of-life dates.</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Local only</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Free_and_open-source_software" title="Free and open-source software">Free/open-source</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Revision_Control_System" title="Revision Control System">RCS</a> (1982)</li> <li><a href="/wiki/Source_Code_Control_System" title="Source Code Control System">SCCS</a> (1973)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Proprietary_software" title="Proprietary software">Proprietary</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/The_Librarian_(version_control_system)" title="The Librarian (version control system)">The Librarian</a> (1969)</li> <li><a href="/wiki/Panvalet" title="Panvalet">Panvalet</a> (1970s)</li> <li><a href="/wiki/PVCS" title="PVCS">PVCS</a> (1985)</li> <li><i><a href="/wiki/QVCS" title="QVCS">QVCS</a></i> (1991)</li></ul> </div></td></tr></tbody></table><div></div></td><td class="noviewer navbox-image" rowspan="4" style="width:1px;padding:0 0 0 2px"><div><span typeof="mw:File"><a href="/wiki/File:Revision_controlled_project_visualization-2010-24-02.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/af/Revision_controlled_project_visualization-2010-24-02.svg/80px-Revision_controlled_project_visualization-2010-24-02.svg.png" decoding="async" width="80" height="196" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/af/Revision_controlled_project_visualization-2010-24-02.svg/120px-Revision_controlled_project_visualization-2010-24-02.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/af/Revision_controlled_project_visualization-2010-24-02.svg/160px-Revision_controlled_project_visualization-2010-24-02.svg.png 2x" data-file-width="220" data-file-height="540" /></a></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Client–server</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%">Free/open-source</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Concurrent_Versions_System" title="Concurrent Versions System">CVS</a> (1986, 1990 in C)</li> <li><a href="/wiki/CVSNT" title="CVSNT">CVSNT</a> (1998)</li> <li><a href="/wiki/QVCS" title="QVCS">QVCS Enterprise</a> (1998)</li> <li><a href="/wiki/Apache_Subversion" title="Apache Subversion">Subversion</a> (2000)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Proprietary</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/AccuRev_SCM" title="AccuRev SCM">AccuRev SCM</a> (2002)</li> <li>Azure DevOps <ul><li><a href="/wiki/Azure_DevOps_Server" title="Azure DevOps Server">Server</a> (via <a href="/wiki/Azure_DevOps_Server#TFVC" title="Azure DevOps Server">TFVC</a>) (2005)</li> <li><a href="/wiki/Microsoft_Visual_Studio#Azure_DevOps_Services" class="mw-redirect" title="Microsoft Visual Studio">Services</a> (via <a href="/wiki/Azure_DevOps_Server#TFVC" title="Azure DevOps Server">TFVC</a>) (2014)</li></ul></li> <li><a href="/wiki/Rational_ClearCase" class="mw-redirect" title="Rational ClearCase">ClearCase</a> (1992)</li> <li><i><a href="/wiki/IBM_Configuration_Management_Version_Control_(CMVC)" class="mw-redirect" title="IBM Configuration Management Version Control (CMVC)">CMVC</a></i> (1994)</li> <li><a href="/wiki/Dimensions_CM" title="Dimensions CM">Dimensions CM</a> (1980s)</li> <li><i><a href="/wiki/Apollo_Computer#History" title="Apollo Computer">DSEE</a></i> (1984)</li> <li><a href="/wiki/PTC_Integrity" title="PTC Integrity">Integrity</a> (2001)</li> <li><a href="/wiki/Perforce_Helix" class="mw-redirect" title="Perforce Helix">Perforce Helix</a> (1995)</li> <li><a href="/wiki/IBM_Software_Configuration_and_Library_Manager" title="IBM Software Configuration and Library Manager">SCLM</a> (1980s?)</li> <li><a href="/wiki/CA_Harvest_Software_Change_Manager" title="CA Harvest Software Change Manager">Software Change Manager</a> (1970s)</li> <li><a href="/wiki/StarTeam" title="StarTeam">StarTeam</a> (1995)</li> <li><a href="/wiki/Surround_SCM" title="Surround SCM">Surround SCM</a> (2002)</li> <li><a href="/wiki/Rational_Synergy" title="Rational Synergy">Synergy</a> (1990)</li> <li><a href="/wiki/Rational_Team_Concert" class="mw-redirect" title="Rational Team Concert">Team Concert</a> (2008)</li> <li><a href="/wiki/Vault_(version_control_system)" title="Vault (version control system)">Vault</a> (2003)</li> <li><i><a href="/wiki/Microsoft_Visual_SourceSafe" title="Microsoft Visual SourceSafe">Visual SourceSafe</a></i> (1994)</li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Distributed_version_control" title="Distributed version control">Distributed</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%">Free/open-source</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><i><a href="/wiki/BitKeeper" title="BitKeeper">BitKeeper</a></i> (2000)</li> <li><a href="/wiki/Breezy_(software)" title="Breezy (software)">Breezy</a> (2017)</li> <li><i><a href="/wiki/Code_Co-op" title="Code Co-op">Code Co-op</a></i> (1997)</li> <li><a href="/wiki/Darcs" title="Darcs">Darcs</a> (2002)</li> <li><i><a href="/wiki/Distributed_Concurrent_Versions_System" title="Distributed Concurrent Versions System">DCVS</a></i> (2002)</li> <li><a href="/wiki/Fossil_(software)" title="Fossil (software)">Fossil</a> (2007)</li> <li><a href="/wiki/Git" title="Git">Git</a> (2005)</li> <li><i><a href="/wiki/GNU_arch" title="GNU arch">GNU arch</a></i> (2001)</li> <li><a href="/wiki/GNU_Bazaar" title="GNU Bazaar">GNU Bazaar</a> (2005)</li> <li><a href="/wiki/Mercurial" title="Mercurial">Mercurial</a> (2005)</li> <li><a href="/wiki/Monotone_(software)" title="Monotone (software)">Monotone</a> (2003)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Proprietary</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li>Azure DevOps <ul><li><a href="/wiki/Azure_DevOps_Server" title="Azure DevOps Server">Server</a> (via Git) (2013)</li> <li><a href="/wiki/Microsoft_Visual_Studio#Azure_DevOps_Services" class="mw-redirect" title="Microsoft Visual Studio">Services</a> (via Git) (2014)</li></ul></li> <li><i><a href="/wiki/Sun_WorkShop_TeamWare" title="Sun WorkShop TeamWare">TeamWare</a></i> (1992)</li> <li><a href="/wiki/Plastic_SCM" class="mw-redirect" title="Plastic SCM">Plastic SCM</a> (2006)</li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Concepts</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Baseline_(configuration_management)" title="Baseline (configuration management)">Baseline</a></li> <li><a href="/wiki/Branching_(version_control)" title="Branching (version control)">Branch</a> <ul><li><a href="/wiki/Branching_(version_control)#Development_branch" title="Branching (version control)">Trunk</a></li></ul></li> <li><a href="/wiki/Changeset" title="Changeset">Changeset</a></li> <li><a href="/wiki/Commit_(version_control)" title="Commit (version control)">Commit</a> <ul><li><a href="/wiki/Gated_commit" title="Gated commit">Gated</a></li></ul></li> <li><a class="mw-selflink selflink">Delta compression</a> <ul><li><a href="/wiki/Interleaved_deltas" title="Interleaved deltas">Interleaved</a></li></ul></li> <li><a href="/wiki/File_comparison" title="File comparison">File comparison</a></li> <li><a href="/wiki/Fork_(software_development)" title="Fork (software development)">Fork</a></li> <li><a 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