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  1. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

  2. <html>

  3. <!-- Created by GNU Texinfo 6.8, https://www.gnu.org/software/texinfo/ -->

  4.   <head>

  5.     <meta charset="utf-8">

  6.     <title>

  7.       FFmpeg Utilities Documentation

  8.     </title>

  9.     <meta name="viewport" content="width=device-width,initial-scale=1.0">

  10.     <link rel="stylesheet" type="text/css" href="bootstrap.min.css">

  11.     <link rel="stylesheet" type="text/css" href="style.min.css">

  12.   </head>

  13.   <body>

  14.     <div class="container">

  15.       <h1>

  16.       FFmpeg Utilities Documentation

  17.       </h1>

  18. <div align="center">

  19. </div>

  20. 

  21. 

  22. <a name="SEC_Top"></a>

  23. 

  24. <div class="Contents_element" id="SEC_Contents">

  25. <h2 class="contents-heading">Table of Contents</h2>

  26. 

  27. <div class="contents">

  28. 

  29. <ul class="no-bullet">

  30.   <li><a id="toc-Description" href="#Description">1 Description</a></li>

  31.   <li><a id="toc-Syntax" href="#Syntax">2 Syntax</a>

  32.   <ul class="no-bullet">

  33.     <li><a id="toc-Quoting-and-escaping" href="#Quoting-and-escaping">2.1 Quoting and escaping</a>

  34.     <ul class="no-bullet">

  35.       <li><a id="toc-Examples" href="#Examples">2.1.1 Examples</a></li>

  36.     </ul></li>

  37.     <li><a id="toc-Date" href="#Date">2.2 Date</a></li>

  38.     <li><a id="toc-Time-duration" href="#Time-duration">2.3 Time duration</a>

  39.     <ul class="no-bullet">

  40.       <li><a id="toc-Examples-1" href="#Examples-1">2.3.1 Examples</a></li>

  41.     </ul></li>

  42.     <li><a id="toc-Video-size" href="#Video-size">2.4 Video size</a></li>

  43.     <li><a id="toc-Video-rate" href="#Video-rate">2.5 Video rate</a></li>

  44.     <li><a id="toc-Ratio" href="#Ratio">2.6 Ratio</a></li>

  45.     <li><a id="toc-Color" href="#Color">2.7 Color</a></li>

  46.     <li><a id="toc-Channel-Layout" href="#Channel-Layout">2.8 Channel Layout</a></li>

  47.   </ul></li>

  48.   <li><a id="toc-Expression-Evaluation" href="#Expression-Evaluation">3 Expression Evaluation</a></li>

  49.   <li><a id="toc-See-Also" href="#See-Also">4 See Also</a></li>

  50.   <li><a id="toc-Authors" href="#Authors">5 Authors</a></li>

  51. </ul>

  52. </div>

  53. </div>

  54. 

  55. <a name="Description"></a>

  56. <h2 class="chapter">1 Description<span class="pull-right"><a class="anchor hidden-xs" href="#Description" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Description" aria-hidden="true">TOC</a></span></h2>

  57. 

  58. <p>This document describes some generic features and utilities provided

  59. by the libavutil library.

  60. </p>

  61. 

  62. <a name="Syntax"></a>

  63. <h2 class="chapter">2 Syntax<span class="pull-right"><a class="anchor hidden-xs" href="#Syntax" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Syntax" aria-hidden="true">TOC</a></span></h2>

  64. 

  65. <p>This section documents the syntax and formats employed by the FFmpeg

  66. libraries and tools.

  67. </p>

  68. <span id="quoting_005fand_005fescaping"></span><a name="Quoting-and-escaping"></a>

  69. <h3 class="section">2.1 Quoting and escaping<span class="pull-right"><a class="anchor hidden-xs" href="#Quoting-and-escaping" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Quoting-and-escaping" aria-hidden="true">TOC</a></span></h3>

  70. 

  71. <p>FFmpeg adopts the following quoting and escaping mechanism, unless

  72. explicitly specified. The following rules are applied:

  73. </p>

  74. <ul>

  75. <li> &lsquo;<samp>'</samp>&rsquo; and &lsquo;<samp>\</samp>&rsquo; are special characters (respectively used for

  76. quoting and escaping). In addition to them, there might be other

  77. special characters depending on the specific syntax where the escaping

  78. and quoting are employed.

  79. 

  80. </li><li> A special character is escaped by prefixing it with a &lsquo;<samp>\</samp>&rsquo;.

  81. 

  82. </li><li> All characters enclosed between &lsquo;<samp>''</samp>&rsquo; are included literally in the

  83. parsed string. The quote character &lsquo;<samp>'</samp>&rsquo; itself cannot be quoted,

  84. so you may need to close the quote and escape it.

  85. 

  86. </li><li> Leading and trailing whitespaces, unless escaped or quoted, are

  87. removed from the parsed string.

  88. </li></ul>

  89. 

  90. <p>Note that you may need to add a second level of escaping when using

  91. the command line or a script, which depends on the syntax of the

  92. adopted shell language.

  93. </p>

  94. <p>The function <code>av_get_token</code> defined in

  95. <samp>libavutil/avstring.h</samp> can be used to parse a token quoted or

  96. escaped according to the rules defined above.

  97. </p>

  98. <p>The tool <samp>tools/ffescape</samp> in the FFmpeg source tree can be used

  99. to automatically quote or escape a string in a script.

  100. </p>

  101. <a name="Examples"></a>

  102. <h4 class="subsection">2.1.1 Examples<span class="pull-right"><a class="anchor hidden-xs" href="#Examples" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Examples" aria-hidden="true">TOC</a></span></h4>

  103. 

  104. <ul>

  105. <li> Escape the string <code>Crime d'Amour</code> containing the <code>'</code> special

  106. character:

  107. <div class="example">

  108. <pre class="example">Crime d\'Amour

  109. </pre></div>

  110. 

  111. </li><li> The string above contains a quote, so the <code>'</code> needs to be escaped

  112. when quoting it:

  113. <div class="example">

  114. <pre class="example">'Crime d'\''Amour'

  115. </pre></div>

  116. 

  117. </li><li> Include leading or trailing whitespaces using quoting:

  118. <div class="example">

  119. <pre class="example">'  this string starts and ends with whitespaces  '

  120. </pre></div>

  121. 

  122. </li><li> Escaping and quoting can be mixed together:

  123. <div class="example">

  124. <pre class="example">' The string '\'string\'' is a string '

  125. </pre></div>

  126. 

  127. </li><li> To include a literal &lsquo;<samp>\</samp>&rsquo; you can use either escaping or quoting:

  128. <div class="example">

  129. <pre class="example">'c:\foo' can be written as c:\\foo

  130. </pre></div>

  131. </li></ul>

  132. 

  133. <span id="date-syntax"></span><a name="Date"></a>

  134. <h3 class="section">2.2 Date<span class="pull-right"><a class="anchor hidden-xs" href="#Date" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Date" aria-hidden="true">TOC</a></span></h3>

  135. 

  136. <p>The accepted syntax is:

  137. </p><div class="example">

  138. <pre class="example">[(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...]]])|(HHMMSS[.m...]]]))[Z]

  139. now

  140. </pre></div>

  141. 

  142. <p>If the value is &quot;now&quot; it takes the current time.

  143. </p>

  144. <p>Time is local time unless Z is appended, in which case it is

  145. interpreted as UTC.

  146. If the year-month-day part is not specified it takes the current

  147. year-month-day.

  148. </p>

  149. <span id="time-duration-syntax"></span><a name="Time-duration"></a>

  150. <h3 class="section">2.3 Time duration<span class="pull-right"><a class="anchor hidden-xs" href="#Time-duration" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Time-duration" aria-hidden="true">TOC</a></span></h3>

  151. 

  152. <p>There are two accepted syntaxes for expressing time duration.

  153. </p>

  154. <div class="example">

  155. <pre class="example">[-][<var>HH</var>:]<var>MM</var>:<var>SS</var>[.<var>m</var>...]

  156. </pre></div>

  157. 

  158. <p><var>HH</var> expresses the number of hours, <var>MM</var> the number of minutes

  159. for a maximum of 2 digits, and <var>SS</var> the number of seconds for a

  160. maximum of 2 digits. The <var>m</var> at the end expresses decimal value for

  161. <var>SS</var>.

  162. </p>

  163. <p><em>or</em>

  164. </p>

  165. <div class="example">

  166. <pre class="example">[-]<var>S</var>+[.<var>m</var>...][s|ms|us]

  167. </pre></div>

  168. 

  169. <p><var>S</var> expresses the number of seconds, with the optional decimal part

  170. <var>m</var>.  The optional literal suffixes &lsquo;<samp>s</samp>&rsquo;, &lsquo;<samp>ms</samp>&rsquo; or &lsquo;<samp>us</samp>&rsquo;

  171. indicate to interpret the value as seconds, milliseconds or microseconds,

  172. respectively.

  173. </p>

  174. <p>In both expressions, the optional &lsquo;<samp>-</samp>&rsquo; indicates negative duration.

  175. </p>

  176. <a name="Examples-1"></a>

  177. <h4 class="subsection">2.3.1 Examples<span class="pull-right"><a class="anchor hidden-xs" href="#Examples-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Examples-1" aria-hidden="true">TOC</a></span></h4>

  178. 

  179. <p>The following examples are all valid time duration:

  180. </p>

  181. <dl compact="compact">

  182. <dt><span>&lsquo;<samp>55</samp>&rsquo;</span></dt>

  183. <dd><p>55 seconds

  184. </p>

  185. </dd>

  186. <dt><span>&lsquo;<samp>0.2</samp>&rsquo;</span></dt>

  187. <dd><p>0.2 seconds

  188. </p>

  189. </dd>

  190. <dt><span>&lsquo;<samp>200ms</samp>&rsquo;</span></dt>

  191. <dd><p>200 milliseconds, that&rsquo;s 0.2s

  192. </p>

  193. </dd>

  194. <dt><span>&lsquo;<samp>200000us</samp>&rsquo;</span></dt>

  195. <dd><p>200000 microseconds, that&rsquo;s 0.2s

  196. </p>

  197. </dd>

  198. <dt><span>&lsquo;<samp>12:03:45</samp>&rsquo;</span></dt>

  199. <dd><p>12 hours, 03 minutes and 45 seconds

  200. </p>

  201. </dd>

  202. <dt><span>&lsquo;<samp>23.189</samp>&rsquo;</span></dt>

  203. <dd><p>23.189 seconds

  204. </p></dd>

  205. </dl>

  206. 

  207. <span id="video-size-syntax"></span><a name="Video-size"></a>

  208. <h3 class="section">2.4 Video size<span class="pull-right"><a class="anchor hidden-xs" href="#Video-size" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Video-size" aria-hidden="true">TOC</a></span></h3>

  209. <p>Specify the size of the sourced video, it may be a string of the form

  210. <var>width</var>x<var>height</var>, or the name of a size abbreviation.

  211. </p>

  212. <p>The following abbreviations are recognized:

  213. </p><dl compact="compact">

  214. <dt><span>&lsquo;<samp>ntsc</samp>&rsquo;</span></dt>

  215. <dd><p>720x480

  216. </p></dd>

  217. <dt><span>&lsquo;<samp>pal</samp>&rsquo;</span></dt>

  218. <dd><p>720x576

  219. </p></dd>

  220. <dt><span>&lsquo;<samp>qntsc</samp>&rsquo;</span></dt>

  221. <dd><p>352x240

  222. </p></dd>

  223. <dt><span>&lsquo;<samp>qpal</samp>&rsquo;</span></dt>

  224. <dd><p>352x288

  225. </p></dd>

  226. <dt><span>&lsquo;<samp>sntsc</samp>&rsquo;</span></dt>

  227. <dd><p>640x480

  228. </p></dd>

  229. <dt><span>&lsquo;<samp>spal</samp>&rsquo;</span></dt>

  230. <dd><p>768x576

  231. </p></dd>

  232. <dt><span>&lsquo;<samp>film</samp>&rsquo;</span></dt>

  233. <dd><p>352x240

  234. </p></dd>

  235. <dt><span>&lsquo;<samp>ntsc-film</samp>&rsquo;</span></dt>

  236. <dd><p>352x240

  237. </p></dd>

  238. <dt><span>&lsquo;<samp>sqcif</samp>&rsquo;</span></dt>

  239. <dd><p>128x96

  240. </p></dd>

  241. <dt><span>&lsquo;<samp>qcif</samp>&rsquo;</span></dt>

  242. <dd><p>176x144

  243. </p></dd>

  244. <dt><span>&lsquo;<samp>cif</samp>&rsquo;</span></dt>

  245. <dd><p>352x288

  246. </p></dd>

  247. <dt><span>&lsquo;<samp>4cif</samp>&rsquo;</span></dt>

  248. <dd><p>704x576

  249. </p></dd>

  250. <dt><span>&lsquo;<samp>16cif</samp>&rsquo;</span></dt>

  251. <dd><p>1408x1152

  252. </p></dd>

  253. <dt><span>&lsquo;<samp>qqvga</samp>&rsquo;</span></dt>

  254. <dd><p>160x120

  255. </p></dd>

  256. <dt><span>&lsquo;<samp>qvga</samp>&rsquo;</span></dt>

  257. <dd><p>320x240

  258. </p></dd>

  259. <dt><span>&lsquo;<samp>vga</samp>&rsquo;</span></dt>

  260. <dd><p>640x480

  261. </p></dd>

  262. <dt><span>&lsquo;<samp>svga</samp>&rsquo;</span></dt>

  263. <dd><p>800x600

  264. </p></dd>

  265. <dt><span>&lsquo;<samp>xga</samp>&rsquo;</span></dt>

  266. <dd><p>1024x768

  267. </p></dd>

  268. <dt><span>&lsquo;<samp>uxga</samp>&rsquo;</span></dt>

  269. <dd><p>1600x1200

  270. </p></dd>

  271. <dt><span>&lsquo;<samp>qxga</samp>&rsquo;</span></dt>

  272. <dd><p>2048x1536

  273. </p></dd>

  274. <dt><span>&lsquo;<samp>sxga</samp>&rsquo;</span></dt>

  275. <dd><p>1280x1024

  276. </p></dd>

  277. <dt><span>&lsquo;<samp>qsxga</samp>&rsquo;</span></dt>

  278. <dd><p>2560x2048

  279. </p></dd>

  280. <dt><span>&lsquo;<samp>hsxga</samp>&rsquo;</span></dt>

  281. <dd><p>5120x4096

  282. </p></dd>

  283. <dt><span>&lsquo;<samp>wvga</samp>&rsquo;</span></dt>

  284. <dd><p>852x480

  285. </p></dd>

  286. <dt><span>&lsquo;<samp>wxga</samp>&rsquo;</span></dt>

  287. <dd><p>1366x768

  288. </p></dd>

  289. <dt><span>&lsquo;<samp>wsxga</samp>&rsquo;</span></dt>

  290. <dd><p>1600x1024

  291. </p></dd>

  292. <dt><span>&lsquo;<samp>wuxga</samp>&rsquo;</span></dt>

  293. <dd><p>1920x1200

  294. </p></dd>

  295. <dt><span>&lsquo;<samp>woxga</samp>&rsquo;</span></dt>

  296. <dd><p>2560x1600

  297. </p></dd>

  298. <dt><span>&lsquo;<samp>wqsxga</samp>&rsquo;</span></dt>

  299. <dd><p>3200x2048

  300. </p></dd>

  301. <dt><span>&lsquo;<samp>wquxga</samp>&rsquo;</span></dt>

  302. <dd><p>3840x2400

  303. </p></dd>

  304. <dt><span>&lsquo;<samp>whsxga</samp>&rsquo;</span></dt>

  305. <dd><p>6400x4096

  306. </p></dd>

  307. <dt><span>&lsquo;<samp>whuxga</samp>&rsquo;</span></dt>

  308. <dd><p>7680x4800

  309. </p></dd>

  310. <dt><span>&lsquo;<samp>cga</samp>&rsquo;</span></dt>

  311. <dd><p>320x200

  312. </p></dd>

  313. <dt><span>&lsquo;<samp>ega</samp>&rsquo;</span></dt>

  314. <dd><p>640x350

  315. </p></dd>

  316. <dt><span>&lsquo;<samp>hd480</samp>&rsquo;</span></dt>

  317. <dd><p>852x480

  318. </p></dd>

  319. <dt><span>&lsquo;<samp>hd720</samp>&rsquo;</span></dt>

  320. <dd><p>1280x720

  321. </p></dd>

  322. <dt><span>&lsquo;<samp>hd1080</samp>&rsquo;</span></dt>

  323. <dd><p>1920x1080

  324. </p></dd>

  325. <dt><span>&lsquo;<samp>2k</samp>&rsquo;</span></dt>

  326. <dd><p>2048x1080

  327. </p></dd>

  328. <dt><span>&lsquo;<samp>2kflat</samp>&rsquo;</span></dt>

  329. <dd><p>1998x1080

  330. </p></dd>

  331. <dt><span>&lsquo;<samp>2kscope</samp>&rsquo;</span></dt>

  332. <dd><p>2048x858

  333. </p></dd>

  334. <dt><span>&lsquo;<samp>4k</samp>&rsquo;</span></dt>

  335. <dd><p>4096x2160

  336. </p></dd>

  337. <dt><span>&lsquo;<samp>4kflat</samp>&rsquo;</span></dt>

  338. <dd><p>3996x2160

  339. </p></dd>

  340. <dt><span>&lsquo;<samp>4kscope</samp>&rsquo;</span></dt>

  341. <dd><p>4096x1716

  342. </p></dd>

  343. <dt><span>&lsquo;<samp>nhd</samp>&rsquo;</span></dt>

  344. <dd><p>640x360

  345. </p></dd>

  346. <dt><span>&lsquo;<samp>hqvga</samp>&rsquo;</span></dt>

  347. <dd><p>240x160

  348. </p></dd>

  349. <dt><span>&lsquo;<samp>wqvga</samp>&rsquo;</span></dt>

  350. <dd><p>400x240

  351. </p></dd>

  352. <dt><span>&lsquo;<samp>fwqvga</samp>&rsquo;</span></dt>

  353. <dd><p>432x240

  354. </p></dd>

  355. <dt><span>&lsquo;<samp>hvga</samp>&rsquo;</span></dt>

  356. <dd><p>480x320

  357. </p></dd>

  358. <dt><span>&lsquo;<samp>qhd</samp>&rsquo;</span></dt>

  359. <dd><p>960x540

  360. </p></dd>

  361. <dt><span>&lsquo;<samp>2kdci</samp>&rsquo;</span></dt>

  362. <dd><p>2048x1080

  363. </p></dd>

  364. <dt><span>&lsquo;<samp>4kdci</samp>&rsquo;</span></dt>

  365. <dd><p>4096x2160

  366. </p></dd>

  367. <dt><span>&lsquo;<samp>uhd2160</samp>&rsquo;</span></dt>

  368. <dd><p>3840x2160

  369. </p></dd>

  370. <dt><span>&lsquo;<samp>uhd4320</samp>&rsquo;</span></dt>

  371. <dd><p>7680x4320

  372. </p></dd>

  373. </dl>

  374. 

  375. <span id="video-rate-syntax"></span><a name="Video-rate"></a>

  376. <h3 class="section">2.5 Video rate<span class="pull-right"><a class="anchor hidden-xs" href="#Video-rate" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Video-rate" aria-hidden="true">TOC</a></span></h3>

  377. 

  378. <p>Specify the frame rate of a video, expressed as the number of frames

  379. generated per second. It has to be a string in the format

  380. <var>frame_rate_num</var>/<var>frame_rate_den</var>, an integer number, a float

  381. number or a valid video frame rate abbreviation.

  382. </p>

  383. <p>The following abbreviations are recognized:

  384. </p><dl compact="compact">

  385. <dt><span>&lsquo;<samp>ntsc</samp>&rsquo;</span></dt>

  386. <dd><p>30000/1001

  387. </p></dd>

  388. <dt><span>&lsquo;<samp>pal</samp>&rsquo;</span></dt>

  389. <dd><p>25/1

  390. </p></dd>

  391. <dt><span>&lsquo;<samp>qntsc</samp>&rsquo;</span></dt>

  392. <dd><p>30000/1001

  393. </p></dd>

  394. <dt><span>&lsquo;<samp>qpal</samp>&rsquo;</span></dt>

  395. <dd><p>25/1

  396. </p></dd>

  397. <dt><span>&lsquo;<samp>sntsc</samp>&rsquo;</span></dt>

  398. <dd><p>30000/1001

  399. </p></dd>

  400. <dt><span>&lsquo;<samp>spal</samp>&rsquo;</span></dt>

  401. <dd><p>25/1

  402. </p></dd>

  403. <dt><span>&lsquo;<samp>film</samp>&rsquo;</span></dt>

  404. <dd><p>24/1

  405. </p></dd>

  406. <dt><span>&lsquo;<samp>ntsc-film</samp>&rsquo;</span></dt>

  407. <dd><p>24000/1001

  408. </p></dd>

  409. </dl>

  410. 

  411. <span id="ratio-syntax"></span><a name="Ratio"></a>

  412. <h3 class="section">2.6 Ratio<span class="pull-right"><a class="anchor hidden-xs" href="#Ratio" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Ratio" aria-hidden="true">TOC</a></span></h3>

  413. 

  414. <p>A ratio can be expressed as an expression, or in the form

  415. <var>numerator</var>:<var>denominator</var>.

  416. </p>

  417. <p>Note that a ratio with infinite (1/0) or negative value is

  418. considered valid, so you should check on the returned value if you

  419. want to exclude those values.

  420. </p>

  421. <p>The undefined value can be expressed using the &quot;0:0&quot; string.

  422. </p>

  423. <span id="color-syntax"></span><a name="Color"></a>

  424. <h3 class="section">2.7 Color<span class="pull-right"><a class="anchor hidden-xs" href="#Color" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Color" aria-hidden="true">TOC</a></span></h3>

  425. 

  426. <p>It can be the name of a color as defined below (case insensitive match) or a

  427. <code>[0x|#]RRGGBB[AA]</code> sequence, possibly followed by @ and a string

  428. representing the alpha component.

  429. </p>

  430. <p>The alpha component may be a string composed by &quot;0x&quot; followed by an

  431. hexadecimal number or a decimal number between 0.0 and 1.0, which

  432. represents the opacity value (&lsquo;<samp>0x00</samp>&rsquo; or &lsquo;<samp>0.0</samp>&rsquo; means completely

  433. transparent, &lsquo;<samp>0xff</samp>&rsquo; or &lsquo;<samp>1.0</samp>&rsquo; completely opaque). If the alpha

  434. component is not specified then &lsquo;<samp>0xff</samp>&rsquo; is assumed.

  435. </p>

  436. <p>The string &lsquo;<samp>random</samp>&rsquo; will result in a random color.

  437. </p>

  438. <p>The following names of colors are recognized:

  439. </p><dl compact="compact">

  440. <dt><span>&lsquo;<samp>AliceBlue</samp>&rsquo;</span></dt>

  441. <dd><p>0xF0F8FF

  442. </p></dd>

  443. <dt><span>&lsquo;<samp>AntiqueWhite</samp>&rsquo;</span></dt>

  444. <dd><p>0xFAEBD7

  445. </p></dd>

  446. <dt><span>&lsquo;<samp>Aqua</samp>&rsquo;</span></dt>

  447. <dd><p>0x00FFFF

  448. </p></dd>

  449. <dt><span>&lsquo;<samp>Aquamarine</samp>&rsquo;</span></dt>

  450. <dd><p>0x7FFFD4

  451. </p></dd>

  452. <dt><span>&lsquo;<samp>Azure</samp>&rsquo;</span></dt>

  453. <dd><p>0xF0FFFF

  454. </p></dd>

  455. <dt><span>&lsquo;<samp>Beige</samp>&rsquo;</span></dt>

  456. <dd><p>0xF5F5DC

  457. </p></dd>

  458. <dt><span>&lsquo;<samp>Bisque</samp>&rsquo;</span></dt>

  459. <dd><p>0xFFE4C4

  460. </p></dd>

  461. <dt><span>&lsquo;<samp>Black</samp>&rsquo;</span></dt>

  462. <dd><p>0x000000

  463. </p></dd>

  464. <dt><span>&lsquo;<samp>BlanchedAlmond</samp>&rsquo;</span></dt>

  465. <dd><p>0xFFEBCD

  466. </p></dd>

  467. <dt><span>&lsquo;<samp>Blue</samp>&rsquo;</span></dt>

  468. <dd><p>0x0000FF

  469. </p></dd>

  470. <dt><span>&lsquo;<samp>BlueViolet</samp>&rsquo;</span></dt>

  471. <dd><p>0x8A2BE2

  472. </p></dd>

  473. <dt><span>&lsquo;<samp>Brown</samp>&rsquo;</span></dt>

  474. <dd><p>0xA52A2A

  475. </p></dd>

  476. <dt><span>&lsquo;<samp>BurlyWood</samp>&rsquo;</span></dt>

  477. <dd><p>0xDEB887

  478. </p></dd>

  479. <dt><span>&lsquo;<samp>CadetBlue</samp>&rsquo;</span></dt>

  480. <dd><p>0x5F9EA0

  481. </p></dd>

  482. <dt><span>&lsquo;<samp>Chartreuse</samp>&rsquo;</span></dt>

  483. <dd><p>0x7FFF00

  484. </p></dd>

  485. <dt><span>&lsquo;<samp>Chocolate</samp>&rsquo;</span></dt>

  486. <dd><p>0xD2691E

  487. </p></dd>

  488. <dt><span>&lsquo;<samp>Coral</samp>&rsquo;</span></dt>

  489. <dd><p>0xFF7F50

  490. </p></dd>

  491. <dt><span>&lsquo;<samp>CornflowerBlue</samp>&rsquo;</span></dt>

  492. <dd><p>0x6495ED

  493. </p></dd>

  494. <dt><span>&lsquo;<samp>Cornsilk</samp>&rsquo;</span></dt>

  495. <dd><p>0xFFF8DC

  496. </p></dd>

  497. <dt><span>&lsquo;<samp>Crimson</samp>&rsquo;</span></dt>

  498. <dd><p>0xDC143C

  499. </p></dd>

  500. <dt><span>&lsquo;<samp>Cyan</samp>&rsquo;</span></dt>

  501. <dd><p>0x00FFFF

  502. </p></dd>

  503. <dt><span>&lsquo;<samp>DarkBlue</samp>&rsquo;</span></dt>

  504. <dd><p>0x00008B

  505. </p></dd>

  506. <dt><span>&lsquo;<samp>DarkCyan</samp>&rsquo;</span></dt>

  507. <dd><p>0x008B8B

  508. </p></dd>

  509. <dt><span>&lsquo;<samp>DarkGoldenRod</samp>&rsquo;</span></dt>

  510. <dd><p>0xB8860B

  511. </p></dd>

  512. <dt><span>&lsquo;<samp>DarkGray</samp>&rsquo;</span></dt>

  513. <dd><p>0xA9A9A9

  514. </p></dd>

  515. <dt><span>&lsquo;<samp>DarkGreen</samp>&rsquo;</span></dt>

  516. <dd><p>0x006400

  517. </p></dd>

  518. <dt><span>&lsquo;<samp>DarkKhaki</samp>&rsquo;</span></dt>

  519. <dd><p>0xBDB76B

  520. </p></dd>

  521. <dt><span>&lsquo;<samp>DarkMagenta</samp>&rsquo;</span></dt>

  522. <dd><p>0x8B008B

  523. </p></dd>

  524. <dt><span>&lsquo;<samp>DarkOliveGreen</samp>&rsquo;</span></dt>

  525. <dd><p>0x556B2F

  526. </p></dd>

  527. <dt><span>&lsquo;<samp>Darkorange</samp>&rsquo;</span></dt>

  528. <dd><p>0xFF8C00

  529. </p></dd>

  530. <dt><span>&lsquo;<samp>DarkOrchid</samp>&rsquo;</span></dt>

  531. <dd><p>0x9932CC

  532. </p></dd>

  533. <dt><span>&lsquo;<samp>DarkRed</samp>&rsquo;</span></dt>

  534. <dd><p>0x8B0000

  535. </p></dd>

  536. <dt><span>&lsquo;<samp>DarkSalmon</samp>&rsquo;</span></dt>

  537. <dd><p>0xE9967A

  538. </p></dd>

  539. <dt><span>&lsquo;<samp>DarkSeaGreen</samp>&rsquo;</span></dt>

  540. <dd><p>0x8FBC8F

  541. </p></dd>

  542. <dt><span>&lsquo;<samp>DarkSlateBlue</samp>&rsquo;</span></dt>

  543. <dd><p>0x483D8B

  544. </p></dd>

  545. <dt><span>&lsquo;<samp>DarkSlateGray</samp>&rsquo;</span></dt>

  546. <dd><p>0x2F4F4F

  547. </p></dd>

  548. <dt><span>&lsquo;<samp>DarkTurquoise</samp>&rsquo;</span></dt>

  549. <dd><p>0x00CED1

  550. </p></dd>

  551. <dt><span>&lsquo;<samp>DarkViolet</samp>&rsquo;</span></dt>

  552. <dd><p>0x9400D3

  553. </p></dd>

  554. <dt><span>&lsquo;<samp>DeepPink</samp>&rsquo;</span></dt>

  555. <dd><p>0xFF1493

  556. </p></dd>

  557. <dt><span>&lsquo;<samp>DeepSkyBlue</samp>&rsquo;</span></dt>

  558. <dd><p>0x00BFFF

  559. </p></dd>

  560. <dt><span>&lsquo;<samp>DimGray</samp>&rsquo;</span></dt>

  561. <dd><p>0x696969

  562. </p></dd>

  563. <dt><span>&lsquo;<samp>DodgerBlue</samp>&rsquo;</span></dt>

  564. <dd><p>0x1E90FF

  565. </p></dd>

  566. <dt><span>&lsquo;<samp>FireBrick</samp>&rsquo;</span></dt>

  567. <dd><p>0xB22222

  568. </p></dd>

  569. <dt><span>&lsquo;<samp>FloralWhite</samp>&rsquo;</span></dt>

  570. <dd><p>0xFFFAF0

  571. </p></dd>

  572. <dt><span>&lsquo;<samp>ForestGreen</samp>&rsquo;</span></dt>

  573. <dd><p>0x228B22

  574. </p></dd>

  575. <dt><span>&lsquo;<samp>Fuchsia</samp>&rsquo;</span></dt>

  576. <dd><p>0xFF00FF

  577. </p></dd>

  578. <dt><span>&lsquo;<samp>Gainsboro</samp>&rsquo;</span></dt>

  579. <dd><p>0xDCDCDC

  580. </p></dd>

  581. <dt><span>&lsquo;<samp>GhostWhite</samp>&rsquo;</span></dt>

  582. <dd><p>0xF8F8FF

  583. </p></dd>

  584. <dt><span>&lsquo;<samp>Gold</samp>&rsquo;</span></dt>

  585. <dd><p>0xFFD700

  586. </p></dd>

  587. <dt><span>&lsquo;<samp>GoldenRod</samp>&rsquo;</span></dt>

  588. <dd><p>0xDAA520

  589. </p></dd>

  590. <dt><span>&lsquo;<samp>Gray</samp>&rsquo;</span></dt>

  591. <dd><p>0x808080

  592. </p></dd>

  593. <dt><span>&lsquo;<samp>Green</samp>&rsquo;</span></dt>

  594. <dd><p>0x008000

  595. </p></dd>

  596. <dt><span>&lsquo;<samp>GreenYellow</samp>&rsquo;</span></dt>

  597. <dd><p>0xADFF2F

  598. </p></dd>

  599. <dt><span>&lsquo;<samp>HoneyDew</samp>&rsquo;</span></dt>

  600. <dd><p>0xF0FFF0

  601. </p></dd>

  602. <dt><span>&lsquo;<samp>HotPink</samp>&rsquo;</span></dt>

  603. <dd><p>0xFF69B4

  604. </p></dd>

  605. <dt><span>&lsquo;<samp>IndianRed</samp>&rsquo;</span></dt>

  606. <dd><p>0xCD5C5C

  607. </p></dd>

  608. <dt><span>&lsquo;<samp>Indigo</samp>&rsquo;</span></dt>

  609. <dd><p>0x4B0082

  610. </p></dd>

  611. <dt><span>&lsquo;<samp>Ivory</samp>&rsquo;</span></dt>

  612. <dd><p>0xFFFFF0

  613. </p></dd>

  614. <dt><span>&lsquo;<samp>Khaki</samp>&rsquo;</span></dt>

  615. <dd><p>0xF0E68C

  616. </p></dd>

  617. <dt><span>&lsquo;<samp>Lavender</samp>&rsquo;</span></dt>

  618. <dd><p>0xE6E6FA

  619. </p></dd>

  620. <dt><span>&lsquo;<samp>LavenderBlush</samp>&rsquo;</span></dt>

  621. <dd><p>0xFFF0F5

  622. </p></dd>

  623. <dt><span>&lsquo;<samp>LawnGreen</samp>&rsquo;</span></dt>

  624. <dd><p>0x7CFC00

  625. </p></dd>

  626. <dt><span>&lsquo;<samp>LemonChiffon</samp>&rsquo;</span></dt>

  627. <dd><p>0xFFFACD

  628. </p></dd>

  629. <dt><span>&lsquo;<samp>LightBlue</samp>&rsquo;</span></dt>

  630. <dd><p>0xADD8E6

  631. </p></dd>

  632. <dt><span>&lsquo;<samp>LightCoral</samp>&rsquo;</span></dt>

  633. <dd><p>0xF08080

  634. </p></dd>

  635. <dt><span>&lsquo;<samp>LightCyan</samp>&rsquo;</span></dt>

  636. <dd><p>0xE0FFFF

  637. </p></dd>

  638. <dt><span>&lsquo;<samp>LightGoldenRodYellow</samp>&rsquo;</span></dt>

  639. <dd><p>0xFAFAD2

  640. </p></dd>

  641. <dt><span>&lsquo;<samp>LightGreen</samp>&rsquo;</span></dt>

  642. <dd><p>0x90EE90

  643. </p></dd>

  644. <dt><span>&lsquo;<samp>LightGrey</samp>&rsquo;</span></dt>

  645. <dd><p>0xD3D3D3

  646. </p></dd>

  647. <dt><span>&lsquo;<samp>LightPink</samp>&rsquo;</span></dt>

  648. <dd><p>0xFFB6C1

  649. </p></dd>

  650. <dt><span>&lsquo;<samp>LightSalmon</samp>&rsquo;</span></dt>

  651. <dd><p>0xFFA07A

  652. </p></dd>

  653. <dt><span>&lsquo;<samp>LightSeaGreen</samp>&rsquo;</span></dt>

  654. <dd><p>0x20B2AA

  655. </p></dd>

  656. <dt><span>&lsquo;<samp>LightSkyBlue</samp>&rsquo;</span></dt>

  657. <dd><p>0x87CEFA

  658. </p></dd>

  659. <dt><span>&lsquo;<samp>LightSlateGray</samp>&rsquo;</span></dt>

  660. <dd><p>0x778899

  661. </p></dd>

  662. <dt><span>&lsquo;<samp>LightSteelBlue</samp>&rsquo;</span></dt>

  663. <dd><p>0xB0C4DE

  664. </p></dd>

  665. <dt><span>&lsquo;<samp>LightYellow</samp>&rsquo;</span></dt>

  666. <dd><p>0xFFFFE0

  667. </p></dd>

  668. <dt><span>&lsquo;<samp>Lime</samp>&rsquo;</span></dt>

  669. <dd><p>0x00FF00

  670. </p></dd>

  671. <dt><span>&lsquo;<samp>LimeGreen</samp>&rsquo;</span></dt>

  672. <dd><p>0x32CD32

  673. </p></dd>

  674. <dt><span>&lsquo;<samp>Linen</samp>&rsquo;</span></dt>

  675. <dd><p>0xFAF0E6

  676. </p></dd>

  677. <dt><span>&lsquo;<samp>Magenta</samp>&rsquo;</span></dt>

  678. <dd><p>0xFF00FF

  679. </p></dd>

  680. <dt><span>&lsquo;<samp>Maroon</samp>&rsquo;</span></dt>

  681. <dd><p>0x800000

  682. </p></dd>

  683. <dt><span>&lsquo;<samp>MediumAquaMarine</samp>&rsquo;</span></dt>

  684. <dd><p>0x66CDAA

  685. </p></dd>

  686. <dt><span>&lsquo;<samp>MediumBlue</samp>&rsquo;</span></dt>

  687. <dd><p>0x0000CD

  688. </p></dd>

  689. <dt><span>&lsquo;<samp>MediumOrchid</samp>&rsquo;</span></dt>

  690. <dd><p>0xBA55D3

  691. </p></dd>

  692. <dt><span>&lsquo;<samp>MediumPurple</samp>&rsquo;</span></dt>

  693. <dd><p>0x9370D8

  694. </p></dd>

  695. <dt><span>&lsquo;<samp>MediumSeaGreen</samp>&rsquo;</span></dt>

  696. <dd><p>0x3CB371

  697. </p></dd>

  698. <dt><span>&lsquo;<samp>MediumSlateBlue</samp>&rsquo;</span></dt>

  699. <dd><p>0x7B68EE

  700. </p></dd>

  701. <dt><span>&lsquo;<samp>MediumSpringGreen</samp>&rsquo;</span></dt>

  702. <dd><p>0x00FA9A

  703. </p></dd>

  704. <dt><span>&lsquo;<samp>MediumTurquoise</samp>&rsquo;</span></dt>

  705. <dd><p>0x48D1CC

  706. </p></dd>

  707. <dt><span>&lsquo;<samp>MediumVioletRed</samp>&rsquo;</span></dt>

  708. <dd><p>0xC71585

  709. </p></dd>

  710. <dt><span>&lsquo;<samp>MidnightBlue</samp>&rsquo;</span></dt>

  711. <dd><p>0x191970

  712. </p></dd>

  713. <dt><span>&lsquo;<samp>MintCream</samp>&rsquo;</span></dt>

  714. <dd><p>0xF5FFFA

  715. </p></dd>

  716. <dt><span>&lsquo;<samp>MistyRose</samp>&rsquo;</span></dt>

  717. <dd><p>0xFFE4E1

  718. </p></dd>

  719. <dt><span>&lsquo;<samp>Moccasin</samp>&rsquo;</span></dt>

  720. <dd><p>0xFFE4B5

  721. </p></dd>

  722. <dt><span>&lsquo;<samp>NavajoWhite</samp>&rsquo;</span></dt>

  723. <dd><p>0xFFDEAD

  724. </p></dd>

  725. <dt><span>&lsquo;<samp>Navy</samp>&rsquo;</span></dt>

  726. <dd><p>0x000080

  727. </p></dd>

  728. <dt><span>&lsquo;<samp>OldLace</samp>&rsquo;</span></dt>

  729. <dd><p>0xFDF5E6

  730. </p></dd>

  731. <dt><span>&lsquo;<samp>Olive</samp>&rsquo;</span></dt>

  732. <dd><p>0x808000

  733. </p></dd>

  734. <dt><span>&lsquo;<samp>OliveDrab</samp>&rsquo;</span></dt>

  735. <dd><p>0x6B8E23

  736. </p></dd>

  737. <dt><span>&lsquo;<samp>Orange</samp>&rsquo;</span></dt>

  738. <dd><p>0xFFA500

  739. </p></dd>

  740. <dt><span>&lsquo;<samp>OrangeRed</samp>&rsquo;</span></dt>

  741. <dd><p>0xFF4500

  742. </p></dd>

  743. <dt><span>&lsquo;<samp>Orchid</samp>&rsquo;</span></dt>

  744. <dd><p>0xDA70D6

  745. </p></dd>

  746. <dt><span>&lsquo;<samp>PaleGoldenRod</samp>&rsquo;</span></dt>

  747. <dd><p>0xEEE8AA

  748. </p></dd>

  749. <dt><span>&lsquo;<samp>PaleGreen</samp>&rsquo;</span></dt>

  750. <dd><p>0x98FB98

  751. </p></dd>

  752. <dt><span>&lsquo;<samp>PaleTurquoise</samp>&rsquo;</span></dt>

  753. <dd><p>0xAFEEEE

  754. </p></dd>

  755. <dt><span>&lsquo;<samp>PaleVioletRed</samp>&rsquo;</span></dt>

  756. <dd><p>0xD87093

  757. </p></dd>

  758. <dt><span>&lsquo;<samp>PapayaWhip</samp>&rsquo;</span></dt>

  759. <dd><p>0xFFEFD5

  760. </p></dd>

  761. <dt><span>&lsquo;<samp>PeachPuff</samp>&rsquo;</span></dt>

  762. <dd><p>0xFFDAB9

  763. </p></dd>

  764. <dt><span>&lsquo;<samp>Peru</samp>&rsquo;</span></dt>

  765. <dd><p>0xCD853F

  766. </p></dd>

  767. <dt><span>&lsquo;<samp>Pink</samp>&rsquo;</span></dt>

  768. <dd><p>0xFFC0CB

  769. </p></dd>

  770. <dt><span>&lsquo;<samp>Plum</samp>&rsquo;</span></dt>

  771. <dd><p>0xDDA0DD

  772. </p></dd>

  773. <dt><span>&lsquo;<samp>PowderBlue</samp>&rsquo;</span></dt>

  774. <dd><p>0xB0E0E6

  775. </p></dd>

  776. <dt><span>&lsquo;<samp>Purple</samp>&rsquo;</span></dt>

  777. <dd><p>0x800080

  778. </p></dd>

  779. <dt><span>&lsquo;<samp>Red</samp>&rsquo;</span></dt>

  780. <dd><p>0xFF0000

  781. </p></dd>

  782. <dt><span>&lsquo;<samp>RosyBrown</samp>&rsquo;</span></dt>

  783. <dd><p>0xBC8F8F

  784. </p></dd>

  785. <dt><span>&lsquo;<samp>RoyalBlue</samp>&rsquo;</span></dt>

  786. <dd><p>0x4169E1

  787. </p></dd>

  788. <dt><span>&lsquo;<samp>SaddleBrown</samp>&rsquo;</span></dt>

  789. <dd><p>0x8B4513

  790. </p></dd>

  791. <dt><span>&lsquo;<samp>Salmon</samp>&rsquo;</span></dt>

  792. <dd><p>0xFA8072

  793. </p></dd>

  794. <dt><span>&lsquo;<samp>SandyBrown</samp>&rsquo;</span></dt>

  795. <dd><p>0xF4A460

  796. </p></dd>

  797. <dt><span>&lsquo;<samp>SeaGreen</samp>&rsquo;</span></dt>

  798. <dd><p>0x2E8B57

  799. </p></dd>

  800. <dt><span>&lsquo;<samp>SeaShell</samp>&rsquo;</span></dt>

  801. <dd><p>0xFFF5EE

  802. </p></dd>

  803. <dt><span>&lsquo;<samp>Sienna</samp>&rsquo;</span></dt>

  804. <dd><p>0xA0522D

  805. </p></dd>

  806. <dt><span>&lsquo;<samp>Silver</samp>&rsquo;</span></dt>

  807. <dd><p>0xC0C0C0

  808. </p></dd>

  809. <dt><span>&lsquo;<samp>SkyBlue</samp>&rsquo;</span></dt>

  810. <dd><p>0x87CEEB

  811. </p></dd>

  812. <dt><span>&lsquo;<samp>SlateBlue</samp>&rsquo;</span></dt>

  813. <dd><p>0x6A5ACD

  814. </p></dd>

  815. <dt><span>&lsquo;<samp>SlateGray</samp>&rsquo;</span></dt>

  816. <dd><p>0x708090

  817. </p></dd>

  818. <dt><span>&lsquo;<samp>Snow</samp>&rsquo;</span></dt>

  819. <dd><p>0xFFFAFA

  820. </p></dd>

  821. <dt><span>&lsquo;<samp>SpringGreen</samp>&rsquo;</span></dt>

  822. <dd><p>0x00FF7F

  823. </p></dd>

  824. <dt><span>&lsquo;<samp>SteelBlue</samp>&rsquo;</span></dt>

  825. <dd><p>0x4682B4

  826. </p></dd>

  827. <dt><span>&lsquo;<samp>Tan</samp>&rsquo;</span></dt>

  828. <dd><p>0xD2B48C

  829. </p></dd>

  830. <dt><span>&lsquo;<samp>Teal</samp>&rsquo;</span></dt>

  831. <dd><p>0x008080

  832. </p></dd>

  833. <dt><span>&lsquo;<samp>Thistle</samp>&rsquo;</span></dt>

  834. <dd><p>0xD8BFD8

  835. </p></dd>

  836. <dt><span>&lsquo;<samp>Tomato</samp>&rsquo;</span></dt>

  837. <dd><p>0xFF6347

  838. </p></dd>

  839. <dt><span>&lsquo;<samp>Turquoise</samp>&rsquo;</span></dt>

  840. <dd><p>0x40E0D0

  841. </p></dd>

  842. <dt><span>&lsquo;<samp>Violet</samp>&rsquo;</span></dt>

  843. <dd><p>0xEE82EE

  844. </p></dd>

  845. <dt><span>&lsquo;<samp>Wheat</samp>&rsquo;</span></dt>

  846. <dd><p>0xF5DEB3

  847. </p></dd>

  848. <dt><span>&lsquo;<samp>White</samp>&rsquo;</span></dt>

  849. <dd><p>0xFFFFFF

  850. </p></dd>

  851. <dt><span>&lsquo;<samp>WhiteSmoke</samp>&rsquo;</span></dt>

  852. <dd><p>0xF5F5F5

  853. </p></dd>

  854. <dt><span>&lsquo;<samp>Yellow</samp>&rsquo;</span></dt>

  855. <dd><p>0xFFFF00

  856. </p></dd>

  857. <dt><span>&lsquo;<samp>YellowGreen</samp>&rsquo;</span></dt>

  858. <dd><p>0x9ACD32

  859. </p></dd>

  860. </dl>

  861. 

  862. <span id="channel-layout-syntax"></span><a name="Channel-Layout"></a>

  863. <h3 class="section">2.8 Channel Layout<span class="pull-right"><a class="anchor hidden-xs" href="#Channel-Layout" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Channel-Layout" aria-hidden="true">TOC</a></span></h3>

  864. 

  865. <p>A channel layout specifies the spatial disposition of the channels in

  866. a multi-channel audio stream. To specify a channel layout, FFmpeg

  867. makes use of a special syntax.

  868. </p>

  869. <p>Individual channels are identified by an id, as given by the table

  870. below:

  871. </p><dl compact="compact">

  872. <dt><span>&lsquo;<samp>FL</samp>&rsquo;</span></dt>

  873. <dd><p>front left

  874. </p></dd>

  875. <dt><span>&lsquo;<samp>FR</samp>&rsquo;</span></dt>

  876. <dd><p>front right

  877. </p></dd>

  878. <dt><span>&lsquo;<samp>FC</samp>&rsquo;</span></dt>

  879. <dd><p>front center

  880. </p></dd>

  881. <dt><span>&lsquo;<samp>LFE</samp>&rsquo;</span></dt>

  882. <dd><p>low frequency

  883. </p></dd>

  884. <dt><span>&lsquo;<samp>BL</samp>&rsquo;</span></dt>

  885. <dd><p>back left

  886. </p></dd>

  887. <dt><span>&lsquo;<samp>BR</samp>&rsquo;</span></dt>

  888. <dd><p>back right

  889. </p></dd>

  890. <dt><span>&lsquo;<samp>FLC</samp>&rsquo;</span></dt>

  891. <dd><p>front left-of-center

  892. </p></dd>

  893. <dt><span>&lsquo;<samp>FRC</samp>&rsquo;</span></dt>

  894. <dd><p>front right-of-center

  895. </p></dd>

  896. <dt><span>&lsquo;<samp>BC</samp>&rsquo;</span></dt>

  897. <dd><p>back center

  898. </p></dd>

  899. <dt><span>&lsquo;<samp>SL</samp>&rsquo;</span></dt>

  900. <dd><p>side left

  901. </p></dd>

  902. <dt><span>&lsquo;<samp>SR</samp>&rsquo;</span></dt>

  903. <dd><p>side right

  904. </p></dd>

  905. <dt><span>&lsquo;<samp>TC</samp>&rsquo;</span></dt>

  906. <dd><p>top center

  907. </p></dd>

  908. <dt><span>&lsquo;<samp>TFL</samp>&rsquo;</span></dt>

  909. <dd><p>top front left

  910. </p></dd>

  911. <dt><span>&lsquo;<samp>TFC</samp>&rsquo;</span></dt>

  912. <dd><p>top front center

  913. </p></dd>

  914. <dt><span>&lsquo;<samp>TFR</samp>&rsquo;</span></dt>

  915. <dd><p>top front right

  916. </p></dd>

  917. <dt><span>&lsquo;<samp>TBL</samp>&rsquo;</span></dt>

  918. <dd><p>top back left

  919. </p></dd>

  920. <dt><span>&lsquo;<samp>TBC</samp>&rsquo;</span></dt>

  921. <dd><p>top back center

  922. </p></dd>

  923. <dt><span>&lsquo;<samp>TBR</samp>&rsquo;</span></dt>

  924. <dd><p>top back right

  925. </p></dd>

  926. <dt><span>&lsquo;<samp>DL</samp>&rsquo;</span></dt>

  927. <dd><p>downmix left

  928. </p></dd>

  929. <dt><span>&lsquo;<samp>DR</samp>&rsquo;</span></dt>

  930. <dd><p>downmix right

  931. </p></dd>

  932. <dt><span>&lsquo;<samp>WL</samp>&rsquo;</span></dt>

  933. <dd><p>wide left

  934. </p></dd>

  935. <dt><span>&lsquo;<samp>WR</samp>&rsquo;</span></dt>

  936. <dd><p>wide right

  937. </p></dd>

  938. <dt><span>&lsquo;<samp>SDL</samp>&rsquo;</span></dt>

  939. <dd><p>surround direct left

  940. </p></dd>

  941. <dt><span>&lsquo;<samp>SDR</samp>&rsquo;</span></dt>

  942. <dd><p>surround direct right

  943. </p></dd>

  944. <dt><span>&lsquo;<samp>LFE2</samp>&rsquo;</span></dt>

  945. <dd><p>low frequency 2

  946. </p></dd>

  947. </dl>

  948. 

  949. <p>Standard channel layout compositions can be specified by using the

  950. following identifiers:

  951. </p><dl compact="compact">

  952. <dt><span>&lsquo;<samp>mono</samp>&rsquo;</span></dt>

  953. <dd><p>FC

  954. </p></dd>

  955. <dt><span>&lsquo;<samp>stereo</samp>&rsquo;</span></dt>

  956. <dd><p>FL+FR

  957. </p></dd>

  958. <dt><span>&lsquo;<samp>2.1</samp>&rsquo;</span></dt>

  959. <dd><p>FL+FR+LFE

  960. </p></dd>

  961. <dt><span>&lsquo;<samp>3.0</samp>&rsquo;</span></dt>

  962. <dd><p>FL+FR+FC

  963. </p></dd>

  964. <dt><span>&lsquo;<samp>3.0(back)</samp>&rsquo;</span></dt>

  965. <dd><p>FL+FR+BC

  966. </p></dd>

  967. <dt><span>&lsquo;<samp>4.0</samp>&rsquo;</span></dt>

  968. <dd><p>FL+FR+FC+BC

  969. </p></dd>

  970. <dt><span>&lsquo;<samp>quad</samp>&rsquo;</span></dt>

  971. <dd><p>FL+FR+BL+BR

  972. </p></dd>

  973. <dt><span>&lsquo;<samp>quad(side)</samp>&rsquo;</span></dt>

  974. <dd><p>FL+FR+SL+SR

  975. </p></dd>

  976. <dt><span>&lsquo;<samp>3.1</samp>&rsquo;</span></dt>

  977. <dd><p>FL+FR+FC+LFE

  978. </p></dd>

  979. <dt><span>&lsquo;<samp>5.0</samp>&rsquo;</span></dt>

  980. <dd><p>FL+FR+FC+BL+BR

  981. </p></dd>

  982. <dt><span>&lsquo;<samp>5.0(side)</samp>&rsquo;</span></dt>

  983. <dd><p>FL+FR+FC+SL+SR

  984. </p></dd>

  985. <dt><span>&lsquo;<samp>4.1</samp>&rsquo;</span></dt>

  986. <dd><p>FL+FR+FC+LFE+BC

  987. </p></dd>

  988. <dt><span>&lsquo;<samp>5.1</samp>&rsquo;</span></dt>

  989. <dd><p>FL+FR+FC+LFE+BL+BR

  990. </p></dd>

  991. <dt><span>&lsquo;<samp>5.1(side)</samp>&rsquo;</span></dt>

  992. <dd><p>FL+FR+FC+LFE+SL+SR

  993. </p></dd>

  994. <dt><span>&lsquo;<samp>6.0</samp>&rsquo;</span></dt>

  995. <dd><p>FL+FR+FC+BC+SL+SR

  996. </p></dd>

  997. <dt><span>&lsquo;<samp>6.0(front)</samp>&rsquo;</span></dt>

  998. <dd><p>FL+FR+FLC+FRC+SL+SR

  999. </p></dd>

  1000. <dt><span>&lsquo;<samp>hexagonal</samp>&rsquo;</span></dt>

  1001. <dd><p>FL+FR+FC+BL+BR+BC

  1002. </p></dd>

  1003. <dt><span>&lsquo;<samp>6.1</samp>&rsquo;</span></dt>

  1004. <dd><p>FL+FR+FC+LFE+BC+SL+SR

  1005. </p></dd>

  1006. <dt><span>&lsquo;<samp>6.1</samp>&rsquo;</span></dt>

  1007. <dd><p>FL+FR+FC+LFE+BL+BR+BC

  1008. </p></dd>

  1009. <dt><span>&lsquo;<samp>6.1(front)</samp>&rsquo;</span></dt>

  1010. <dd><p>FL+FR+LFE+FLC+FRC+SL+SR

  1011. </p></dd>

  1012. <dt><span>&lsquo;<samp>7.0</samp>&rsquo;</span></dt>

  1013. <dd><p>FL+FR+FC+BL+BR+SL+SR

  1014. </p></dd>

  1015. <dt><span>&lsquo;<samp>7.0(front)</samp>&rsquo;</span></dt>

  1016. <dd><p>FL+FR+FC+FLC+FRC+SL+SR

  1017. </p></dd>

  1018. <dt><span>&lsquo;<samp>7.1</samp>&rsquo;</span></dt>

  1019. <dd><p>FL+FR+FC+LFE+BL+BR+SL+SR

  1020. </p></dd>

  1021. <dt><span>&lsquo;<samp>7.1(wide)</samp>&rsquo;</span></dt>

  1022. <dd><p>FL+FR+FC+LFE+BL+BR+FLC+FRC

  1023. </p></dd>

  1024. <dt><span>&lsquo;<samp>7.1(wide-side)</samp>&rsquo;</span></dt>

  1025. <dd><p>FL+FR+FC+LFE+FLC+FRC+SL+SR

  1026. </p></dd>

  1027. <dt><span>&lsquo;<samp>7.1(top)</samp>&rsquo;</span></dt>

  1028. <dd><p>FL+FR+FC+LFE+BL+BR+TFL+TFR

  1029. </p></dd>

  1030. <dt><span>&lsquo;<samp>octagonal</samp>&rsquo;</span></dt>

  1031. <dd><p>FL+FR+FC+BL+BR+BC+SL+SR

  1032. </p></dd>

  1033. <dt><span>&lsquo;<samp>cube</samp>&rsquo;</span></dt>

  1034. <dd><p>FL+FR+BL+BR+TFL+TFR+TBL+TBR

  1035. </p></dd>

  1036. <dt><span>&lsquo;<samp>hexadecagonal</samp>&rsquo;</span></dt>

  1037. <dd><p>FL+FR+FC+BL+BR+BC+SL+SR+WL+WR+TBL+TBR+TBC+TFC+TFL+TFR

  1038. </p></dd>

  1039. <dt><span>&lsquo;<samp>downmix</samp>&rsquo;</span></dt>

  1040. <dd><p>DL+DR

  1041. </p></dd>

  1042. <dt><span>&lsquo;<samp>22.2</samp>&rsquo;</span></dt>

  1043. <dd><p>FL+FR+FC+LFE+BL+BR+FLC+FRC+BC+SL+SR+TC+TFL+TFC+TFR+TBL+TBC+TBR+LFE2+TSL+TSR+BFC+BFL+BFR

  1044. </p></dd>

  1045. </dl>

  1046. 

  1047. <p>A custom channel layout can be specified as a sequence of terms, separated by &rsquo;+&rsquo;.

  1048. Each term can be:

  1049. </p><ul>

  1050. <li> the name of a single channel (e.g. &lsquo;<samp>FL</samp>&rsquo;, &lsquo;<samp>FR</samp>&rsquo;, &lsquo;<samp>FC</samp>&rsquo;, &lsquo;<samp>LFE</samp>&rsquo;, etc.),

  1051. each optionally containing a custom name after a &rsquo;@&rsquo;, (e.g. &lsquo;<samp>FL@Left</samp>&rsquo;,

  1052. &lsquo;<samp>FR@Right</samp>&rsquo;, &lsquo;<samp>FC@Center</samp>&rsquo;, &lsquo;<samp>LFE@Low_Frequency</samp>&rsquo;, etc.)

  1053. </li></ul>

  1054. 

  1055. <p>A standard channel layout can be specified by the following:

  1056. </p><ul>

  1057. <li> the name of a single channel (e.g. &lsquo;<samp>FL</samp>&rsquo;, &lsquo;<samp>FR</samp>&rsquo;, &lsquo;<samp>FC</samp>&rsquo;, &lsquo;<samp>LFE</samp>&rsquo;, etc.)

  1058. 

  1059. </li><li> the name of a standard channel layout (e.g. &lsquo;<samp>mono</samp>&rsquo;,

  1060. &lsquo;<samp>stereo</samp>&rsquo;, &lsquo;<samp>4.0</samp>&rsquo;, &lsquo;<samp>quad</samp>&rsquo;, &lsquo;<samp>5.0</samp>&rsquo;, etc.)

  1061. 

  1062. </li><li> a number of channels, in decimal, followed by &rsquo;c&rsquo;, yielding the default channel

  1063. layout for that number of channels (see the function

  1064. <code>av_channel_layout_default</code>). Note that not all channel counts have a

  1065. default layout.

  1066. 

  1067. </li><li> a number of channels, in decimal, followed by &rsquo;C&rsquo;, yielding an unknown channel

  1068. layout with the specified number of channels. Note that not all channel layout

  1069. specification strings support unknown channel layouts.

  1070. 

  1071. </li><li> a channel layout mask, in hexadecimal starting with &quot;0x&quot; (see the

  1072. <code>AV_CH_*</code> macros in <samp>libavutil/channel_layout.h</samp>.

  1073. </li></ul>

  1074. 

  1075. <p>Before libavutil version 53 the trailing character &quot;c&quot; to specify a number of

  1076. channels was optional, but now it is required, while a channel layout mask can

  1077. also be specified as a decimal number (if and only if not followed by &quot;c&quot; or &quot;C&quot;).

  1078. </p>

  1079. <p>See also the function <code>av_channel_layout_from_string</code> defined in

  1080. <samp>libavutil/channel_layout.h</samp>.

  1081. </p>

  1082. <a name="Expression-Evaluation"></a>

  1083. <h2 class="chapter">3 Expression Evaluation<span class="pull-right"><a class="anchor hidden-xs" href="#Expression-Evaluation" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Expression-Evaluation" aria-hidden="true">TOC</a></span></h2>

  1084. 

  1085. <p>When evaluating an arithmetic expression, FFmpeg uses an internal

  1086. formula evaluator, implemented through the <samp>libavutil/eval.h</samp>

  1087. interface.

  1088. </p>

  1089. <p>An expression may contain unary, binary operators, constants, and

  1090. functions.

  1091. </p>

  1092. <p>Two expressions <var>expr1</var> and <var>expr2</var> can be combined to form

  1093. another expression &quot;<var>expr1</var>;<var>expr2</var>&quot;.

  1094. <var>expr1</var> and <var>expr2</var> are evaluated in turn, and the new

  1095. expression evaluates to the value of <var>expr2</var>.

  1096. </p>

  1097. <p>The following binary operators are available: <code>+</code>, <code>-</code>,

  1098. <code>*</code>, <code>/</code>, <code>^</code>.

  1099. </p>

  1100. <p>The following unary operators are available: <code>+</code>, <code>-</code>.

  1101. </p>

  1102. <p>The following functions are available:

  1103. </p><dl compact="compact">

  1104. <dt><span><samp>abs(x)</samp></span></dt>

  1105. <dd><p>Compute absolute value of <var>x</var>.

  1106. </p>

  1107. </dd>

  1108. <dt><span><samp>acos(x)</samp></span></dt>

  1109. <dd><p>Compute arccosine of <var>x</var>.

  1110. </p>

  1111. </dd>

  1112. <dt><span><samp>asin(x)</samp></span></dt>

  1113. <dd><p>Compute arcsine of <var>x</var>.

  1114. </p>

  1115. </dd>

  1116. <dt><span><samp>atan(x)</samp></span></dt>

  1117. <dd><p>Compute arctangent of <var>x</var>.

  1118. </p>

  1119. </dd>

  1120. <dt><span><samp>atan2(x, y)</samp></span></dt>

  1121. <dd><p>Compute principal value of the arc tangent of <var>y</var>/<var>x</var>.

  1122. </p>

  1123. </dd>

  1124. <dt><span><samp>between(x, min, max)</samp></span></dt>

  1125. <dd><p>Return 1 if <var>x</var> is greater than or equal to <var>min</var> and lesser than or

  1126. equal to <var>max</var>, 0 otherwise.

  1127. </p>

  1128. </dd>

  1129. <dt><span><samp>bitand(x, y)</samp></span></dt>

  1130. <dt><span><samp>bitor(x, y)</samp></span></dt>

  1131. <dd><p>Compute bitwise and/or operation on <var>x</var> and <var>y</var>.

  1132. </p>

  1133. <p>The results of the evaluation of <var>x</var> and <var>y</var> are converted to

  1134. integers before executing the bitwise operation.

  1135. </p>

  1136. <p>Note that both the conversion to integer and the conversion back to

  1137. floating point can lose precision. Beware of unexpected results for

  1138. large numbers (usually 2^53 and larger).

  1139. </p>

  1140. </dd>

  1141. <dt><span><samp>ceil(expr)</samp></span></dt>

  1142. <dd><p>Round the value of expression <var>expr</var> upwards to the nearest

  1143. integer. For example, &quot;ceil(1.5)&quot; is &quot;2.0&quot;.

  1144. </p>

  1145. </dd>

  1146. <dt><span><samp>clip(x, min, max)</samp></span></dt>

  1147. <dd><p>Return the value of <var>x</var> clipped between <var>min</var> and <var>max</var>.

  1148. </p>

  1149. </dd>

  1150. <dt><span><samp>cos(x)</samp></span></dt>

  1151. <dd><p>Compute cosine of <var>x</var>.

  1152. </p>

  1153. </dd>

  1154. <dt><span><samp>cosh(x)</samp></span></dt>

  1155. <dd><p>Compute hyperbolic cosine of <var>x</var>.

  1156. </p>

  1157. </dd>

  1158. <dt><span><samp>eq(x, y)</samp></span></dt>

  1159. <dd><p>Return 1 if <var>x</var> and <var>y</var> are equivalent, 0 otherwise.

  1160. </p>

  1161. </dd>

  1162. <dt><span><samp>exp(x)</samp></span></dt>

  1163. <dd><p>Compute exponential of <var>x</var> (with base <code>e</code>, the Euler&rsquo;s number).

  1164. </p>

  1165. </dd>

  1166. <dt><span><samp>floor(expr)</samp></span></dt>

  1167. <dd><p>Round the value of expression <var>expr</var> downwards to the nearest

  1168. integer. For example, &quot;floor(-1.5)&quot; is &quot;-2.0&quot;.

  1169. </p>

  1170. </dd>

  1171. <dt><span><samp>gauss(x)</samp></span></dt>

  1172. <dd><p>Compute Gauss function of <var>x</var>, corresponding to

  1173. <code>exp(-x*x/2) / sqrt(2*PI)</code>.

  1174. </p>

  1175. </dd>

  1176. <dt><span><samp>gcd(x, y)</samp></span></dt>

  1177. <dd><p>Return the greatest common divisor of <var>x</var> and <var>y</var>. If both <var>x</var> and

  1178. <var>y</var> are 0 or either or both are less than zero then behavior is undefined.

  1179. </p>

  1180. </dd>

  1181. <dt><span><samp>gt(x, y)</samp></span></dt>

  1182. <dd><p>Return 1 if <var>x</var> is greater than <var>y</var>, 0 otherwise.

  1183. </p>

  1184. </dd>

  1185. <dt><span><samp>gte(x, y)</samp></span></dt>

  1186. <dd><p>Return 1 if <var>x</var> is greater than or equal to <var>y</var>, 0 otherwise.

  1187. </p>

  1188. </dd>

  1189. <dt><span><samp>hypot(x, y)</samp></span></dt>

  1190. <dd><p>This function is similar to the C function with the same name; it returns

  1191. &quot;sqrt(<var>x</var>*<var>x</var> + <var>y</var>*<var>y</var>)&quot;, the length of the hypotenuse of a

  1192. right triangle with sides of length <var>x</var> and <var>y</var>, or the distance of the

  1193. point (<var>x</var>, <var>y</var>) from the origin.

  1194. </p>

  1195. </dd>

  1196. <dt><span><samp>if(x, y)</samp></span></dt>

  1197. <dd><p>Evaluate <var>x</var>, and if the result is non-zero return the result of

  1198. the evaluation of <var>y</var>, return 0 otherwise.

  1199. </p>

  1200. </dd>

  1201. <dt><span><samp>if(x, y, z)</samp></span></dt>

  1202. <dd><p>Evaluate <var>x</var>, and if the result is non-zero return the evaluation

  1203. result of <var>y</var>, otherwise the evaluation result of <var>z</var>.

  1204. </p>

  1205. </dd>

  1206. <dt><span><samp>ifnot(x, y)</samp></span></dt>

  1207. <dd><p>Evaluate <var>x</var>, and if the result is zero return the result of the

  1208. evaluation of <var>y</var>, return 0 otherwise.

  1209. </p>

  1210. </dd>

  1211. <dt><span><samp>ifnot(x, y, z)</samp></span></dt>

  1212. <dd><p>Evaluate <var>x</var>, and if the result is zero return the evaluation

  1213. result of <var>y</var>, otherwise the evaluation result of <var>z</var>.

  1214. </p>

  1215. </dd>

  1216. <dt><span><samp>isinf(x)</samp></span></dt>

  1217. <dd><p>Return 1.0 if <var>x</var> is +/-INFINITY, 0.0 otherwise.

  1218. </p>

  1219. </dd>

  1220. <dt><span><samp>isnan(x)</samp></span></dt>

  1221. <dd><p>Return 1.0 if <var>x</var> is NAN, 0.0 otherwise.

  1222. </p>

  1223. </dd>

  1224. <dt><span><samp>ld(var)</samp></span></dt>

  1225. <dd><p>Load the value of the internal variable with number

  1226. <var>var</var>, which was previously stored with st(<var>var</var>, <var>expr</var>).

  1227. The function returns the loaded value.

  1228. </p>

  1229. </dd>

  1230. <dt><span><samp>lerp(x, y, z)</samp></span></dt>

  1231. <dd><p>Return linear interpolation between <var>x</var> and <var>y</var> by amount of <var>z</var>.

  1232. </p>

  1233. </dd>

  1234. <dt><span><samp>log(x)</samp></span></dt>

  1235. <dd><p>Compute natural logarithm of <var>x</var>.

  1236. </p>

  1237. </dd>

  1238. <dt><span><samp>lt(x, y)</samp></span></dt>

  1239. <dd><p>Return 1 if <var>x</var> is lesser than <var>y</var>, 0 otherwise.

  1240. </p>

  1241. </dd>

  1242. <dt><span><samp>lte(x, y)</samp></span></dt>

  1243. <dd><p>Return 1 if <var>x</var> is lesser than or equal to <var>y</var>, 0 otherwise.

  1244. </p>

  1245. </dd>

  1246. <dt><span><samp>max(x, y)</samp></span></dt>

  1247. <dd><p>Return the maximum between <var>x</var> and <var>y</var>.

  1248. </p>

  1249. </dd>

  1250. <dt><span><samp>min(x, y)</samp></span></dt>

  1251. <dd><p>Return the minimum between <var>x</var> and <var>y</var>.

  1252. </p>

  1253. </dd>

  1254. <dt><span><samp>mod(x, y)</samp></span></dt>

  1255. <dd><p>Compute the remainder of division of <var>x</var> by <var>y</var>.

  1256. </p>

  1257. </dd>

  1258. <dt><span><samp>not(expr)</samp></span></dt>

  1259. <dd><p>Return 1.0 if <var>expr</var> is zero, 0.0 otherwise.

  1260. </p>

  1261. </dd>

  1262. <dt><span><samp>pow(x, y)</samp></span></dt>

  1263. <dd><p>Compute the power of <var>x</var> elevated <var>y</var>, it is equivalent to

  1264. &quot;(<var>x</var>)^(<var>y</var>)&quot;.

  1265. </p>

  1266. </dd>

  1267. <dt><span><samp>print(t)</samp></span></dt>

  1268. <dt><span><samp>print(t, l)</samp></span></dt>

  1269. <dd><p>Print the value of expression <var>t</var> with loglevel <var>l</var>. If

  1270. <var>l</var> is not specified then a default log level is used.

  1271. Returns the value of the expression printed.

  1272. </p>

  1273. <p>Prints t with loglevel l

  1274. </p>

  1275. </dd>

  1276. <dt><span><samp>random(x)</samp></span></dt>

  1277. <dd><p>Return a pseudo random value between 0.0 and 1.0. <var>x</var> is the index of the

  1278. internal variable which will be used to save the seed/state.

  1279. </p>

  1280. </dd>

  1281. <dt><span><samp>root(expr, max)</samp></span></dt>

  1282. <dd><p>Find an input value for which the function represented by <var>expr</var>

  1283. with argument <var>ld(0)</var> is 0 in the interval 0..<var>max</var>.

  1284. </p>

  1285. <p>The expression in <var>expr</var> must denote a continuous function or the

  1286. result is undefined.

  1287. </p>

  1288. <p><var>ld(0)</var> is used to represent the function input value, which means

  1289. that the given expression will be evaluated multiple times with

  1290. various input values that the expression can access through

  1291. <code>ld(0)</code>. When the expression evaluates to 0 then the

  1292. corresponding input value will be returned.

  1293. </p>

  1294. </dd>

  1295. <dt><span><samp>round(expr)</samp></span></dt>

  1296. <dd><p>Round the value of expression <var>expr</var> to the nearest integer. For example, &quot;round(1.5)&quot; is &quot;2.0&quot;.

  1297. </p>

  1298. </dd>

  1299. <dt><span><samp>sgn(x)</samp></span></dt>

  1300. <dd><p>Compute sign of <var>x</var>.

  1301. </p>

  1302. </dd>

  1303. <dt><span><samp>sin(x)</samp></span></dt>

  1304. <dd><p>Compute sine of <var>x</var>.

  1305. </p>

  1306. </dd>

  1307. <dt><span><samp>sinh(x)</samp></span></dt>

  1308. <dd><p>Compute hyperbolic sine of <var>x</var>.

  1309. </p>

  1310. </dd>

  1311. <dt><span><samp>sqrt(expr)</samp></span></dt>

  1312. <dd><p>Compute the square root of <var>expr</var>. This is equivalent to

  1313. &quot;(<var>expr</var>)^.5&quot;.

  1314. </p>

  1315. </dd>

  1316. <dt><span><samp>squish(x)</samp></span></dt>

  1317. <dd><p>Compute expression <code>1/(1 + exp(4*x))</code>.

  1318. </p>

  1319. </dd>

  1320. <dt><span><samp>st(var, expr)</samp></span></dt>

  1321. <dd><p>Store the value of the expression <var>expr</var> in an internal

  1322. variable. <var>var</var> specifies the number of the variable where to

  1323. store the value, and it is a value ranging from 0 to 9. The function

  1324. returns the value stored in the internal variable.

  1325. Note, Variables are currently not shared between expressions.

  1326. </p>

  1327. </dd>

  1328. <dt><span><samp>tan(x)</samp></span></dt>

  1329. <dd><p>Compute tangent of <var>x</var>.

  1330. </p>

  1331. </dd>

  1332. <dt><span><samp>tanh(x)</samp></span></dt>

  1333. <dd><p>Compute hyperbolic tangent of <var>x</var>.

  1334. </p>

  1335. </dd>

  1336. <dt><span><samp>taylor(expr, x)</samp></span></dt>

  1337. <dt><span><samp>taylor(expr, x, id)</samp></span></dt>

  1338. <dd><p>Evaluate a Taylor series at <var>x</var>, given an expression representing

  1339. the <code>ld(id)</code>-th derivative of a function at 0.

  1340. </p>

  1341. <p>When the series does not converge the result is undefined.

  1342. </p>

  1343. <p><var>ld(id)</var> is used to represent the derivative order in <var>expr</var>,

  1344. which means that the given expression will be evaluated multiple times

  1345. with various input values that the expression can access through

  1346. <code>ld(id)</code>. If <var>id</var> is not specified then 0 is assumed.

  1347. </p>

  1348. <p>Note, when you have the derivatives at y instead of 0,

  1349. <code>taylor(expr, x-y)</code> can be used.

  1350. </p>

  1351. </dd>

  1352. <dt><span><samp>time(0)</samp></span></dt>

  1353. <dd><p>Return the current (wallclock) time in seconds.

  1354. </p>

  1355. </dd>

  1356. <dt><span><samp>trunc(expr)</samp></span></dt>

  1357. <dd><p>Round the value of expression <var>expr</var> towards zero to the nearest

  1358. integer. For example, &quot;trunc(-1.5)&quot; is &quot;-1.0&quot;.

  1359. </p>

  1360. </dd>

  1361. <dt><span><samp>while(cond, expr)</samp></span></dt>

  1362. <dd><p>Evaluate expression <var>expr</var> while the expression <var>cond</var> is

  1363. non-zero, and returns the value of the last <var>expr</var> evaluation, or

  1364. NAN if <var>cond</var> was always false.

  1365. </p></dd>

  1366. </dl>

  1367. 

  1368. <p>The following constants are available:

  1369. </p><dl compact="compact">

  1370. <dt><span><samp>PI</samp></span></dt>

  1371. <dd><p>area of the unit disc, approximately 3.14

  1372. </p></dd>

  1373. <dt><span><samp>E</samp></span></dt>

  1374. <dd><p>exp(1) (Euler&rsquo;s number), approximately 2.718

  1375. </p></dd>

  1376. <dt><span><samp>PHI</samp></span></dt>

  1377. <dd><p>golden ratio (1+sqrt(5))/2, approximately 1.618

  1378. </p></dd>

  1379. </dl>

  1380. 

  1381. <p>Assuming that an expression is considered &quot;true&quot; if it has a non-zero

  1382. value, note that:

  1383. </p>

  1384. <p><code>*</code> works like AND

  1385. </p>

  1386. <p><code>+</code> works like OR

  1387. </p>

  1388. <p>For example the construct:

  1389. </p><div class="example">

  1390. <pre class="example">if (A AND B) then C

  1391. </pre></div>

  1392. <p>is equivalent to:

  1393. </p><div class="example">

  1394. <pre class="example">if(A*B, C)

  1395. </pre></div>

  1396. 

  1397. <p>In your C code, you can extend the list of unary and binary functions,

  1398. and define recognized constants, so that they are available for your

  1399. expressions.

  1400. </p>

  1401. <p>The evaluator also recognizes the International System unit prefixes.

  1402. If &rsquo;i&rsquo; is appended after the prefix, binary prefixes are used, which

  1403. are based on powers of 1024 instead of powers of 1000.

  1404. The &rsquo;B&rsquo; postfix multiplies the value by 8, and can be appended after a

  1405. unit prefix or used alone. This allows using for example &rsquo;KB&rsquo;, &rsquo;MiB&rsquo;,

  1406. &rsquo;G&rsquo; and &rsquo;B&rsquo; as number postfix.

  1407. </p>

  1408. <p>The list of available International System prefixes follows, with

  1409. indication of the corresponding powers of 10 and of 2.

  1410. </p><dl compact="compact">

  1411. <dt><span><samp>y</samp></span></dt>

  1412. <dd><p>10^-24 / 2^-80

  1413. </p></dd>

  1414. <dt><span><samp>z</samp></span></dt>

  1415. <dd><p>10^-21 / 2^-70

  1416. </p></dd>

  1417. <dt><span><samp>a</samp></span></dt>

  1418. <dd><p>10^-18 / 2^-60

  1419. </p></dd>

  1420. <dt><span><samp>f</samp></span></dt>

  1421. <dd><p>10^-15 / 2^-50

  1422. </p></dd>

  1423. <dt><span><samp>p</samp></span></dt>

  1424. <dd><p>10^-12 / 2^-40

  1425. </p></dd>

  1426. <dt><span><samp>n</samp></span></dt>

  1427. <dd><p>10^-9 / 2^-30

  1428. </p></dd>

  1429. <dt><span><samp>u</samp></span></dt>

  1430. <dd><p>10^-6 / 2^-20

  1431. </p></dd>

  1432. <dt><span><samp>m</samp></span></dt>

  1433. <dd><p>10^-3 / 2^-10

  1434. </p></dd>

  1435. <dt><span><samp>c</samp></span></dt>

  1436. <dd><p>10^-2

  1437. </p></dd>

  1438. <dt><span><samp>d</samp></span></dt>

  1439. <dd><p>10^-1

  1440. </p></dd>

  1441. <dt><span><samp>h</samp></span></dt>

  1442. <dd><p>10^2

  1443. </p></dd>

  1444. <dt><span><samp>k</samp></span></dt>

  1445. <dd><p>10^3 / 2^10

  1446. </p></dd>

  1447. <dt><span><samp>K</samp></span></dt>

  1448. <dd><p>10^3 / 2^10

  1449. </p></dd>

  1450. <dt><span><samp>M</samp></span></dt>

  1451. <dd><p>10^6 / 2^20

  1452. </p></dd>

  1453. <dt><span><samp>G</samp></span></dt>

  1454. <dd><p>10^9 / 2^30

  1455. </p></dd>

  1456. <dt><span><samp>T</samp></span></dt>

  1457. <dd><p>10^12 / 2^40

  1458. </p></dd>

  1459. <dt><span><samp>P</samp></span></dt>

  1460. <dd><p>10^15 / 2^50

  1461. </p></dd>

  1462. <dt><span><samp>E</samp></span></dt>

  1463. <dd><p>10^18 / 2^60

  1464. </p></dd>

  1465. <dt><span><samp>Z</samp></span></dt>

  1466. <dd><p>10^21 / 2^70

  1467. </p></dd>

  1468. <dt><span><samp>Y</samp></span></dt>

  1469. <dd><p>10^24 / 2^80

  1470. </p></dd>

  1471. </dl>

  1472. 

  1473. 

  1474. <a name="See-Also"></a>

  1475. <h2 class="chapter">4 See Also<span class="pull-right"><a class="anchor hidden-xs" href="#See-Also" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-See-Also" aria-hidden="true">TOC</a></span></h2>

  1476. 

  1477. <p><a href="ffmpeg.html">ffmpeg</a>, <a href="ffplay.html">ffplay</a>, <a href="ffprobe.html">ffprobe</a>,

  1478. <a href="libavutil.html">libavutil</a>

  1479. </p>

  1480. 

  1481. <a name="Authors"></a>

  1482. <h2 class="chapter">5 Authors<span class="pull-right"><a class="anchor hidden-xs" href="#Authors" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Authors" aria-hidden="true">TOC</a></span></h2>

  1483. 

  1484. <p>The FFmpeg developers.

  1485. </p>

  1486. <p>For details about the authorship, see the Git history of the project

  1487. (https://git.ffmpeg.org/ffmpeg), e.g. by typing the command

  1488. <code>git log</code> in the FFmpeg source directory, or browsing the

  1489. online repository at <a href="https://git.ffmpeg.org/ffmpeg">https://git.ffmpeg.org/ffmpeg</a>.

  1490. </p>

  1491. <p>Maintainers for the specific components are listed in the file

  1492. <samp>MAINTAINERS</samp> in the source code tree.

  1493. </p>

  1494. 

  1495.       <p style="font-size: small;">

  1496.         This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.

  1497.       </p>

  1498.     </div>

  1499.   </body>

  1500. </html>