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

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  7.       FFmpeg FAQ

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  15.       <h1>

  16.       FFmpeg FAQ

  17.       </h1>

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  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-General-Questions" href="#General-Questions">1 General Questions</a>

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

  32.     <li><a id="toc-Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f" href="#Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f">1.1 Why doesn&rsquo;t FFmpeg support feature [xyz]?</a></li>

  33.     <li><a id="toc-FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f" href="#FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f">1.2 FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it?</a></li>

  34.     <li><a id="toc-I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e" href="#I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e">1.3 I cannot read this file although this format seems to be supported by ffmpeg.</a></li>

  35.     <li><a id="toc-Which-codecs-are-supported-by-Windows_003f" href="#Which-codecs-are-supported-by-Windows_003f">1.4 Which codecs are supported by Windows?</a></li>

  36.   </ul></li>

  37.   <li><a id="toc-Compilation" href="#Compilation">2 Compilation</a>

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

  39.     <li><a id="toc-error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027" href="#error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027">2.1 <code>error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'</code></a></li>

  40.     <li><a id="toc-I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f" href="#I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f">2.2 I have installed this library with my distro&rsquo;s package manager. Why does <code>configure</code> not see it?</a></li>

  41.     <li><a id="toc-How-do-I-make-pkg_002dconfig-find-my-libraries_003f" href="#How-do-I-make-pkg_002dconfig-find-my-libraries_003f">2.3 How do I make <code>pkg-config</code> find my libraries?</a></li>

  42.     <li><a id="toc-How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f" href="#How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f">2.4 How do I use <code>pkg-config</code> when cross-compiling?</a></li>

  43.   </ul></li>

  44.   <li><a id="toc-Usage" href="#Usage">3 Usage</a>

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

  46.     <li><a id="toc-ffmpeg-does-not-work_003b-what-is-wrong_003f" href="#ffmpeg-does-not-work_003b-what-is-wrong_003f">3.1 ffmpeg does not work; what is wrong?</a></li>

  47.     <li><a id="toc-How-do-I-encode-single-pictures-into-movies_003f" href="#How-do-I-encode-single-pictures-into-movies_003f">3.2 How do I encode single pictures into movies?</a></li>

  48.     <li><a id="toc-How-do-I-encode-movie-to-single-pictures_003f" href="#How-do-I-encode-movie-to-single-pictures_003f">3.3 How do I encode movie to single pictures?</a></li>

  49.     <li><a id="toc-Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f" href="#Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f">3.4 Why do I see a slight quality degradation with multithreaded MPEG* encoding?</a></li>

  50.     <li><a id="toc-How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f" href="#How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f">3.5 How can I read from the standard input or write to the standard output?</a></li>

  51.     <li><a id="toc-_002df-jpeg-doesn_0027t-work_002e" href="#g_t_002df-jpeg-doesn_0027t-work_002e">3.6 -f jpeg doesn&rsquo;t work.</a></li>

  52.     <li><a id="toc-Why-can-I-not-change-the-frame-rate_003f" href="#Why-can-I-not-change-the-frame-rate_003f">3.7 Why can I not change the frame rate?</a></li>

  53.     <li><a id="toc-How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f" href="#How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f">3.8 How do I encode Xvid or DivX video with ffmpeg?</a></li>

  54.     <li><a id="toc-Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f" href="#Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f">3.9 Which are good parameters for encoding high quality MPEG-4?</a></li>

  55.     <li><a id="toc-Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f" href="#Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f">3.10 Which are good parameters for encoding high quality MPEG-1/MPEG-2?</a></li>

  56.     <li><a id="toc-Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f" href="#Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f">3.11 Interlaced video looks very bad when encoded with ffmpeg, what is wrong?</a></li>

  57.     <li><a id="toc-How-can-I-read-DirectShow-files_003f" href="#How-can-I-read-DirectShow-files_003f">3.12 How can I read DirectShow files?</a></li>

  58.     <li><a id="toc-How-can-I-join-video-files_003f" href="#How-can-I-join-video-files_003f">3.13 How can I join video files?</a></li>

  59.     <li><a id="toc-How-can-I-concatenate-video-files_003f" href="#How-can-I-concatenate-video-files_003f">3.14 How can I concatenate video files?</a>

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

  61.       <li><a id="toc-Concatenating-using-the-concat-filter" href="#Concatenating-using-the-concat-filter">3.14.1 Concatenating using the concat <em>filter</em></a></li>

  62.       <li><a id="toc-Concatenating-using-the-concat-demuxer" href="#Concatenating-using-the-concat-demuxer">3.14.2 Concatenating using the concat <em>demuxer</em></a></li>

  63.       <li><a id="toc-Concatenating-using-the-concat-protocol-_0028file-level_0029" href="#Concatenating-using-the-concat-protocol-_0028file-level_0029">3.14.3 Concatenating using the concat <em>protocol</em> (file level)</a></li>

  64.       <li><a id="toc-Concatenating-using-raw-audio-and-video" href="#Concatenating-using-raw-audio-and-video">3.14.4 Concatenating using raw audio and video</a></li>

  65.     </ul></li>

  66.     <li><a id="toc-Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e" href="#Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e">3.15 Using <samp>-f lavfi</samp>, audio becomes mono for no apparent reason.</a></li>

  67.     <li><a id="toc-Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f" href="#Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f">3.16 Why does FFmpeg not see the subtitles in my VOB file?</a></li>

  68.     <li><a id="toc-Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f" href="#Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f">3.17 Why was the <code>ffmpeg</code> <samp>-sameq</samp> option removed? What to use instead?</a></li>

  69.     <li><a id="toc-I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f" href="#I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f">3.18 I have a stretched video, why does scaling does not fix it?</a></li>

  70.     <li><a id="toc-How-do-I-run-ffmpeg-as-a-background-task_003f" href="#How-do-I-run-ffmpeg-as-a-background-task_003f">3.19 How do I run ffmpeg as a background task?</a></li>

  71.     <li><a id="toc-How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f" href="#How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f">3.20 How do I prevent ffmpeg from suspending with a message like <em>suspended (tty output)</em>?</a></li>

  72.   </ul></li>

  73.   <li><a id="toc-Development" href="#Development">4 Development</a>

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

  75.     <li><a id="toc-Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f" href="#Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f">4.1 Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat?</a></li>

  76.     <li><a id="toc-Can-you-support-my-C-compiler-XXX_003f" href="#Can-you-support-my-C-compiler-XXX_003f">4.2 Can you support my C compiler XXX?</a></li>

  77.     <li><a id="toc-Is-Microsoft-Visual-C_002b_002b-supported_003f" href="#Is-Microsoft-Visual-C_002b_002b-supported_003f">4.3 Is Microsoft Visual C++ supported?</a></li>

  78.     <li><a id="toc-Can-you-add-automake_002c-libtool-or-autoconf-support_003f" href="#Can-you-add-automake_002c-libtool-or-autoconf-support_003f">4.4 Can you add automake, libtool or autoconf support?</a></li>

  79.     <li><a id="toc-Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f" href="#Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f">4.5 Why not rewrite FFmpeg in object-oriented C++?</a></li>

  80.     <li><a id="toc-Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f" href="#Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f">4.6 Why are the ffmpeg programs devoid of debugging symbols?</a></li>

  81.     <li><a id="toc-I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f" href="#I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f">4.7 I do not like the LGPL, can I contribute code under the GPL instead?</a></li>

  82.     <li><a id="toc-I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e" href="#I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e">4.8 I&rsquo;m using FFmpeg from within my C application but the linker complains about missing symbols from the libraries themselves.</a></li>

  83.     <li><a id="toc-I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e" href="#I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e">4.9 I&rsquo;m using FFmpeg from within my C++ application but the linker complains about missing symbols which seem to be available.</a></li>

  84.     <li><a id="toc-I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope" href="#I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope">4.10 I&rsquo;m using libavutil from within my C++ application but the compiler complains about &rsquo;UINT64_C&rsquo; was not declared in this scope</a></li>

  85.     <li><a id="toc-I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f" href="#I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f">4.11 I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat?</a></li>

  86.     <li><a id="toc-Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f" href="#Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f">4.12 Where is the documentation about ffv1, msmpeg4, asv1, 4xm?</a></li>

  87.     <li><a id="toc-How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f" href="#How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f">4.13 How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?</a></li>

  88.     <li><a id="toc-AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e" href="#AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e">4.14 AVStream.r_frame_rate is wrong, it is much larger than the frame rate.</a></li>

  89.     <li><a id="toc-Why-is-make-fate-not-running-all-tests_003f" href="#Why-is-make-fate-not-running-all-tests_003f">4.15 Why is <code>make fate</code> not running all tests?</a></li>

  90.     <li><a id="toc-Why-is-make-fate-not-finding-the-samples_003f" href="#Why-is-make-fate-not-finding-the-samples_003f">4.16 Why is <code>make fate</code> not finding the samples?</a></li>

  91.   </ul></li>

  92. </ul>

  93. </div>

  94. </div>

  95. 

  96. <a name="General-Questions"></a>

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

  98. 

  99. <a name="Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f"></a>

  100. <h3 class="section">1.1 Why doesn&rsquo;t FFmpeg support feature [xyz]?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f" aria-hidden="true">TOC</a></span></h3>

  101. 

  102. <p>Because no one has taken on that task yet. FFmpeg development is

  103. driven by the tasks that are important to the individual developers.

  104. If there is a feature that is important to you, the best way to get

  105. it implemented is to undertake the task yourself or sponsor a developer.

  106. </p>

  107. <a name="FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f"></a>

  108. <h3 class="section">1.2 FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it?<span class="pull-right"><a class="anchor hidden-xs" href="#FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f" aria-hidden="true">TOC</a></span></h3>

  109. 

  110. <p>No. Windows DLLs are not portable, bloated and often slow.

  111. Moreover FFmpeg strives to support all codecs natively.

  112. A DLL loader is not conducive to that goal.

  113. </p>

  114. <a name="I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e"></a>

  115. <h3 class="section">1.3 I cannot read this file although this format seems to be supported by ffmpeg.<span class="pull-right"><a class="anchor hidden-xs" href="#I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e" aria-hidden="true">TOC</a></span></h3>

  116. 

  117. <p>Even if ffmpeg can read the container format, it may not support all its

  118. codecs. Please consult the supported codec list in the ffmpeg

  119. documentation.

  120. </p>

  121. <a name="Which-codecs-are-supported-by-Windows_003f"></a>

  122. <h3 class="section">1.4 Which codecs are supported by Windows?<span class="pull-right"><a class="anchor hidden-xs" href="#Which-codecs-are-supported-by-Windows_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Which-codecs-are-supported-by-Windows_003f" aria-hidden="true">TOC</a></span></h3>

  123. 

  124. <p>Windows does not support standard formats like MPEG very well, unless you

  125. install some additional codecs.

  126. </p>

  127. <p>The following list of video codecs should work on most Windows systems:

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

  129. <dt><span><samp>msmpeg4v2</samp></span></dt>

  130. <dd><p>.avi/.asf

  131. </p></dd>

  132. <dt><span><samp>msmpeg4</samp></span></dt>

  133. <dd><p>.asf only

  134. </p></dd>

  135. <dt><span><samp>wmv1</samp></span></dt>

  136. <dd><p>.asf only

  137. </p></dd>

  138. <dt><span><samp>wmv2</samp></span></dt>

  139. <dd><p>.asf only

  140. </p></dd>

  141. <dt><span><samp>mpeg4</samp></span></dt>

  142. <dd><p>Only if you have some MPEG-4 codec like ffdshow or Xvid installed.

  143. </p></dd>

  144. <dt><span><samp>mpeg1video</samp></span></dt>

  145. <dd><p>.mpg only

  146. </p></dd>

  147. </dl>

  148. <p>Note, ASF files often have .wmv or .wma extensions in Windows. It should also

  149. be mentioned that Microsoft claims a patent on the ASF format, and may sue

  150. or threaten users who create ASF files with non-Microsoft software. It is

  151. strongly advised to avoid ASF where possible.

  152. </p>

  153. <p>The following list of audio codecs should work on most Windows systems:

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

  155. <dt><span><samp>adpcm_ima_wav</samp></span></dt>

  156. <dt><span><samp>adpcm_ms</samp></span></dt>

  157. <dt><span><samp>pcm_s16le</samp></span></dt>

  158. <dd><p>always

  159. </p></dd>

  160. <dt><span><samp>libmp3lame</samp></span></dt>

  161. <dd><p>If some MP3 codec like LAME is installed.

  162. </p></dd>

  163. </dl>

  164. 

  165. 

  166. <a name="Compilation"></a>

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

  168. 

  169. <a name="error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027"></a>

  170. <h3 class="section">2.1 <code>error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'</code><span class="pull-right"><a class="anchor hidden-xs" href="#error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027" aria-hidden="true">TOC</a></span></h3>

  171. 

  172. <p>This is a bug in gcc. Do not report it to us. Instead, please report it to

  173. the gcc developers. Note that we will not add workarounds for gcc bugs.

  174. </p>

  175. <p>Also note that (some of) the gcc developers believe this is not a bug or

  176. not a bug they should fix:

  177. <a href="https://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203">https://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203</a>.

  178. Then again, some of them do not know the difference between an undecidable

  179. problem and an NP-hard problem...

  180. </p>

  181. <a name="I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f"></a>

  182. <h3 class="section">2.2 I have installed this library with my distro&rsquo;s package manager. Why does <code>configure</code> not see it?<span class="pull-right"><a class="anchor hidden-xs" href="#I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f" aria-hidden="true">TOC</a></span></h3>

  183. 

  184. <p>Distributions usually split libraries in several packages. The main package

  185. contains the files necessary to run programs using the library. The

  186. development package contains the files necessary to build programs using the

  187. library. Sometimes, docs and/or data are in a separate package too.

  188. </p>

  189. <p>To build FFmpeg, you need to install the development package. It is usually

  190. called <samp>libfoo-dev</samp> or <samp>libfoo-devel</samp>. You can remove it after the

  191. build is finished, but be sure to keep the main package.

  192. </p>

  193. <a name="How-do-I-make-pkg_002dconfig-find-my-libraries_003f"></a>

  194. <h3 class="section">2.3 How do I make <code>pkg-config</code> find my libraries?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-make-pkg_002dconfig-find-my-libraries_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-make-pkg_002dconfig-find-my-libraries_003f" aria-hidden="true">TOC</a></span></h3>

  195. 

  196. <p>Somewhere along with your libraries, there is a <samp>.pc</samp> file (or several)

  197. in a <samp>pkgconfig</samp> directory. You need to set environment variables to

  198. point <code>pkg-config</code> to these files.

  199. </p>

  200. <p>If you need to <em>add</em> directories to <code>pkg-config</code>&rsquo;s search list

  201. (typical use case: library installed separately), add it to

  202. <code>$PKG_CONFIG_PATH</code>:

  203. </p>

  204. <div class="example">

  205. <pre class="example">export PKG_CONFIG_PATH=/opt/x264/lib/pkgconfig:/opt/opus/lib/pkgconfig

  206. </pre></div>

  207. 

  208. <p>If you need to <em>replace</em> <code>pkg-config</code>&rsquo;s search list

  209. (typical use case: cross-compiling), set it in

  210. <code>$PKG_CONFIG_LIBDIR</code>:

  211. </p>

  212. <div class="example">

  213. <pre class="example">export PKG_CONFIG_LIBDIR=/home/me/cross/usr/lib/pkgconfig:/home/me/cross/usr/local/lib/pkgconfig

  214. </pre></div>

  215. 

  216. <p>If you need to know the library&rsquo;s internal dependencies (typical use: static

  217. linking), add the <code>--static</code> option to <code>pkg-config</code>:

  218. </p>

  219. <div class="example">

  220. <pre class="example">./configure --pkg-config-flags=--static

  221. </pre></div>

  222. 

  223. <a name="How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f"></a>

  224. <h3 class="section">2.4 How do I use <code>pkg-config</code> when cross-compiling?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f" aria-hidden="true">TOC</a></span></h3>

  225. 

  226. <p>The best way is to install <code>pkg-config</code> in your cross-compilation

  227. environment. It will automatically use the cross-compilation libraries.

  228. </p>

  229. <p>You can also use <code>pkg-config</code> from the host environment by

  230. specifying explicitly <code>--pkg-config=pkg-config</code> to <code>configure</code>.

  231. In that case, you must point <code>pkg-config</code> to the correct directories

  232. using the <code>PKG_CONFIG_LIBDIR</code>, as explained in the previous entry.

  233. </p>

  234. <p>As an intermediate solution, you can place in your cross-compilation

  235. environment a script that calls the host <code>pkg-config</code> with

  236. <code>PKG_CONFIG_LIBDIR</code> set. That script can look like that:

  237. </p>

  238. <div class="example">

  239. <pre class="example">#!/bin/sh

  240. PKG_CONFIG_LIBDIR=/path/to/cross/lib/pkgconfig

  241. export PKG_CONFIG_LIBDIR

  242. exec /usr/bin/pkg-config &quot;$@&quot;

  243. </pre></div>

  244. 

  245. <a name="Usage"></a>

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

  247. 

  248. <a name="ffmpeg-does-not-work_003b-what-is-wrong_003f"></a>

  249. <h3 class="section">3.1 ffmpeg does not work; what is wrong?<span class="pull-right"><a class="anchor hidden-xs" href="#ffmpeg-does-not-work_003b-what-is-wrong_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-ffmpeg-does-not-work_003b-what-is-wrong_003f" aria-hidden="true">TOC</a></span></h3>

  250. 

  251. <p>Try a <code>make distclean</code> in the ffmpeg source directory before the build.

  252. If this does not help see

  253. (<a href="https://ffmpeg.org/bugreports.html">https://ffmpeg.org/bugreports.html</a>).

  254. </p>

  255. <a name="How-do-I-encode-single-pictures-into-movies_003f"></a>

  256. <h3 class="section">3.2 How do I encode single pictures into movies?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-encode-single-pictures-into-movies_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-encode-single-pictures-into-movies_003f" aria-hidden="true">TOC</a></span></h3>

  257. 

  258. <p>First, rename your pictures to follow a numerical sequence.

  259. For example, img1.jpg, img2.jpg, img3.jpg,...

  260. Then you may run:

  261. </p>

  262. <div class="example">

  263. <pre class="example">ffmpeg -f image2 -i img%d.jpg /tmp/a.mpg

  264. </pre></div>

  265. 

  266. <p>Notice that &lsquo;<samp>%d</samp>&rsquo; is replaced by the image number.

  267. </p>

  268. <p><samp>img%03d.jpg</samp> means the sequence <samp>img001.jpg</samp>, <samp>img002.jpg</samp>, etc.

  269. </p>

  270. <p>Use the <samp>-start_number</samp> option to declare a starting number for

  271. the sequence. This is useful if your sequence does not start with

  272. <samp>img001.jpg</samp> but is still in a numerical order. The following

  273. example will start with <samp>img100.jpg</samp>:

  274. </p>

  275. <div class="example">

  276. <pre class="example">ffmpeg -f image2 -start_number 100 -i img%d.jpg /tmp/a.mpg

  277. </pre></div>

  278. 

  279. <p>If you have large number of pictures to rename, you can use the

  280. following command to ease the burden. The command, using the bourne

  281. shell syntax, symbolically links all files in the current directory

  282. that match <code>*jpg</code> to the <samp>/tmp</samp> directory in the sequence of

  283. <samp>img001.jpg</samp>, <samp>img002.jpg</samp> and so on.

  284. </p>

  285. <div class="example">

  286. <pre class="example">x=1; for i in *jpg; do counter=$(printf %03d $x); ln -s &quot;$i&quot; /tmp/img&quot;$counter&quot;.jpg; x=$(($x+1)); done

  287. </pre></div>

  288. 

  289. <p>If you want to sequence them by oldest modified first, substitute

  290. <code>$(ls -r -t *jpg)</code> in place of <code>*jpg</code>.

  291. </p>

  292. <p>Then run:

  293. </p>

  294. <div class="example">

  295. <pre class="example">ffmpeg -f image2 -i /tmp/img%03d.jpg /tmp/a.mpg

  296. </pre></div>

  297. 

  298. <p>The same logic is used for any image format that ffmpeg reads.

  299. </p>

  300. <p>You can also use <code>cat</code> to pipe images to ffmpeg:

  301. </p>

  302. <div class="example">

  303. <pre class="example">cat *.jpg | ffmpeg -f image2pipe -c:v mjpeg -i - output.mpg

  304. </pre></div>

  305. 

  306. <a name="How-do-I-encode-movie-to-single-pictures_003f"></a>

  307. <h3 class="section">3.3 How do I encode movie to single pictures?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-encode-movie-to-single-pictures_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-encode-movie-to-single-pictures_003f" aria-hidden="true">TOC</a></span></h3>

  308. 

  309. <p>Use:

  310. </p>

  311. <div class="example">

  312. <pre class="example">ffmpeg -i movie.mpg movie%d.jpg

  313. </pre></div>

  314. 

  315. <p>The <samp>movie.mpg</samp> used as input will be converted to

  316. <samp>movie1.jpg</samp>, <samp>movie2.jpg</samp>, etc...

  317. </p>

  318. <p>Instead of relying on file format self-recognition, you may also use

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

  320. <dt><span><samp>-c:v ppm</samp></span></dt>

  321. <dt><span><samp>-c:v png</samp></span></dt>

  322. <dt><span><samp>-c:v mjpeg</samp></span></dt>

  323. </dl>

  324. <p>to force the encoding.

  325. </p>

  326. <p>Applying that to the previous example:

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

  328. <pre class="example">ffmpeg -i movie.mpg -f image2 -c:v mjpeg menu%d.jpg

  329. </pre></div>

  330. 

  331. <p>Beware that there is no &quot;jpeg&quot; codec. Use &quot;mjpeg&quot; instead.

  332. </p>

  333. <a name="Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f"></a>

  334. <h3 class="section">3.4 Why do I see a slight quality degradation with multithreaded MPEG* encoding?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f" aria-hidden="true">TOC</a></span></h3>

  335. 

  336. <p>For multithreaded MPEG* encoding, the encoded slices must be independent,

  337. otherwise thread n would practically have to wait for n-1 to finish, so it&rsquo;s

  338. quite logical that there is a small reduction of quality. This is not a bug.

  339. </p>

  340. <a name="How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f"></a>

  341. <h3 class="section">3.5 How can I read from the standard input or write to the standard output?<span class="pull-right"><a class="anchor hidden-xs" href="#How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f" aria-hidden="true">TOC</a></span></h3>

  342. 

  343. <p>Use <samp>-</samp> as file name.

  344. </p>

  345. <a name="g_t_002df-jpeg-doesn_0027t-work_002e"></a>

  346. <h3 class="section">3.6 -f jpeg doesn&rsquo;t work.<span class="pull-right"><a class="anchor hidden-xs" href="#_002df-jpeg-doesn_0027t-work_002e" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-_002df-jpeg-doesn_0027t-work_002e" aria-hidden="true">TOC</a></span></h3>

  347. 

  348. <p>Try &rsquo;-f image2 test%d.jpg&rsquo;.

  349. </p>

  350. <a name="Why-can-I-not-change-the-frame-rate_003f"></a>

  351. <h3 class="section">3.7 Why can I not change the frame rate?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-can-I-not-change-the-frame-rate_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-can-I-not-change-the-frame-rate_003f" aria-hidden="true">TOC</a></span></h3>

  352. 

  353. <p>Some codecs, like MPEG-1/2, only allow a small number of fixed frame rates.

  354. Choose a different codec with the -c:v command line option.

  355. </p>

  356. <a name="How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f"></a>

  357. <h3 class="section">3.8 How do I encode Xvid or DivX video with ffmpeg?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f" aria-hidden="true">TOC</a></span></h3>

  358. 

  359. <p>Both Xvid and DivX (version 4+) are implementations of the ISO MPEG-4

  360. standard (note that there are many other coding formats that use this

  361. same standard). Thus, use &rsquo;-c:v mpeg4&rsquo; to encode in these formats. The

  362. default fourcc stored in an MPEG-4-coded file will be &rsquo;FMP4&rsquo;. If you want

  363. a different fourcc, use the &rsquo;-vtag&rsquo; option. E.g., &rsquo;-vtag xvid&rsquo; will

  364. force the fourcc &rsquo;xvid&rsquo; to be stored as the video fourcc rather than the

  365. default.

  366. </p>

  367. <a name="Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f"></a>

  368. <h3 class="section">3.9 Which are good parameters for encoding high quality MPEG-4?<span class="pull-right"><a class="anchor hidden-xs" href="#Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f" aria-hidden="true">TOC</a></span></h3>

  369. 

  370. <p>&rsquo;-mbd rd -flags +mv4+aic -trellis 2 -cmp 2 -subcmp 2 -g 300 -pass 1/2&rsquo;,

  371. things to try: &rsquo;-bf 2&rsquo;, &rsquo;-mpv_flags qp_rd&rsquo;, &rsquo;-mpv_flags mv0&rsquo;, &rsquo;-mpv_flags skip_rd&rsquo;.

  372. </p>

  373. <a name="Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f"></a>

  374. <h3 class="section">3.10 Which are good parameters for encoding high quality MPEG-1/MPEG-2?<span class="pull-right"><a class="anchor hidden-xs" href="#Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f" aria-hidden="true">TOC</a></span></h3>

  375. 

  376. <p>&rsquo;-mbd rd -trellis 2 -cmp 2 -subcmp 2 -g 100 -pass 1/2&rsquo;

  377. but beware the &rsquo;-g 100&rsquo; might cause problems with some decoders.

  378. Things to try: &rsquo;-bf 2&rsquo;, &rsquo;-mpv_flags qp_rd&rsquo;, &rsquo;-mpv_flags mv0&rsquo;, &rsquo;-mpv_flags skip_rd&rsquo;.

  379. </p>

  380. <a name="Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f"></a>

  381. <h3 class="section">3.11 Interlaced video looks very bad when encoded with ffmpeg, what is wrong?<span class="pull-right"><a class="anchor hidden-xs" href="#Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f" aria-hidden="true">TOC</a></span></h3>

  382. 

  383. <p>You should use &rsquo;-flags +ilme+ildct&rsquo; and maybe &rsquo;-flags +alt&rsquo; for interlaced

  384. material, and try &rsquo;-top 0/1&rsquo; if the result looks really messed-up.

  385. </p>

  386. <a name="How-can-I-read-DirectShow-files_003f"></a>

  387. <h3 class="section">3.12 How can I read DirectShow files?<span class="pull-right"><a class="anchor hidden-xs" href="#How-can-I-read-DirectShow-files_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-can-I-read-DirectShow-files_003f" aria-hidden="true">TOC</a></span></h3>

  388. 

  389. <p>If you have built FFmpeg with <code>./configure --enable-avisynth</code>

  390. (only possible on MinGW/Cygwin platforms),

  391. then you may use any file that DirectShow can read as input.

  392. </p>

  393. <p>Just create an &quot;input.avs&quot; text file with this single line ...

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

  395. <pre class="example">DirectShowSource(&quot;C:\path to your file\yourfile.asf&quot;)

  396. </pre></div>

  397. <p>... and then feed that text file to ffmpeg:

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

  399. <pre class="example">ffmpeg -i input.avs

  400. </pre></div>

  401. 

  402. <p>For ANY other help on AviSynth, please visit the

  403. <a href="http://www.avisynth.org/">AviSynth homepage</a>.

  404. </p>

  405. <a name="How-can-I-join-video-files_003f"></a>

  406. <h3 class="section">3.13 How can I join video files?<span class="pull-right"><a class="anchor hidden-xs" href="#How-can-I-join-video-files_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-can-I-join-video-files_003f" aria-hidden="true">TOC</a></span></h3>

  407. 

  408. <p>To &quot;join&quot; video files is quite ambiguous. The following list explains the

  409. different kinds of &quot;joining&quot; and points out how those are addressed in

  410. FFmpeg. To join video files may mean:

  411. </p>

  412. <ul>

  413. <li> To put them one after the other: this is called to <em>concatenate</em> them

  414. (in short: concat) and is addressed

  415. <a href="#How-can-I-concatenate-video-files">in this very faq</a>.

  416. 

  417. </li><li> To put them together in the same file, to let the user choose between the

  418. different versions (example: different audio languages): this is called to

  419. <em>multiplex</em> them together (in short: mux), and is done by simply

  420. invoking ffmpeg with several <samp>-i</samp> options.

  421. 

  422. </li><li> For audio, to put all channels together in a single stream (example: two

  423. mono streams into one stereo stream): this is sometimes called to

  424. <em>merge</em> them, and can be done using the

  425. <a href="ffmpeg-filters.html#amerge"><code>amerge</code></a> filter.

  426. 

  427. </li><li> For audio, to play one on top of the other: this is called to <em>mix</em>

  428. them, and can be done by first merging them into a single stream and then

  429. using the <a href="ffmpeg-filters.html#pan"><code>pan</code></a> filter to mix

  430. the channels at will.

  431. 

  432. </li><li> For video, to display both together, side by side or one on top of a part of

  433. the other; it can be done using the

  434. <a href="ffmpeg-filters.html#overlay"><code>overlay</code></a> video filter.

  435. 

  436. </li></ul>

  437. 

  438. <span id="How-can-I-concatenate-video-files"></span><a name="How-can-I-concatenate-video-files_003f"></a>

  439. <h3 class="section">3.14 How can I concatenate video files?<span class="pull-right"><a class="anchor hidden-xs" href="#How-can-I-concatenate-video-files_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-can-I-concatenate-video-files_003f" aria-hidden="true">TOC</a></span></h3>

  440. 

  441. <p>There are several solutions, depending on the exact circumstances.

  442. </p>

  443. <a name="Concatenating-using-the-concat-filter"></a>

  444. <h4 class="subsection">3.14.1 Concatenating using the concat <em>filter</em><span class="pull-right"><a class="anchor hidden-xs" href="#Concatenating-using-the-concat-filter" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Concatenating-using-the-concat-filter" aria-hidden="true">TOC</a></span></h4>

  445. 

  446. <p>FFmpeg has a <a href="ffmpeg-filters.html#concat"><code>concat</code></a> filter designed specifically for that, with examples in the

  447. documentation. This operation is recommended if you need to re-encode.

  448. </p>

  449. <a name="Concatenating-using-the-concat-demuxer"></a>

  450. <h4 class="subsection">3.14.2 Concatenating using the concat <em>demuxer</em><span class="pull-right"><a class="anchor hidden-xs" href="#Concatenating-using-the-concat-demuxer" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Concatenating-using-the-concat-demuxer" aria-hidden="true">TOC</a></span></h4>

  451. 

  452. <p>FFmpeg has a <a href="ffmpeg-formats.html#concat"><code>concat</code></a> demuxer which you can use when you want to avoid a re-encode and

  453. your format doesn&rsquo;t support file level concatenation.

  454. </p>

  455. <a name="Concatenating-using-the-concat-protocol-_0028file-level_0029"></a>

  456. <h4 class="subsection">3.14.3 Concatenating using the concat <em>protocol</em> (file level)<span class="pull-right"><a class="anchor hidden-xs" href="#Concatenating-using-the-concat-protocol-_0028file-level_0029" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Concatenating-using-the-concat-protocol-_0028file-level_0029" aria-hidden="true">TOC</a></span></h4>

  457. 

  458. <p>FFmpeg has a <a href="ffmpeg-protocols.html#concat"><code>concat</code></a> protocol designed specifically for that, with examples in the

  459. documentation.

  460. </p>

  461. <p>A few multimedia containers (MPEG-1, MPEG-2 PS, DV) allow one to concatenate

  462. video by merely concatenating the files containing them.

  463. </p>

  464. <p>Hence you may concatenate your multimedia files by first transcoding them to

  465. these privileged formats, then using the humble <code>cat</code> command (or the

  466. equally humble <code>copy</code> under Windows), and finally transcoding back to your

  467. format of choice.

  468. </p>

  469. <div class="example">

  470. <pre class="example">ffmpeg -i input1.avi -qscale:v 1 intermediate1.mpg

  471. ffmpeg -i input2.avi -qscale:v 1 intermediate2.mpg

  472. cat intermediate1.mpg intermediate2.mpg &gt; intermediate_all.mpg

  473. ffmpeg -i intermediate_all.mpg -qscale:v 2 output.avi

  474. </pre></div>

  475. 

  476. <p>Additionally, you can use the <code>concat</code> protocol instead of <code>cat</code> or

  477. <code>copy</code> which will avoid creation of a potentially huge intermediate file.

  478. </p>

  479. <div class="example">

  480. <pre class="example">ffmpeg -i input1.avi -qscale:v 1 intermediate1.mpg

  481. ffmpeg -i input2.avi -qscale:v 1 intermediate2.mpg

  482. ffmpeg -i concat:&quot;intermediate1.mpg|intermediate2.mpg&quot; -c copy intermediate_all.mpg

  483. ffmpeg -i intermediate_all.mpg -qscale:v 2 output.avi

  484. </pre></div>

  485. 

  486. <p>Note that you may need to escape the character &quot;|&quot; which is special for many

  487. shells.

  488. </p>

  489. <p>Another option is usage of named pipes, should your platform support it:

  490. </p>

  491. <div class="example">

  492. <pre class="example">mkfifo intermediate1.mpg

  493. mkfifo intermediate2.mpg

  494. ffmpeg -i input1.avi -qscale:v 1 -y intermediate1.mpg &lt; /dev/null &amp;

  495. ffmpeg -i input2.avi -qscale:v 1 -y intermediate2.mpg &lt; /dev/null &amp;

  496. cat intermediate1.mpg intermediate2.mpg |\

  497. ffmpeg -f mpeg -i - -c:v mpeg4 -c:a libmp3lame output.avi

  498. </pre></div>

  499. 

  500. <a name="Concatenating-using-raw-audio-and-video"></a>

  501. <h4 class="subsection">3.14.4 Concatenating using raw audio and video<span class="pull-right"><a class="anchor hidden-xs" href="#Concatenating-using-raw-audio-and-video" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Concatenating-using-raw-audio-and-video" aria-hidden="true">TOC</a></span></h4>

  502. 

  503. <p>Similarly, the yuv4mpegpipe format, and the raw video, raw audio codecs also

  504. allow concatenation, and the transcoding step is almost lossless.

  505. When using multiple yuv4mpegpipe(s), the first line needs to be discarded

  506. from all but the first stream. This can be accomplished by piping through

  507. <code>tail</code> as seen below. Note that when piping through <code>tail</code> you

  508. must use command grouping, <code>{  ;}</code>, to background properly.

  509. </p>

  510. <p>For example, let&rsquo;s say we want to concatenate two FLV files into an

  511. output.flv file:

  512. </p>

  513. <div class="example">

  514. <pre class="example">mkfifo temp1.a

  515. mkfifo temp1.v

  516. mkfifo temp2.a

  517. mkfifo temp2.v

  518. mkfifo all.a

  519. mkfifo all.v

  520. ffmpeg -i input1.flv -vn -f u16le -c:a pcm_s16le -ac 2 -ar 44100 - &gt; temp1.a &lt; /dev/null &amp;

  521. ffmpeg -i input2.flv -vn -f u16le -c:a pcm_s16le -ac 2 -ar 44100 - &gt; temp2.a &lt; /dev/null &amp;

  522. ffmpeg -i input1.flv -an -f yuv4mpegpipe - &gt; temp1.v &lt; /dev/null &amp;

  523. { ffmpeg -i input2.flv -an -f yuv4mpegpipe - &lt; /dev/null | tail -n +2 &gt; temp2.v ; } &amp;

  524. cat temp1.a temp2.a &gt; all.a &amp;

  525. cat temp1.v temp2.v &gt; all.v &amp;

  526. ffmpeg -f u16le -c:a pcm_s16le -ac 2 -ar 44100 -i all.a \

  527.        -f yuv4mpegpipe -i all.v \

  528.        -y output.flv

  529. rm temp[12].[av] all.[av]

  530. </pre></div>

  531. 

  532. <a name="Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e"></a>

  533. <h3 class="section">3.15 Using <samp>-f lavfi</samp>, audio becomes mono for no apparent reason.<span class="pull-right"><a class="anchor hidden-xs" href="#Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e" aria-hidden="true">TOC</a></span></h3>

  534. 

  535. <p>Use <samp>-dumpgraph -</samp> to find out exactly where the channel layout is

  536. lost.

  537. </p>

  538. <p>Most likely, it is through <code>auto-inserted aresample</code>. Try to understand

  539. why the converting filter was needed at that place.

  540. </p>

  541. <p>Just before the output is a likely place, as <samp>-f lavfi</samp> currently

  542. only support packed S16.

  543. </p>

  544. <p>Then insert the correct <code>aformat</code> explicitly in the filtergraph,

  545. specifying the exact format.

  546. </p>

  547. <div class="example">

  548. <pre class="example">aformat=sample_fmts=s16:channel_layouts=stereo

  549. </pre></div>

  550. 

  551. <a name="Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f"></a>

  552. <h3 class="section">3.16 Why does FFmpeg not see the subtitles in my VOB file?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f" aria-hidden="true">TOC</a></span></h3>

  553. 

  554. <p>VOB and a few other formats do not have a global header that describes

  555. everything present in the file. Instead, applications are supposed to scan

  556. the file to see what it contains. Since VOB files are frequently large, only

  557. the beginning is scanned. If the subtitles happen only later in the file,

  558. they will not be initially detected.

  559. </p>

  560. <p>Some applications, including the <code>ffmpeg</code> command-line tool, can only

  561. work with streams that were detected during the initial scan; streams that

  562. are detected later are ignored.

  563. </p>

  564. <p>The size of the initial scan is controlled by two options: <code>probesize</code>

  565. (default ~5 Mo) and <code>analyzeduration</code> (default 5,000,000 µs = 5 s). For

  566. the subtitle stream to be detected, both values must be large enough.

  567. </p>

  568. <a name="Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f"></a>

  569. <h3 class="section">3.17 Why was the <code>ffmpeg</code> <samp>-sameq</samp> option removed? What to use instead?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f" aria-hidden="true">TOC</a></span></h3>

  570. 

  571. <p>The <samp>-sameq</samp> option meant &quot;same quantizer&quot;, and made sense only in a

  572. very limited set of cases. Unfortunately, a lot of people mistook it for

  573. &quot;same quality&quot; and used it in places where it did not make sense: it had

  574. roughly the expected visible effect, but achieved it in a very inefficient

  575. way.

  576. </p>

  577. <p>Each encoder has its own set of options to set the quality-vs-size balance,

  578. use the options for the encoder you are using to set the quality level to a

  579. point acceptable for your tastes. The most common options to do that are

  580. <samp>-qscale</samp> and <samp>-qmax</samp>, but you should peruse the documentation

  581. of the encoder you chose.

  582. </p>

  583. <a name="I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f"></a>

  584. <h3 class="section">3.18 I have a stretched video, why does scaling does not fix it?<span class="pull-right"><a class="anchor hidden-xs" href="#I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f" aria-hidden="true">TOC</a></span></h3>

  585. 

  586. <p>A lot of video codecs and formats can store the <em>aspect ratio</em> of the

  587. video: this is the ratio between the width and the height of either the full

  588. image (DAR, display aspect ratio) or individual pixels (SAR, sample aspect

  589. ratio). For example, EGA screens at resolution 640×350 had 4:3 DAR and 35:48

  590. SAR.

  591. </p>

  592. <p>Most still image processing work with square pixels, i.e. 1:1 SAR, but a lot

  593. of video standards, especially from the analogic-numeric transition era, use

  594. non-square pixels.

  595. </p>

  596. <p>Most processing filters in FFmpeg handle the aspect ratio to avoid

  597. stretching the image: cropping adjusts the DAR to keep the SAR constant,

  598. scaling adjusts the SAR to keep the DAR constant.

  599. </p>

  600. <p>If you want to stretch, or “unstretch”, the image, you need to override the

  601. information with the

  602. <a href="ffmpeg-filters.html#setdar_002c-setsar"><code>setdar or setsar filters</code></a>.

  603. </p>

  604. <p>Do not forget to examine carefully the original video to check whether the

  605. stretching comes from the image or from the aspect ratio information.

  606. </p>

  607. <p>For example, to fix a badly encoded EGA capture, use the following commands,

  608. either the first one to upscale to square pixels or the second one to set

  609. the correct aspect ratio or the third one to avoid transcoding (may not work

  610. depending on the format / codec / player / phase of the moon):

  611. </p>

  612. <div class="example">

  613. <pre class="example">ffmpeg -i ega_screen.nut -vf scale=640:480,setsar=1 ega_screen_scaled.nut

  614. ffmpeg -i ega_screen.nut -vf setdar=4/3 ega_screen_anamorphic.nut

  615. ffmpeg -i ega_screen.nut -aspect 4/3 -c copy ega_screen_overridden.nut

  616. </pre></div>

  617. 

  618. <span id="background-task"></span><a name="How-do-I-run-ffmpeg-as-a-background-task_003f"></a>

  619. <h3 class="section">3.19 How do I run ffmpeg as a background task?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-run-ffmpeg-as-a-background-task_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-run-ffmpeg-as-a-background-task_003f" aria-hidden="true">TOC</a></span></h3>

  620. 

  621. <p>ffmpeg normally checks the console input, for entries like &quot;q&quot; to stop

  622. and &quot;?&quot; to give help, while performing operations. ffmpeg does not have a way of

  623. detecting when it is running as a background task.

  624. When it checks the console input, that can cause the process running ffmpeg

  625. in the background to suspend.

  626. </p>

  627. <p>To prevent those input checks, allowing ffmpeg to run as a background task,

  628. use the <a href="ffmpeg.html#stdin-option"><code>-nostdin</code> option</a>

  629. in the ffmpeg invocation. This is effective whether you run ffmpeg in a shell

  630. or invoke ffmpeg in its own process via an operating system API.

  631. </p>

  632. <p>As an alternative, when you are running ffmpeg in a shell, you can redirect

  633. standard input to <code>/dev/null</code> (on Linux and macOS)

  634. or <code>NUL</code> (on Windows). You can do this redirect either

  635. on the ffmpeg invocation, or from a shell script which calls ffmpeg.

  636. </p>

  637. <p>For example:

  638. </p>

  639. <div class="example">

  640. <pre class="example">ffmpeg -nostdin -i INPUT OUTPUT

  641. </pre></div>

  642. 

  643. <p>or (on Linux, macOS, and other UNIX-like shells):

  644. </p>

  645. <div class="example">

  646. <pre class="example">ffmpeg -i INPUT OUTPUT &lt;/dev/null

  647. </pre></div>

  648. 

  649. <p>or (on Windows):

  650. </p>

  651. <div class="example">

  652. <pre class="example">ffmpeg -i INPUT OUTPUT &lt;NUL

  653. </pre></div>

  654. 

  655. <a name="How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f"></a>

  656. <h3 class="section">3.20 How do I prevent ffmpeg from suspending with a message like <em>suspended (tty output)</em>?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f" aria-hidden="true">TOC</a></span></h3>

  657. 

  658. <p>If you run ffmpeg in the background, you may find that its process suspends.

  659. There may be a message like <em>suspended (tty output)</em>. The question is how

  660. to prevent the process from being suspended.

  661. </p>

  662. <p>For example:

  663. </p>

  664. <div class="example">

  665. <pre class="example">% ffmpeg -i INPUT OUTPUT &amp;&gt; ~/tmp/log.txt &amp;

  666. [1] 93352

  667. %

  668. [1]  + suspended (tty output)  ffmpeg -i INPUT OUTPUT &amp;&gt;

  669. </pre></div>

  670. 

  671. <p>The message &quot;tty output&quot; notwithstanding, the problem here is that

  672. ffmpeg normally checks the console input when it runs. The operating system

  673. detects this, and suspends the process until you can bring it to the

  674. foreground and attend to it.

  675. </p>

  676. <p>The solution is to use the right techniques to tell ffmpeg not to consult

  677. console input. You can use the

  678. <a href="ffmpeg.html#stdin-option"><code>-nostdin</code> option</a>,

  679. or redirect standard input with <code>&lt; /dev/null</code>.

  680. See FAQ

  681. <a href="#background-task"><em>How do I run ffmpeg as a background task?</em></a>

  682. for details.

  683. </p>

  684. <a name="Development"></a>

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

  686. 

  687. <a name="Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f"></a>

  688. <h3 class="section">4.1 Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat?<span class="pull-right"><a class="anchor hidden-xs" href="#Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f" aria-hidden="true">TOC</a></span></h3>

  689. 

  690. <p>Yes. Check the <samp>doc/examples</samp> directory in the source

  691. repository, also available online at:

  692. <a href="https://github.com/FFmpeg/FFmpeg/tree/master/doc/examples">https://github.com/FFmpeg/FFmpeg/tree/master/doc/examples</a>.

  693. </p>

  694. <p>Examples are also installed by default, usually in

  695. <code>$PREFIX/share/ffmpeg/examples</code>.

  696. </p>

  697. <p>Also you may read the Developers Guide of the FFmpeg documentation. Alternatively,

  698. examine the source code for one of the many open source projects that

  699. already incorporate FFmpeg at (<a href="projects.html">projects.html</a>).

  700. </p>

  701. <a name="Can-you-support-my-C-compiler-XXX_003f"></a>

  702. <h3 class="section">4.2 Can you support my C compiler XXX?<span class="pull-right"><a class="anchor hidden-xs" href="#Can-you-support-my-C-compiler-XXX_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Can-you-support-my-C-compiler-XXX_003f" aria-hidden="true">TOC</a></span></h3>

  703. 

  704. <p>It depends. If your compiler is C99-compliant, then patches to support

  705. it are likely to be welcome if they do not pollute the source code

  706. with <code>#ifdef</code>s related to the compiler.

  707. </p>

  708. <a name="Is-Microsoft-Visual-C_002b_002b-supported_003f"></a>

  709. <h3 class="section">4.3 Is Microsoft Visual C++ supported?<span class="pull-right"><a class="anchor hidden-xs" href="#Is-Microsoft-Visual-C_002b_002b-supported_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Is-Microsoft-Visual-C_002b_002b-supported_003f" aria-hidden="true">TOC</a></span></h3>

  710. 

  711. <p>Yes. Please see the <a href="platform.html">Microsoft Visual C++</a>

  712. section in the FFmpeg documentation.

  713. </p>

  714. <a name="Can-you-add-automake_002c-libtool-or-autoconf-support_003f"></a>

  715. <h3 class="section">4.4 Can you add automake, libtool or autoconf support?<span class="pull-right"><a class="anchor hidden-xs" href="#Can-you-add-automake_002c-libtool-or-autoconf-support_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Can-you-add-automake_002c-libtool-or-autoconf-support_003f" aria-hidden="true">TOC</a></span></h3>

  716. 

  717. <p>No. These tools are too bloated and they complicate the build.

  718. </p>

  719. <a name="Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f"></a>

  720. <h3 class="section">4.5 Why not rewrite FFmpeg in object-oriented C++?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f" aria-hidden="true">TOC</a></span></h3>

  721. 

  722. <p>FFmpeg is already organized in a highly modular manner and does not need to

  723. be rewritten in a formal object language. Further, many of the developers

  724. favor straight C; it works for them. For more arguments on this matter,

  725. read <a href="https://web.archive.org/web/20111004021423/http://kernel.org/pub/linux/docs/lkml/#s15">&quot;Programming Religion&quot;</a>.

  726. </p>

  727. <a name="Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f"></a>

  728. <h3 class="section">4.6 Why are the ffmpeg programs devoid of debugging symbols?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f" aria-hidden="true">TOC</a></span></h3>

  729. 

  730. <p>The build process creates <code>ffmpeg_g</code>, <code>ffplay_g</code>, etc. which

  731. contain full debug information. Those binaries are stripped to create

  732. <code>ffmpeg</code>, <code>ffplay</code>, etc. If you need the debug information, use

  733. the *_g versions.

  734. </p>

  735. <a name="I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f"></a>

  736. <h3 class="section">4.7 I do not like the LGPL, can I contribute code under the GPL instead?<span class="pull-right"><a class="anchor hidden-xs" href="#I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f" aria-hidden="true">TOC</a></span></h3>

  737. 

  738. <p>Yes, as long as the code is optional and can easily and cleanly be placed

  739. under #if CONFIG_GPL without breaking anything. So, for example, a new codec

  740. or filter would be OK under GPL while a bug fix to LGPL code would not.

  741. </p>

  742. <a name="I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e"></a>

  743. <h3 class="section">4.8 I&rsquo;m using FFmpeg from within my C application but the linker complains about missing symbols from the libraries themselves.<span class="pull-right"><a class="anchor hidden-xs" href="#I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e" aria-hidden="true">TOC</a></span></h3>

  744. 

  745. <p>FFmpeg builds static libraries by default. In static libraries, dependencies

  746. are not handled. That has two consequences. First, you must specify the

  747. libraries in dependency order: <code>-lavdevice</code> must come before

  748. <code>-lavformat</code>, <code>-lavutil</code> must come after everything else, etc.

  749. Second, external libraries that are used in FFmpeg have to be specified too.

  750. </p>

  751. <p>An easy way to get the full list of required libraries in dependency order

  752. is to use <code>pkg-config</code>.

  753. </p>

  754. <div class="example">

  755. <pre class="example">c99 -o program program.c $(pkg-config --cflags --libs libavformat libavcodec)

  756. </pre></div>

  757. 

  758. <p>See <samp>doc/example/Makefile</samp> and <samp>doc/example/pc-uninstalled</samp> for

  759. more details.

  760. </p>

  761. <a name="I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e"></a>

  762. <h3 class="section">4.9 I&rsquo;m using FFmpeg from within my C++ application but the linker complains about missing symbols which seem to be available.<span class="pull-right"><a class="anchor hidden-xs" href="#I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e" aria-hidden="true">TOC</a></span></h3>

  763. 

  764. <p>FFmpeg is a pure C project, so to use the libraries within your C++ application

  765. you need to explicitly state that you are using a C library. You can do this by

  766. encompassing your FFmpeg includes using <code>extern &quot;C&quot;</code>.

  767. </p>

  768. <p>See <a href="http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html#faq-32.3">http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html#faq-32.3</a>

  769. </p>

  770. <a name="I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope"></a>

  771. <h3 class="section">4.10 I&rsquo;m using libavutil from within my C++ application but the compiler complains about &rsquo;UINT64_C&rsquo; was not declared in this scope<span class="pull-right"><a class="anchor hidden-xs" href="#I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope" aria-hidden="true">TOC</a></span></h3>

  772. 

  773. <p>FFmpeg is a pure C project using C99 math features, in order to enable C++

  774. to use them you have to append -D__STDC_CONSTANT_MACROS to your CXXFLAGS

  775. </p>

  776. <a name="I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f"></a>

  777. <h3 class="section">4.11 I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat?<span class="pull-right"><a class="anchor hidden-xs" href="#I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f" aria-hidden="true">TOC</a></span></h3>

  778. 

  779. <p>You have to create a custom AVIOContext using <code>avio_alloc_context</code>,

  780. see <samp>libavformat/aviobuf.c</samp> in FFmpeg and <samp>libmpdemux/demux_lavf.c</samp> in MPlayer or MPlayer2 sources.

  781. </p>

  782. <a name="Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f"></a>

  783. <h3 class="section">4.12 Where is the documentation about ffv1, msmpeg4, asv1, 4xm?<span class="pull-right"><a class="anchor hidden-xs" href="#Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f" aria-hidden="true">TOC</a></span></h3>

  784. 

  785. <p>see <a href="https://www.ffmpeg.org/~michael/">https://www.ffmpeg.org/~michael/</a>

  786. </p>

  787. <a name="How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f"></a>

  788. <h3 class="section">4.13 How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f" aria-hidden="true">TOC</a></span></h3>

  789. 

  790. <p>Even if peculiar since it is network oriented, RTP is a container like any

  791. other. You have to <em>demux</em> RTP before feeding the payload to libavcodec.

  792. In this specific case please look at RFC 4629 to see how it should be done.

  793. </p>

  794. <a name="AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e"></a>

  795. <h3 class="section">4.14 AVStream.r_frame_rate is wrong, it is much larger than the frame rate.<span class="pull-right"><a class="anchor hidden-xs" href="#AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e" aria-hidden="true">TOC</a></span></h3>

  796. 

  797. <p><code>r_frame_rate</code> is NOT the average frame rate, it is the smallest frame rate

  798. that can accurately represent all timestamps. So no, it is not

  799. wrong if it is larger than the average!

  800. For example, if you have mixed 25 and 30 fps content, then <code>r_frame_rate</code>

  801. will be 150 (it is the least common multiple).

  802. If you are looking for the average frame rate, see <code>AVStream.avg_frame_rate</code>.

  803. </p>

  804. <a name="Why-is-make-fate-not-running-all-tests_003f"></a>

  805. <h3 class="section">4.15 Why is <code>make fate</code> not running all tests?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-is-make-fate-not-running-all-tests_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-is-make-fate-not-running-all-tests_003f" aria-hidden="true">TOC</a></span></h3>

  806. 

  807. <p>Make sure you have the fate-suite samples and the <code>SAMPLES</code> Make variable

  808. or <code>FATE_SAMPLES</code> environment variable or the <code>--samples</code>

  809. <code>configure</code> option is set to the right path.

  810. </p>

  811. <a name="Why-is-make-fate-not-finding-the-samples_003f"></a>

  812. <h3 class="section">4.16 Why is <code>make fate</code> not finding the samples?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-is-make-fate-not-finding-the-samples_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-is-make-fate-not-finding-the-samples_003f" aria-hidden="true">TOC</a></span></h3>

  813. 

  814. <p>Do you happen to have a <code>~</code> character in the samples path to indicate a

  815. home directory? The value is used in ways where the shell cannot expand it,

  816. causing FATE to not find files. Just replace <code>~</code> by the full path.

  817. </p>

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

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

  820.       </p>

  821.     </div>

  822.   </body>

  823. </html>