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  13 <title>FFmpeg FAQ</title>
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  45 <h1 class="settitle">FFmpeg FAQ</h1>
  46
  47 <a name="SEC_Contents"></a>
  48 <h1>Table of Contents</h1>
  49 <div class="contents">
  50
  51 <ul class="toc">
  52   <li><a name="toc-General-Questions" href="#General-Questions">1. General Questions</a>
  53   <ul class="toc">
  54     <li><a name="toc-When-will-the-next-FFmpeg-version-be-released_003f-_002f-Why-are-FFmpeg-releases-so-few-and-far-between_003f" href="#When-will-the-next-FFmpeg-version-be-released_003f-_002f-Why-are-FFmpeg-releases-so-few-and-far-between_003f">1.1 When will the next FFmpeg version be released? / Why are FFmpeg releases so few and far between?</a></li>
  55     <li><a name="toc-I-have-a-problem-with-an-old-version-of-FFmpeg_003b-where-should-I-report-it_003f" href="#I-have-a-problem-with-an-old-version-of-FFmpeg_003b-where-should-I-report-it_003f">1.2 I have a problem with an old version of FFmpeg; where should I report it?</a></li>
  56     <li><a name="toc-Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f" href="#Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f">1.3 Why doesn&rsquo;t FFmpeg support feature [xyz]?</a></li>
  57     <li><a name="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">1.4 FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it?</a></li>
  58     <li><a name="toc-My-bug-report_002fmail-to-ffmpeg_002ddevel_002fuser-has-not-received-any-replies_002e" href="#My-bug-report_002fmail-to-ffmpeg_002ddevel_002fuser-has-not-received-any-replies_002e">1.5 My bug report/mail to ffmpeg-devel/user has not received any replies.</a></li>
  59     <li><a name="toc-Is-there-a-forum-for-FFmpeg_003f-I-do-not-like-mailing-lists_002e" href="#Is-there-a-forum-for-FFmpeg_003f-I-do-not-like-mailing-lists_002e">1.6 Is there a forum for FFmpeg? I do not like mailing lists.</a></li>
  60     <li><a name="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">1.7 I cannot read this file although this format seems to be supported by ffmpeg.</a></li>
  61     <li><a name="toc-Which-codecs-are-supported-by-Windows_003f" href="#Which-codecs-are-supported-by-Windows_003f">1.8 Which codecs are supported by Windows?</a></li>
  62   </ul></li>
  63   <li><a name="toc-Compilation" href="#Compilation">2. Compilation</a>
  64   <ul class="toc">
  65     <li><a name="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>
  66   </ul></li>
  67   <li><a name="toc-Usage" href="#Usage">3. Usage</a>
  68   <ul class="toc">
  69     <li><a name="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>
  70     <li><a name="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>
  71     <li><a name="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>
  72     <li><a name="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>
  73     <li><a name="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>
  74     <li><a name="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>
  75     <li><a name="toc-Why-can-I-not-change-the-framerate_003f" href="#Why-can-I-not-change-the-framerate_003f">3.7 Why can I not change the framerate?</a></li>
  76     <li><a name="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>
  77     <li><a name="toc-How-do-I-encode-videos-which-play-on-the-iPod_003f" href="#How-do-I-encode-videos-which-play-on-the-iPod_003f">3.9 How do I encode videos which play on the iPod?</a></li>
  78     <li><a name="toc-How-do-I-encode-videos-which-play-on-the-PSP_003f" href="#How-do-I-encode-videos-which-play-on-the-PSP_003f">3.10 How do I encode videos which play on the PSP?</a></li>
  79     <li><a name="toc-Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f" href="#Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f">3.11 Which are good parameters for encoding high quality MPEG-4?</a></li>
  80     <li><a name="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">3.12 Which are good parameters for encoding high quality MPEG-1/MPEG-2?</a></li>
  81     <li><a name="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">3.13 Interlaced video looks very bad when encoded with ffmpeg, what is wrong?</a></li>
  82     <li><a name="toc-How-can-I-read-DirectShow-files_003f" href="#How-can-I-read-DirectShow-files_003f">3.14 How can I read DirectShow files?</a></li>
  83     <li><a name="toc-How-can-I-join-video-files_003f" href="#How-can-I-join-video-files_003f">3.15 How can I join video files?</a></li>
  84     <li><a name="toc-The-ffmpeg-program-does-not-respect-the-_002dmaxrate-setting_002c-some-frames-are-bigger-than-maxrate_002ffps_002e" href="#The-ffmpeg-program-does-not-respect-the-_002dmaxrate-setting_002c-some-frames-are-bigger-than-maxrate_002ffps_002e">3.16 The ffmpeg program does not respect the -maxrate setting, some frames are bigger than maxrate/fps.</a></li>
  85     <li><a name="toc-I-want-CBR_002c-but-no-matter-what-I-do-frame-sizes-differ_002e" href="#I-want-CBR_002c-but-no-matter-what-I-do-frame-sizes-differ_002e">3.17 I want CBR, but no matter what I do frame sizes differ.</a></li>
  86     <li><a name="toc-How-do-I-check-if-a-stream-is-CBR_003f" href="#How-do-I-check-if-a-stream-is-CBR_003f">3.18 How do I check if a stream is CBR?</a></li>
  87   </ul></li>
  88   <li><a name="toc-Development" href="#Development">4. Development</a>
  89   <ul class="toc">
  90     <li><a name="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>
  91     <li><a name="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>
  92     <li><a name="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>
  93     <li><a name="toc-Can-I-use-FFmpeg-or-libavcodec-under-Windows_003f" href="#Can-I-use-FFmpeg-or-libavcodec-under-Windows_003f">4.4 Can I use FFmpeg or libavcodec under Windows?</a></li>
  94     <li><a name="toc-Can-you-add-automake_002c-libtool-or-autoconf-support_003f" href="#Can-you-add-automake_002c-libtool-or-autoconf-support_003f">4.5 Can you add automake, libtool or autoconf support?</a></li>
  95     <li><a name="toc-Why-not-rewrite-ffmpeg-in-object_002doriented-C_002b_002b_003f" href="#Why-not-rewrite-ffmpeg-in-object_002doriented-C_002b_002b_003f">4.6 Why not rewrite ffmpeg in object-oriented C++?</a></li>
  96     <li><a name="toc-Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f" href="#Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f">4.7 Why are the ffmpeg programs devoid of debugging symbols?</a></li>
  97     <li><a name="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">4.8 I do not like the LGPL, can I contribute code under the GPL instead?</a></li>
  98     <li><a name="toc-I-want-to-compile-xyz_002ec-alone-but-my-compiler-produced-many-errors_002e" href="#I-want-to-compile-xyz_002ec-alone-but-my-compiler-produced-many-errors_002e">4.9 I want to compile xyz.c alone but my compiler produced many errors.</a></li>
  99     <li><a name="toc-I_0027m-using-libavcodec-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e" href="#I_0027m-using-libavcodec-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e">4.10 I&rsquo;m using libavcodec from within my C++ application but the linker complains about missing symbols which seem to be available.</a></li>
 100     <li><a name="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>
 101     <li><a name="toc-I-get-_0022No-compatible-shell-script-interpreter-found_002e_0022-in-MSys_002e" href="#I-get-_0022No-compatible-shell-script-interpreter-found_002e_0022-in-MSys_002e">4.12 I get &quot;No compatible shell script interpreter found.&quot; in MSys.</a></li>
 102     <li><a name="toc-I-get-_0022_002e_002fconfigure_003a-line-_003cxxx_003e_003a-pr_003a-command-not-found_0022-in-MSys_002e" href="#I-get-_0022_002e_002fconfigure_003a-line-_003cxxx_003e_003a-pr_003a-command-not-found_0022-in-MSys_002e">4.13 I get &quot;./configure: line &lt;xxx&gt;: pr: command not found&quot; in MSys.</a></li>
 103     <li><a name="toc-Where-can-I-find-libav_002a-headers-for-Pascal_002fDelphi_003f" href="#Where-can-I-find-libav_002a-headers-for-Pascal_002fDelphi_003f">4.14 Where can I find libav* headers for Pascal/Delphi?</a></li>
 104     <li><a name="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">4.15 Where is the documentation about ffv1, msmpeg4, asv1, 4xm?</a></li>
 105     <li><a name="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">4.16 How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?</a></li>
 106     <li><a name="toc-AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-framerate_002e" href="#AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-framerate_002e">4.17 AVStream.r_frame_rate is wrong, it is much larger than the framerate.</a></li>
 107   </ul>
 108 </li>
 109 </ul>
 110 </div>
 111
 112 <hr size="1">
 113 <a name="General-Questions"></a>
 114 <h1 class="chapter"><a href="faq.html#toc-General-Questions">1. General Questions</a></h1>
 115
 116 <a name="When-will-the-next-FFmpeg-version-be-released_003f-_002f-Why-are-FFmpeg-releases-so-few-and-far-between_003f"></a>
 117 <h2 class="section"><a href="faq.html#toc-When-will-the-next-FFmpeg-version-be-released_003f-_002f-Why-are-FFmpeg-releases-so-few-and-far-between_003f">1.1 When will the next FFmpeg version be released? / Why are FFmpeg releases so few and far between?</a></h2>
 118
 119 <p>Like most open source projects FFmpeg suffers from a certain lack of
 120 manpower. For this reason the developers have to prioritize the work
 121 they do and putting out releases is not at the top of the list, fixing
 122 bugs and reviewing patches takes precedence. Please don&rsquo;t complain or
 123 request more timely and/or frequent releases unless you are willing to
 124 help out creating them.
 125 </p>
 126 <a name="I-have-a-problem-with-an-old-version-of-FFmpeg_003b-where-should-I-report-it_003f"></a>
 127 <h2 class="section"><a href="faq.html#toc-I-have-a-problem-with-an-old-version-of-FFmpeg_003b-where-should-I-report-it_003f">1.2 I have a problem with an old version of FFmpeg; where should I report it?</a></h2>
 128 <p>Nowhere. We do not support old FFmpeg versions in any way, we simply lack
 129 the time, motivation and manpower to do so. If you have a problem with an
 130 old version of FFmpeg, upgrade to the latest git snapshot. If you
 131 still experience the problem, then you can report it according to the
 132 guidelines in <a href="http://ffmpeg.org/bugreports.html">http://ffmpeg.org/bugreports.html</a>.
 133 </p>
 134 <a name="Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f"></a>
 135 <h2 class="section"><a href="faq.html#toc-Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f">1.3 Why doesn&rsquo;t FFmpeg support feature [xyz]?</a></h2>
 136
 137 <p>Because no one has taken on that task yet. FFmpeg development is
 138 driven by the tasks that are important to the individual developers.
 139 If there is a feature that is important to you, the best way to get
 140 it implemented is to undertake the task yourself or sponsor a developer.
 141 </p>
 142 <a name="FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f"></a>
 143 <h2 class="section"><a href="faq.html#toc-FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f">1.4 FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it?</a></h2>
 144
 145 <p>No. Windows DLLs are not portable, bloated and often slow.
 146 Moreover FFmpeg strives to support all codecs natively.
 147 A DLL loader is not conducive to that goal.
 148 </p>
 149 <a name="My-bug-report_002fmail-to-ffmpeg_002ddevel_002fuser-has-not-received-any-replies_002e"></a>
 150 <h2 class="section"><a href="faq.html#toc-My-bug-report_002fmail-to-ffmpeg_002ddevel_002fuser-has-not-received-any-replies_002e">1.5 My bug report/mail to ffmpeg-devel/user has not received any replies.</a></h2>
 151
 152 <p>Likely reasons
 153 </p><ul>
 154 <li> We are busy and haven&rsquo;t had time yet to read your report or
 155 investigate the issue.
 156 </li><li> You didn&rsquo;t follow <a href="http://ffmpeg.org/bugreports.html">http://ffmpeg.org/bugreports.html</a>.
 157 </li><li> You didn&rsquo;t use git master.
 158 </li><li> You reported a segmentation fault without gdb output.
 159 </li><li> You describe a problem but not how to reproduce it.
 160 </li><li> It&rsquo;s unclear if you use ffmpeg as command line tool or use
 161 libav* from another application.
 162 </li><li> You speak about a video having problems on playback but
 163 not what you use to play it.
 164 </li><li> We have no faint clue what you are talking about besides
 165 that it is related to FFmpeg.
 166 </li></ul>
 167
 168 <a name="Is-there-a-forum-for-FFmpeg_003f-I-do-not-like-mailing-lists_002e"></a>
 169 <h2 class="section"><a href="faq.html#toc-Is-there-a-forum-for-FFmpeg_003f-I-do-not-like-mailing-lists_002e">1.6 Is there a forum for FFmpeg? I do not like mailing lists.</a></h2>
 170
 171 <p>You may view our mailing lists with a more forum-alike look here:
 172 <a href="http://dir.gmane.org/gmane.comp.video.ffmpeg.user">http://dir.gmane.org/gmane.comp.video.ffmpeg.user</a>,
 173 but, if you post, please remember that our mailing list rules still apply there.
 174 </p>
 175 <a name="I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e"></a>
 176 <h2 class="section"><a href="faq.html#toc-I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e">1.7 I cannot read this file although this format seems to be supported by ffmpeg.</a></h2>
 177
 178 <p>Even if ffmpeg can read the container format, it may not support all its
 179 codecs. Please consult the supported codec list in the ffmpeg
 180 documentation.
 181 </p>
 182 <a name="Which-codecs-are-supported-by-Windows_003f"></a>
 183 <h2 class="section"><a href="faq.html#toc-Which-codecs-are-supported-by-Windows_003f">1.8 Which codecs are supported by Windows?</a></h2>
 184
 185 <p>Windows does not support standard formats like MPEG very well, unless you
 186 install some additional codecs.
 187 </p>
 188 <p>The following list of video codecs should work on most Windows systems:
 189 </p><dl compact="compact">
 190 <dt> &lsquo;<samp>msmpeg4v2</samp>&rsquo;</dt>
 191 <dd><p>.avi/.asf
 192 </p></dd>
 193 <dt> &lsquo;<samp>msmpeg4</samp>&rsquo;</dt>
 194 <dd><p>.asf only
 195 </p></dd>
 196 <dt> &lsquo;<samp>wmv1</samp>&rsquo;</dt>
 197 <dd><p>.asf only
 198 </p></dd>
 199 <dt> &lsquo;<samp>wmv2</samp>&rsquo;</dt>
 200 <dd><p>.asf only
 201 </p></dd>
 202 <dt> &lsquo;<samp>mpeg4</samp>&rsquo;</dt>
 203 <dd><p>Only if you have some MPEG-4 codec like ffdshow or Xvid installed.
 204 </p></dd>
 205 <dt> &lsquo;<samp>mpeg1video</samp>&rsquo;</dt>
 206 <dd><p>.mpg only
 207 </p></dd>
 208 </dl>
 209 <p>Note, ASF files often have .wmv or .wma extensions in Windows. It should also
 210 be mentioned that Microsoft claims a patent on the ASF format, and may sue
 211 or threaten users who create ASF files with non-Microsoft software. It is
 212 strongly advised to avoid ASF where possible.
 213 </p>
 214 <p>The following list of audio codecs should work on most Windows systems:
 215 </p><dl compact="compact">
 216 <dt> &lsquo;<samp>adpcm_ima_wav</samp>&rsquo;</dt>
 217 <dt> &lsquo;<samp>adpcm_ms</samp>&rsquo;</dt>
 218 <dt> &lsquo;<samp>pcm_s16le</samp>&rsquo;</dt>
 219 <dd><p>always
 220 </p></dd>
 221 <dt> &lsquo;<samp>libmp3lame</samp>&rsquo;</dt>
 222 <dd><p>If some MP3 codec like LAME is installed.
 223 </p></dd>
 224 </dl>
 225
 226
 227 <a name="Compilation"></a>
 228 <h1 class="chapter"><a href="faq.html#toc-Compilation">2. Compilation</a></h1>
 229
 230 <a name="error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027"></a>
 231 <h2 class="section"><a href="faq.html#toc-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></h2>
 232
 233 <p>This is a bug in gcc. Do not report it to us. Instead, please report it to
 234 the gcc developers. Note that we will not add workarounds for gcc bugs.
 235 </p>
 236 <p>Also note that (some of) the gcc developers believe this is not a bug or
 237 not a bug they should fix:
 238 <a href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203">http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203</a>.
 239 Then again, some of them do not know the difference between an undecidable
 240 problem and an NP-hard problem...
 241 </p>
 242 <a name="Usage"></a>
 243 <h1 class="chapter"><a href="faq.html#toc-Usage">3. Usage</a></h1>
 244
 245 <a name="ffmpeg-does-not-work_003b-what-is-wrong_003f"></a>
 246 <h2 class="section"><a href="faq.html#toc-ffmpeg-does-not-work_003b-what-is-wrong_003f">3.1 ffmpeg does not work; what is wrong?</a></h2>
 247
 248 <p>Try a <code>make distclean</code> in the ffmpeg source directory before the build.
 249 If this does not help see
 250 (<a href="http://ffmpeg.org/bugreports.html">http://ffmpeg.org/bugreports.html</a>).
 251 </p>
 252 <a name="How-do-I-encode-single-pictures-into-movies_003f"></a>
 253 <h2 class="section"><a href="faq.html#toc-How-do-I-encode-single-pictures-into-movies_003f">3.2 How do I encode single pictures into movies?</a></h2>
 254
 255 <p>First, rename your pictures to follow a numerical sequence.
 256 For example, img1.jpg, img2.jpg, img3.jpg,...
 257 Then you may run:
 258 </p>
 259 <table><tr><td>&nbsp;</td><td><pre class="example">  ffmpeg -f image2 -i img%d.jpg /tmp/a.mpg
 260 </pre></td></tr></table>
 261
 262 <p>Notice that &lsquo;<samp>%d</samp>&rsquo; is replaced by the image number.
 263 </p>
 264 <p>&lsquo;<tt>img%03d.jpg</tt>&rsquo; means the sequence &lsquo;<tt>img001.jpg</tt>&rsquo;, &lsquo;<tt>img002.jpg</tt>&rsquo;, etc...
 265 </p>
 266 <p>If you have large number of pictures to rename, you can use the
 267 following command to ease the burden. The command, using the bourne
 268 shell syntax, symbolically links all files in the current directory
 269 that match <code>*jpg</code> to the &lsquo;<tt>/tmp</tt>&rsquo; directory in the sequence of
 270 &lsquo;<tt>img001.jpg</tt>&rsquo;, &lsquo;<tt>img002.jpg</tt>&rsquo; and so on.
 271 </p>
 272 <table><tr><td>&nbsp;</td><td><pre class="example">  x=1; for i in *jpg; do counter=$(printf %03d $x); ln -s &quot;$i&quot; /tmp/img&quot;$counter&quot;.jpg; x=$(($x+1)); done
 273 </pre></td></tr></table>
 274
 275 <p>If you want to sequence them by oldest modified first, substitute
 276 <code>$(ls -r -t *jpg)</code> in place of <code>*jpg</code>.
 277 </p>
 278 <p>Then run:
 279 </p>
 280 <table><tr><td>&nbsp;</td><td><pre class="example">  ffmpeg -f image2 -i /tmp/img%03d.jpg /tmp/a.mpg
 281 </pre></td></tr></table>
 282
 283 <p>The same logic is used for any image format that ffmpeg reads.
 284 </p>
 285 <a name="How-do-I-encode-movie-to-single-pictures_003f"></a>
 286 <h2 class="section"><a href="faq.html#toc-How-do-I-encode-movie-to-single-pictures_003f">3.3 How do I encode movie to single pictures?</a></h2>
 287
 288 <p>Use:
 289 </p>
 290 <table><tr><td>&nbsp;</td><td><pre class="example">  ffmpeg -i movie.mpg movie%d.jpg
 291 </pre></td></tr></table>
 292
 293 <p>The &lsquo;<tt>movie.mpg</tt>&rsquo; used as input will be converted to
 294 &lsquo;<tt>movie1.jpg</tt>&rsquo;, &lsquo;<tt>movie2.jpg</tt>&rsquo;, etc...
 295 </p>
 296 <p>Instead of relying on file format self-recognition, you may also use
 297 </p><dl compact="compact">
 298 <dt> &lsquo;<samp>-vcodec ppm</samp>&rsquo;</dt>
 299 <dt> &lsquo;<samp>-vcodec png</samp>&rsquo;</dt>
 300 <dt> &lsquo;<samp>-vcodec mjpeg</samp>&rsquo;</dt>
 301 </dl>
 302 <p>to force the encoding.
 303 </p>
 304 <p>Applying that to the previous example:
 305 </p><table><tr><td>&nbsp;</td><td><pre class="example">  ffmpeg -i movie.mpg -f image2 -vcodec mjpeg menu%d.jpg
 306 </pre></td></tr></table>
 307
 308 <p>Beware that there is no &quot;jpeg&quot; codec. Use &quot;mjpeg&quot; instead.
 309 </p>
 310 <a name="Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f"></a>
 311 <h2 class="section"><a href="faq.html#toc-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></h2>
 312
 313 <p>For multithreaded MPEG* encoding, the encoded slices must be independent,
 314 otherwise thread n would practically have to wait for n-1 to finish, so it&rsquo;s
 315 quite logical that there is a small reduction of quality. This is not a bug.
 316 </p>
 317 <a name="How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f"></a>
 318 <h2 class="section"><a href="faq.html#toc-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></h2>
 319
 320 <p>Use &lsquo;<tt>-</tt>&rsquo; as file name.
 321 </p>
 322 <a name="g_t_002df-jpeg-doesn_0027t-work_002e"></a>
 323 <h2 class="section"><a href="faq.html#toc-_002df-jpeg-doesn_0027t-work_002e">3.6 -f jpeg doesn&rsquo;t work.</a></h2>
 324
 325 <p>Try &rsquo;-f image2 test%d.jpg&rsquo;.
 326 </p>
 327 <a name="Why-can-I-not-change-the-framerate_003f"></a>
 328 <h2 class="section"><a href="faq.html#toc-Why-can-I-not-change-the-framerate_003f">3.7 Why can I not change the framerate?</a></h2>
 329
 330 <p>Some codecs, like MPEG-1/2, only allow a small number of fixed framerates.
 331 Choose a different codec with the -vcodec command line option.
 332 </p>
 333 <a name="How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f"></a>
 334 <h2 class="section"><a href="faq.html#toc-How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f">3.8 How do I encode Xvid or DivX video with ffmpeg?</a></h2>
 335
 336 <p>Both Xvid and DivX (version 4+) are implementations of the ISO MPEG-4
 337 standard (note that there are many other coding formats that use this
 338 same standard). Thus, use &rsquo;-vcodec mpeg4&rsquo; to encode in these formats. The
 339 default fourcc stored in an MPEG-4-coded file will be &rsquo;FMP4&rsquo;. If you want
 340 a different fourcc, use the &rsquo;-vtag&rsquo; option. E.g., &rsquo;-vtag xvid&rsquo; will
 341 force the fourcc &rsquo;xvid&rsquo; to be stored as the video fourcc rather than the
 342 default.
 343 </p>
 344 <a name="How-do-I-encode-videos-which-play-on-the-iPod_003f"></a>
 345 <h2 class="section"><a href="faq.html#toc-How-do-I-encode-videos-which-play-on-the-iPod_003f">3.9 How do I encode videos which play on the iPod?</a></h2>
 346
 347 <dl compact="compact">
 348 <dt> &lsquo;<samp>needed stuff</samp>&rsquo;</dt>
 349 <dd><p>-acodec libfaac -vcodec mpeg4 width&lt;=320 height&lt;=240
 350 </p></dd>
 351 <dt> &lsquo;<samp>working stuff</samp>&rsquo;</dt>
 352 <dd><p>mv4, title
 353 </p></dd>
 354 <dt> &lsquo;<samp>non-working stuff</samp>&rsquo;</dt>
 355 <dd><p>B-frames
 356 </p></dd>
 357 <dt> &lsquo;<samp>example command line</samp>&rsquo;</dt>
 358 <dd><p>ffmpeg -i input -acodec libfaac -ab 128k -vcodec mpeg4 -b 1200k -mbd 2 -flags +mv4+aic -trellis 2 -cmp 2 -subcmp 2 -s 320x180 -metadata title=X output.mp4
 359 </p></dd>
 360 </dl>
 361
 362 <a name="How-do-I-encode-videos-which-play-on-the-PSP_003f"></a>
 363 <h2 class="section"><a href="faq.html#toc-How-do-I-encode-videos-which-play-on-the-PSP_003f">3.10 How do I encode videos which play on the PSP?</a></h2>
 364
 365 <dl compact="compact">
 366 <dt> &lsquo;<samp>needed stuff</samp>&rsquo;</dt>
 367 <dd><p>-acodec libfaac -vcodec mpeg4 width*height&lt;=76800 width%16=0 height%16=0 -ar 24000 -r 30000/1001 or 15000/1001 -f psp
 368 </p></dd>
 369 <dt> &lsquo;<samp>working stuff</samp>&rsquo;</dt>
 370 <dd><p>mv4, title
 371 </p></dd>
 372 <dt> &lsquo;<samp>non-working stuff</samp>&rsquo;</dt>
 373 <dd><p>B-frames
 374 </p></dd>
 375 <dt> &lsquo;<samp>example command line</samp>&rsquo;</dt>
 376 <dd><p>ffmpeg -i input -acodec libfaac -ab 128k -vcodec mpeg4 -b 1200k -ar 24000 -mbd 2 -flags +mv4+aic -trellis 2 -cmp 2 -subcmp 2 -s 368x192 -r 30000/1001 -metadata title=X -f psp output.mp4
 377 </p></dd>
 378 <dt> &lsquo;<samp>needed stuff for H.264</samp>&rsquo;</dt>
 379 <dd><p>-acodec libfaac -vcodec libx264 width*height&lt;=76800 width%16=0? height%16=0? -ar 48000 -coder 1 -r 30000/1001 or 15000/1001 -f psp
 380 </p></dd>
 381 <dt> &lsquo;<samp>working stuff for H.264</samp>&rsquo;</dt>
 382 <dd><p>title, loop filter
 383 </p></dd>
 384 <dt> &lsquo;<samp>non-working stuff for H.264</samp>&rsquo;</dt>
 385 <dd><p>CAVLC
 386 </p></dd>
 387 <dt> &lsquo;<samp>example command line</samp>&rsquo;</dt>
 388 <dd><p>ffmpeg -i input -acodec libfaac -ab 128k -vcodec libx264 -b 1200k -ar 48000 -mbd 2 -coder 1 -cmp 2 -subcmp 2 -s 368x192 -r 30000/1001 -metadata title=X -f psp -flags loop -trellis 2 -partitions parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 output.mp4
 389 </p></dd>
 390 <dt> &lsquo;<samp>higher resolution for newer PSP firmwares, width&lt;=480, height&lt;=272</samp>&rsquo;</dt>
 391 <dd><p>-vcodec libx264 -level 21 -coder 1 -f psp
 392 </p></dd>
 393 <dt> &lsquo;<samp>example command line</samp>&rsquo;</dt>
 394 <dd><p>ffmpeg -i input -acodec libfaac -ab 128k -ac 2 -ar 48000 -vcodec libx264 -level 21 -b 640k -coder 1 -f psp -flags +loop -trellis 2 -partitions +parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 -g 250 -s 480x272 output.mp4
 395 </p></dd>
 396 </dl>
 397
 398 <a name="Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f"></a>
 399 <h2 class="section"><a href="faq.html#toc-Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f">3.11 Which are good parameters for encoding high quality MPEG-4?</a></h2>
 400
 401 <p>&rsquo;-mbd rd -flags +mv4+aic -trellis 2 -cmp 2 -subcmp 2 -g 300 -pass 1/2&rsquo;,
 402 things to try: &rsquo;-bf 2&rsquo;, &rsquo;-flags qprd&rsquo;, &rsquo;-flags mv0&rsquo;, &rsquo;-flags skiprd&rsquo;.
 403 </p>
 404 <a name="Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f"></a>
 405 <h2 class="section"><a href="faq.html#toc-Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f">3.12 Which are good parameters for encoding high quality MPEG-1/MPEG-2?</a></h2>
 406
 407 <p>&rsquo;-mbd rd -trellis 2 -cmp 2 -subcmp 2 -g 100 -pass 1/2&rsquo;
 408 but beware the &rsquo;-g 100&rsquo; might cause problems with some decoders.
 409 Things to try: &rsquo;-bf 2&rsquo;, &rsquo;-flags qprd&rsquo;, &rsquo;-flags mv0&rsquo;, &rsquo;-flags skiprd.
 410 </p>
 411 <a name="Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f"></a>
 412 <h2 class="section"><a href="faq.html#toc-Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f">3.13 Interlaced video looks very bad when encoded with ffmpeg, what is wrong?</a></h2>
 413
 414 <p>You should use &rsquo;-flags +ilme+ildct&rsquo; and maybe &rsquo;-flags +alt&rsquo; for interlaced
 415 material, and try &rsquo;-top 0/1&rsquo; if the result looks really messed-up.
 416 </p>
 417 <a name="How-can-I-read-DirectShow-files_003f"></a>
 418 <h2 class="section"><a href="faq.html#toc-How-can-I-read-DirectShow-files_003f">3.14 How can I read DirectShow files?</a></h2>
 419
 420 <p>If you have built FFmpeg with <code>./configure --enable-avisynth</code>
 421 (only possible on MinGW/Cygwin platforms),
 422 then you may use any file that DirectShow can read as input.
 423 </p>
 424 <p>Just create an &quot;input.avs&quot; text file with this single line ...
 425 </p><table><tr><td>&nbsp;</td><td><pre class="example">  DirectShowSource(&quot;C:\path to your file\yourfile.asf&quot;)
 426 </pre></td></tr></table>
 427 <p>... and then feed that text file to ffmpeg:
 428 </p><table><tr><td>&nbsp;</td><td><pre class="example">  ffmpeg -i input.avs
 429 </pre></td></tr></table>
 430
 431 <p>For ANY other help on Avisynth, please visit the
 432 <a href="http://www.avisynth.org/">Avisynth homepage</a>.
 433 </p>
 434 <a name="How-can-I-join-video-files_003f"></a>
 435 <h2 class="section"><a href="faq.html#toc-How-can-I-join-video-files_003f">3.15 How can I join video files?</a></h2>
 436
 437 <p>A few multimedia containers (MPEG-1, MPEG-2 PS, DV) allow to join video files by
 438 merely concatenating them.
 439 </p>
 440 <p>Hence you may concatenate your multimedia files by first transcoding them to
 441 these privileged formats, then using the humble <code>cat</code> command (or the
 442 equally humble <code>copy</code> under Windows), and finally transcoding back to your
 443 format of choice.
 444 </p>
 445 <table><tr><td>&nbsp;</td><td><pre class="example">ffmpeg -i input1.avi -sameq intermediate1.mpg
 446 ffmpeg -i input2.avi -sameq intermediate2.mpg
 447 cat intermediate1.mpg intermediate2.mpg &gt; intermediate_all.mpg
 448 ffmpeg -i intermediate_all.mpg -sameq output.avi
 449 </pre></td></tr></table>
 450
 451 <p>Notice that you should either use <code>-sameq</code> or set a reasonably high
 452 bitrate for your intermediate and output files, if you want to preserve
 453 video quality.
 454 </p>
 455 <p>Also notice that you may avoid the huge intermediate files by taking advantage
 456 of named pipes, should your platform support it:
 457 </p>
 458 <table><tr><td>&nbsp;</td><td><pre class="example">mkfifo intermediate1.mpg
 459 mkfifo intermediate2.mpg
 460 ffmpeg -i input1.avi -sameq -y intermediate1.mpg &lt; /dev/null &amp;
 461 ffmpeg -i input2.avi -sameq -y intermediate2.mpg &lt; /dev/null &amp;
 462 cat intermediate1.mpg intermediate2.mpg |\
 463 ffmpeg -f mpeg -i - -sameq -vcodec mpeg4 -acodec libmp3lame output.avi
 464 </pre></td></tr></table>
 465
 466 <p>Similarly, the yuv4mpegpipe format, and the raw video, raw audio codecs also
 467 allow concatenation, and the transcoding step is almost lossless.
 468 When using multiple yuv4mpegpipe(s), the first line needs to be discarded
 469 from all but the first stream. This can be accomplished by piping through
 470 <code>tail</code> as seen below. Note that when piping through <code>tail</code> you
 471 must use command grouping, <code>{  ;}</code>, to background properly.
 472 </p>
 473 <p>For example, let&rsquo;s say we want to join two FLV files into an output.flv file:
 474 </p>
 475 <table><tr><td>&nbsp;</td><td><pre class="example">mkfifo temp1.a
 476 mkfifo temp1.v
 477 mkfifo temp2.a
 478 mkfifo temp2.v
 479 mkfifo all.a
 480 mkfifo all.v
 481 ffmpeg -i input1.flv -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 - &gt; temp1.a &lt; /dev/null &amp;
 482 ffmpeg -i input2.flv -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 - &gt; temp2.a &lt; /dev/null &amp;
 483 ffmpeg -i input1.flv -an -f yuv4mpegpipe - &gt; temp1.v &lt; /dev/null &amp;
 484 { ffmpeg -i input2.flv -an -f yuv4mpegpipe - &lt; /dev/null | tail -n +2 &gt; temp2.v ; } &amp;
 485 cat temp1.a temp2.a &gt; all.a &amp;
 486 cat temp1.v temp2.v &gt; all.v &amp;
 487 ffmpeg -f u16le -acodec pcm_s16le -ac 2 -ar 44100 -i all.a \
 488        -f yuv4mpegpipe -i all.v \
 489        -sameq -y output.flv
 490 rm temp[12].[av] all.[av]
 491 </pre></td></tr></table>
 492
 493 <a name="The-ffmpeg-program-does-not-respect-the-_002dmaxrate-setting_002c-some-frames-are-bigger-than-maxrate_002ffps_002e"></a>
 494 <h2 class="section"><a href="faq.html#toc-The-ffmpeg-program-does-not-respect-the-_002dmaxrate-setting_002c-some-frames-are-bigger-than-maxrate_002ffps_002e">3.16 The ffmpeg program does not respect the -maxrate setting, some frames are bigger than maxrate/fps.</a></h2>
 495
 496 <p>Read the MPEG spec about video buffer verifier.
 497 </p>
 498 <a name="I-want-CBR_002c-but-no-matter-what-I-do-frame-sizes-differ_002e"></a>
 499 <h2 class="section"><a href="faq.html#toc-I-want-CBR_002c-but-no-matter-what-I-do-frame-sizes-differ_002e">3.17 I want CBR, but no matter what I do frame sizes differ.</a></h2>
 500
 501 <p>You do not understand what CBR is, please read the MPEG spec.
 502 Read about video buffer verifier and constant bitrate.
 503 The one sentence summary is that there is a buffer and the input rate is
 504 constant, the output can vary as needed.
 505 </p>
 506 <a name="How-do-I-check-if-a-stream-is-CBR_003f"></a>
 507 <h2 class="section"><a href="faq.html#toc-How-do-I-check-if-a-stream-is-CBR_003f">3.18 How do I check if a stream is CBR?</a></h2>
 508
 509 <p>To quote the MPEG-2 spec:
 510 &quot;There is no way to tell that a bitstream is constant bitrate without
 511 examining all of the vbv_delay values and making complicated computations.&quot;
 512 </p>
 513
 514 <a name="Development"></a>
 515 <h1 class="chapter"><a href="faq.html#toc-Development">4. Development</a></h1>
 516
 517 <a name="Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f"></a>
 518 <h2 class="section"><a href="faq.html#toc-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></h2>
 519
 520 <p>Yes. Read the Developers Guide of the FFmpeg documentation. Alternatively,
 521 examine the source code for one of the many open source projects that
 522 already incorporate FFmpeg at (<a href="projects.html">projects.html</a>).
 523 </p>
 524 <a name="Can-you-support-my-C-compiler-XXX_003f"></a>
 525 <h2 class="section"><a href="faq.html#toc-Can-you-support-my-C-compiler-XXX_003f">4.2 Can you support my C compiler XXX?</a></h2>
 526
 527 <p>It depends. If your compiler is C99-compliant, then patches to support
 528 it are likely to be welcome if they do not pollute the source code
 529 with <code>#ifdef</code>s related to the compiler.
 530 </p>
 531 <a name="Is-Microsoft-Visual-C_002b_002b-supported_003f"></a>
 532 <h2 class="section"><a href="faq.html#toc-Is-Microsoft-Visual-C_002b_002b-supported_003f">4.3 Is Microsoft Visual C++ supported?</a></h2>
 533
 534 <p>No. Microsoft Visual C++ is not compliant to the C99 standard and does
 535 not - among other things - support the inline assembly used in FFmpeg.
 536 If you wish to use MSVC++ for your
 537 project then you can link the MSVC++ code with libav* as long as
 538 you compile the latter with a working C compiler. For more information, see
 539 the <em>Microsoft Visual C++ compatibility</em> section in the FFmpeg
 540 documentation.
 541 </p>
 542 <p>There have been efforts to make FFmpeg compatible with MSVC++ in the
 543 past. However, they have all been rejected as too intrusive, especially
 544 since MinGW does the job adequately. None of the core developers
 545 work with MSVC++ and thus this item is low priority. Should you find
 546 the silver bullet that solves this problem, feel free to shoot it at us.
 547 </p>
 548 <p>We strongly recommend you to move over from MSVC++ to MinGW tools.
 549 </p>
 550 <a name="Can-I-use-FFmpeg-or-libavcodec-under-Windows_003f"></a>
 551 <h2 class="section"><a href="faq.html#toc-Can-I-use-FFmpeg-or-libavcodec-under-Windows_003f">4.4 Can I use FFmpeg or libavcodec under Windows?</a></h2>
 552
 553 <p>Yes, but the Cygwin or MinGW tools <em>must</em> be used to compile FFmpeg.
 554 Read the <em>Windows</em> section in the FFmpeg documentation to find more
 555 information.
 556 </p>
 557 <p>To get help and instructions for building FFmpeg under Windows, check out
 558 the FFmpeg Windows Help Forum at
 559 <a href="http://ffmpeg.arrozcru.org/">http://ffmpeg.arrozcru.org/</a>.
 560 </p>
 561 <a name="Can-you-add-automake_002c-libtool-or-autoconf-support_003f"></a>
 562 <h2 class="section"><a href="faq.html#toc-Can-you-add-automake_002c-libtool-or-autoconf-support_003f">4.5 Can you add automake, libtool or autoconf support?</a></h2>
 563
 564 <p>No. These tools are too bloated and they complicate the build.
 565 </p>
 566 <a name="Why-not-rewrite-ffmpeg-in-object_002doriented-C_002b_002b_003f"></a>
 567 <h2 class="section"><a href="faq.html#toc-Why-not-rewrite-ffmpeg-in-object_002doriented-C_002b_002b_003f">4.6 Why not rewrite ffmpeg in object-oriented C++?</a></h2>
 568
 569 <p>FFmpeg is already organized in a highly modular manner and does not need to
 570 be rewritten in a formal object language. Further, many of the developers
 571 favor straight C; it works for them. For more arguments on this matter,
 572 read <a href="http://www.tux.org/lkml/#s15">&quot;Programming Religion&quot;</a>.
 573 </p>
 574 <a name="Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f"></a>
 575 <h2 class="section"><a href="faq.html#toc-Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f">4.7 Why are the ffmpeg programs devoid of debugging symbols?</a></h2>
 576
 577 <p>The build process creates ffmpeg_g, ffplay_g, etc. which contain full debug
 578 information. Those binaries are stripped to create ffmpeg, ffplay, etc. If
 579 you need the debug information, use the *_g versions.
 580 </p>
 581 <a name="I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f"></a>
 582 <h2 class="section"><a href="faq.html#toc-I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f">4.8 I do not like the LGPL, can I contribute code under the GPL instead?</a></h2>
 583
 584 <p>Yes, as long as the code is optional and can easily and cleanly be placed
 585 under #if CONFIG_GPL without breaking anything. So for example a new codec
 586 or filter would be OK under GPL while a bug fix to LGPL code would not.
 587 </p>
 588 <a name="I-want-to-compile-xyz_002ec-alone-but-my-compiler-produced-many-errors_002e"></a>
 589 <h2 class="section"><a href="faq.html#toc-I-want-to-compile-xyz_002ec-alone-but-my-compiler-produced-many-errors_002e">4.9 I want to compile xyz.c alone but my compiler produced many errors.</a></h2>
 590
 591 <p>Common code is in its own files in libav* and is used by the individual
 592 codecs. They will not work without the common parts, you have to compile
 593 the whole libav*. If you wish, disable some parts with configure switches.
 594 You can also try to hack it and remove more, but if you had problems fixing
 595 the compilation failure then you are probably not qualified for this.
 596 </p>
 597 <a name="I_0027m-using-libavcodec-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e"></a>
 598 <h2 class="section"><a href="faq.html#toc-I_0027m-using-libavcodec-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e">4.10 I&rsquo;m using libavcodec from within my C++ application but the linker complains about missing symbols which seem to be available.</a></h2>
 599
 600 <p>FFmpeg is a pure C project, so to use the libraries within your C++ application
 601 you need to explicitly state that you are using a C library. You can do this by
 602 encompassing your FFmpeg includes using <code>extern &quot;C&quot;</code>.
 603 </p>
 604 <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>
 605 </p>
 606 <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>
 607 <h2 class="section"><a href="faq.html#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">4.11 I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat?</a></h2>
 608
 609 <p>You have to implement a URLProtocol, see &lsquo;<tt>libavformat/file.c</tt>&rsquo; in
 610 FFmpeg and &lsquo;<tt>libmpdemux/demux_lavf.c</tt>&rsquo; in MPlayer sources.
 611 </p>
 612 <a name="I-get-_0022No-compatible-shell-script-interpreter-found_002e_0022-in-MSys_002e"></a>
 613 <h2 class="section"><a href="faq.html#toc-I-get-_0022No-compatible-shell-script-interpreter-found_002e_0022-in-MSys_002e">4.12 I get &quot;No compatible shell script interpreter found.&quot; in MSys.</a></h2>
 614
 615 <p>The standard MSys bash (2.04) is broken. You need to install 2.05 or later.
 616 </p>
 617 <a name="I-get-_0022_002e_002fconfigure_003a-line-_003cxxx_003e_003a-pr_003a-command-not-found_0022-in-MSys_002e"></a>
 618 <h2 class="section"><a href="faq.html#toc-I-get-_0022_002e_002fconfigure_003a-line-_003cxxx_003e_003a-pr_003a-command-not-found_0022-in-MSys_002e">4.13 I get &quot;./configure: line &lt;xxx&gt;: pr: command not found&quot; in MSys.</a></h2>
 619
 620 <p>The standard MSys install doesn&rsquo;t come with pr. You need to get it from the coreutils package.
 621 </p>
 622 <a name="Where-can-I-find-libav_002a-headers-for-Pascal_002fDelphi_003f"></a>
 623 <h2 class="section"><a href="faq.html#toc-Where-can-I-find-libav_002a-headers-for-Pascal_002fDelphi_003f">4.14 Where can I find libav* headers for Pascal/Delphi?</a></h2>
 624
 625 <p>see <a href="http://www.iversenit.dk/dev/ffmpeg-headers/">http://www.iversenit.dk/dev/ffmpeg-headers/</a>
 626 </p>
 627 <a name="Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f"></a>
 628 <h2 class="section"><a href="faq.html#toc-Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f">4.15 Where is the documentation about ffv1, msmpeg4, asv1, 4xm?</a></h2>
 629
 630 <p>see <a href="http://www.ffmpeg.org/~michael/">http://www.ffmpeg.org/~michael/</a>
 631 </p>
 632 <a name="How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f"></a>
 633 <h2 class="section"><a href="faq.html#toc-How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f">4.16 How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?</a></h2>
 634
 635 <p>Even if peculiar since it is network oriented, RTP is a container like any
 636 other. You have to <em>demux</em> RTP before feeding the payload to libavcodec.
 637 In this specific case please look at RFC 4629 to see how it should be done.
 638 </p>
 639 <a name="AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-framerate_002e"></a>
 640 <h2 class="section"><a href="faq.html#toc-AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-framerate_002e">4.17 AVStream.r_frame_rate is wrong, it is much larger than the framerate.</a></h2>
 641
 642 <p>r_frame_rate is NOT the average framerate, it is the smallest framerate
 643 that can accurately represent all timestamps. So no, it is not
 644 wrong if it is larger than the average!
 645 For example, if you have mixed 25 and 30 fps content, then r_frame_rate
 646 will be 150.
 647 </p>
 648 <hr size="1">
 649 <p>
 650  <font size="-1">
 651   This document was generated by <em>Kyle Schwarz</em> on <em>September 2, 2011</em> using <a href="http://www.nongnu.org/texi2html/"><em>texi2html 1.82</em></a>.
 652  </font>
 653  <br>
 654
 655 </p>
 656 </body>
 657 </html>