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diff --git a/doc/faq.texi b/doc/faq.texi index 8044200..fb180fb 100644 --- a/doc/faq.texi +++ b/doc/faq.texi @@ -1,8 +1,8 @@ \input texinfo @c -*- texinfo -*- -@settitle Libav FAQ +@settitle FFmpeg FAQ @titlepage -@center @titlefont{Libav FAQ} +@center @titlefont{FFmpeg FAQ} @end titlepage @top @@ -11,23 +11,23 @@ @chapter General Questions -@section Why doesn't Libav support feature [xyz]? +@section Why doesn't FFmpeg support feature [xyz]? -Because no one has taken on that task yet. Libav development is +Because no one has taken on that task yet. FFmpeg development is driven by the tasks that are important to the individual developers. If there is a feature that is important to you, the best way to get it implemented is to undertake the task yourself or sponsor a developer. -@section Libav does not support codec XXX. Can you include a Windows DLL loader to support it? +@section FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it? No. Windows DLLs are not portable, bloated and often slow. -Moreover Libav strives to support all codecs natively. +Moreover FFmpeg strives to support all codecs natively. A DLL loader is not conducive to that goal. -@section I cannot read this file although this format seems to be supported by avconv. +@section I cannot read this file although this format seems to be supported by ffmpeg. -Even if avconv can read the container format, it may not support all its -codecs. Please consult the supported codec list in the avconv +Even if ffmpeg can read the container format, it may not support all its +codecs. Please consult the supported codec list in the ffmpeg documentation. @section Which codecs are supported by Windows? @@ -81,6 +81,12 @@ problem and an NP-hard problem... @chapter Usage +@section ffmpeg does not work; what is wrong? + +Try a @code{make distclean} in the ffmpeg source directory before the build. +If this does not help see +(@url{http://ffmpeg.org/bugreports.html}). + @section How do I encode single pictures into movies? First, rename your pictures to follow a numerical sequence. @@ -88,7 +94,7 @@ For example, img1.jpg, img2.jpg, img3.jpg,... Then you may run: @example - avconv -f image2 -i img%d.jpg /tmp/a.mpg + ffmpeg -f image2 -i img%d.jpg /tmp/a.mpg @end example Notice that @samp{%d} is replaced by the image number. @@ -111,17 +117,17 @@ If you want to sequence them by oldest modified first, substitute Then run: @example - avconv -f image2 -i /tmp/img%03d.jpg /tmp/a.mpg + ffmpeg -f image2 -i /tmp/img%03d.jpg /tmp/a.mpg @end example -The same logic is used for any image format that avconv reads. +The same logic is used for any image format that ffmpeg reads. @section How do I encode movie to single pictures? Use: @example - avconv -i movie.mpg movie%d.jpg + ffmpeg -i movie.mpg movie%d.jpg @end example The @file{movie.mpg} used as input will be converted to @@ -137,7 +143,7 @@ to force the encoding. Applying that to the previous example: @example - avconv -i movie.mpg -f image2 -c:v mjpeg menu%d.jpg + ffmpeg -i movie.mpg -f image2 -c:v mjpeg menu%d.jpg @end example Beware that there is no "jpeg" codec. Use "mjpeg" instead. @@ -156,12 +162,12 @@ Use @file{-} as file name. Try '-f image2 test%d.jpg'. -@section Why can I not change the framerate? +@section Why can I not change the frame rate? -Some codecs, like MPEG-1/2, only allow a small number of fixed framerates. +Some codecs, like MPEG-1/2, only allow a small number of fixed frame rates. Choose a different codec with the -c:v command line option. -@section How do I encode Xvid or DivX video with avconv? +@section How do I encode Xvid or DivX video with ffmpeg? Both Xvid and DivX (version 4+) are implementations of the ISO MPEG-4 standard (note that there are many other coding formats that use this @@ -182,14 +188,14 @@ things to try: '-bf 2', '-flags qprd', '-flags mv0', '-flags skiprd'. but beware the '-g 100' might cause problems with some decoders. Things to try: '-bf 2', '-flags qprd', '-flags mv0', '-flags skiprd. -@section Interlaced video looks very bad when encoded with avconv, what is wrong? +@section Interlaced video looks very bad when encoded with ffmpeg, what is wrong? You should use '-flags +ilme+ildct' and maybe '-flags +alt' for interlaced material, and try '-top 0/1' if the result looks really messed-up. @section How can I read DirectShow files? -If you have built Libav with @code{./configure --enable-avisynth} +If you have built FFmpeg with @code{./configure --enable-avisynth} (only possible on MinGW/Cygwin platforms), then you may use any file that DirectShow can read as input. @@ -197,9 +203,9 @@ Just create an "input.avs" text file with this single line ... @example DirectShowSource("C:\path to your file\yourfile.asf") @end example -... and then feed that text file to avconv: +... and then feed that text file to ffmpeg: @example - avconv -i input.avs + ffmpeg -i input.avs @end example For ANY other help on Avisynth, please visit the @@ -216,10 +222,10 @@ equally humble @code{copy} under Windows), and finally transcoding back to your format of choice. @example -avconv -i input1.avi -same_quant intermediate1.mpg -avconv -i input2.avi -same_quant intermediate2.mpg +ffmpeg -i input1.avi -same_quant intermediate1.mpg +ffmpeg -i input2.avi -same_quant intermediate2.mpg cat intermediate1.mpg intermediate2.mpg > intermediate_all.mpg -avconv -i intermediate_all.mpg -same_quant output.avi +ffmpeg -i intermediate_all.mpg -same_quant output.avi @end example Notice that you should either use @code{-same_quant} or set a reasonably high @@ -232,10 +238,10 @@ of named pipes, should your platform support it: @example mkfifo intermediate1.mpg mkfifo intermediate2.mpg -avconv -i input1.avi -same_quant -y intermediate1.mpg < /dev/null & -avconv -i input2.avi -same_quant -y intermediate2.mpg < /dev/null & +ffmpeg -i input1.avi -same_quant -y intermediate1.mpg < /dev/null & +ffmpeg -i input2.avi -same_quant -y intermediate2.mpg < /dev/null & cat intermediate1.mpg intermediate2.mpg |\ -avconv -f mpeg -i - -same_quant -c:v mpeg4 -acodec libmp3lame output.avi +ffmpeg -f mpeg -i - -same_quant -c:v mpeg4 -acodec libmp3lame output.avi @end example Similarly, the yuv4mpegpipe format, and the raw video, raw audio codecs also @@ -254,13 +260,13 @@ mkfifo temp2.a mkfifo temp2.v mkfifo all.a mkfifo all.v -avconv -i input1.flv -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 - > temp1.a < /dev/null & -avconv -i input2.flv -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 - > temp2.a < /dev/null & -avconv -i input1.flv -an -f yuv4mpegpipe - > temp1.v < /dev/null & -@{ avconv -i input2.flv -an -f yuv4mpegpipe - < /dev/null | tail -n +2 > temp2.v ; @} & +ffmpeg -i input1.flv -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 - > temp1.a < /dev/null & +ffmpeg -i input2.flv -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 - > temp2.a < /dev/null & +ffmpeg -i input1.flv -an -f yuv4mpegpipe - > temp1.v < /dev/null & +@{ ffmpeg -i input2.flv -an -f yuv4mpegpipe - < /dev/null | tail -n +2 > temp2.v ; @} & cat temp1.a temp2.a > all.a & cat temp1.v temp2.v > all.v & -avconv -f u16le -acodec pcm_s16le -ac 2 -ar 44100 -i all.a \ +ffmpeg -f u16le -acodec pcm_s16le -ac 2 -ar 44100 -i all.a \ -f yuv4mpegpipe -i all.v \ -same_quant -y output.flv rm temp[12].[av] all.[av] @@ -268,7 +274,7 @@ rm temp[12].[av] all.[av] @section -profile option fails when encoding H.264 video with AAC audio -@command{avconv} prints an error like +@command{ffmpeg} prints an error like @example Undefined constant or missing '(' in 'baseline' @@ -283,16 +289,16 @@ video and audio. Specifically the AAC encoder also defines some profiles, none of which are named @var{baseline}. The solution is to apply the @option{-profile} option to the video stream only -by using @url{http://libav.org/avconv.html#Stream-specifiers-1, Stream specifiers}. +by using @url{http://ffmpeg.org/ffmpeg.html#Stream-specifiers-1, Stream specifiers}. Appending @code{:v} to it will do exactly that. @chapter Development -@section Are there examples illustrating how to use the Libav libraries, particularly libavcodec and libavformat? +@section Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat? -Yes. Read the Developers Guide of the Libav documentation. Alternatively, +Yes. Read the Developers Guide of the FFmpeg documentation. Alternatively, examine the source code for one of the many open source projects that -already incorporate Libav at (@url{projects.html}). +already incorporate FFmpeg at (@url{projects.html}). @section Can you support my C compiler XXX? @@ -303,14 +309,14 @@ with @code{#ifdef}s related to the compiler. @section Is Microsoft Visual C++ supported? No. Microsoft Visual C++ is not compliant to the C99 standard and does -not - among other things - support the inline assembly used in Libav. +not - among other things - support the inline assembly used in FFmpeg. If you wish to use MSVC++ for your project then you can link the MSVC++ code with libav* as long as you compile the latter with a working C compiler. For more information, see -the @emph{Microsoft Visual C++ compatibility} section in the Libav +the @emph{Microsoft Visual C++ compatibility} section in the FFmpeg documentation. -There have been efforts to make Libav compatible with MSVC++ in the +There have been efforts to make FFmpeg compatible with MSVC++ in the past. However, they have all been rejected as too intrusive, especially since MinGW does the job adequately. None of the core developers work with MSVC++ and thus this item is low priority. Should you find @@ -318,45 +324,77 @@ the silver bullet that solves this problem, feel free to shoot it at us. We strongly recommend you to move over from MSVC++ to MinGW tools. -@section Can I use Libav under Windows? +@section Can I use FFmpeg or libavcodec under Windows? -Yes, but the Cygwin or MinGW tools @emph{must} be used to compile Libav. -Read the @emph{Windows} section in the Libav documentation to find more +Yes, but the Cygwin or MinGW tools @emph{must} be used to compile FFmpeg. +Read the @emph{Windows} section in the FFmpeg documentation to find more information. +To get help and instructions for building FFmpeg under Windows, check out +the FFmpeg Windows Help Forum at +@url{http://ffmpeg.arrozcru.org/}. + @section Can you add automake, libtool or autoconf support? No. These tools are too bloated and they complicate the build. -@section Why not rewrite Libav in object-oriented C++? +@section Why not rewrite FFmpeg in object-oriented C++? -Libav is already organized in a highly modular manner and does not need to +FFmpeg is already organized in a highly modular manner and does not need to be rewritten in a formal object language. Further, many of the developers favor straight C; it works for them. For more arguments on this matter, read @uref{http://www.tux.org/lkml/#s15, "Programming Religion"}. +@section Why are the ffmpeg programs devoid of debugging symbols? + +The build process creates ffmpeg_g, ffplay_g, etc. which contain full debug +information. Those binaries are stripped to create ffmpeg, ffplay, etc. If +you need the debug information, use the *_g versions. + @section I do not like the LGPL, can I contribute code under the GPL instead? Yes, as long as the code is optional and can easily and cleanly be placed -under #if CONFIG_GPL without breaking anything. So for example a new codec +under #if CONFIG_GPL without breaking anything. So, for example, a new codec or filter would be OK under GPL while a bug fix to LGPL code would not. -@section I'm using Libav from within my C++ application but the linker complains about missing symbols which seem to be available. +@section I'm using FFmpeg from within my C++ application but the linker complains about missing symbols which seem to be available. -Libav is a pure C project, so to use the libraries within your C++ application +FFmpeg is a pure C project, so to use the libraries within your C++ application you need to explicitly state that you are using a C library. You can do this by -encompassing your Libav includes using @code{extern "C"}. +encompassing your FFmpeg includes using @code{extern "C"}. See @url{http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html#faq-32.3} @section I'm using libavutil from within my C++ application but the compiler complains about 'UINT64_C' was not declared in this scope -Libav is a pure C project using C99 math features, in order to enable C++ +FFmpeg is a pure C project using C99 math features, in order to enable C++ to use them you have to append -D__STDC_CONSTANT_MACROS to your CXXFLAGS @section I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat? You have to implement a URLProtocol, see @file{libavformat/file.c} in -Libav and @file{libmpdemux/demux_lavf.c} in MPlayer sources. +FFmpeg and @file{libmpdemux/demux_lavf.c} in MPlayer sources. + +@section Where can I find libav* headers for Pascal/Delphi? + +see @url{http://www.iversenit.dk/dev/ffmpeg-headers/} + +@section Where is the documentation about ffv1, msmpeg4, asv1, 4xm? + +see @url{http://www.ffmpeg.org/~michael/} + +@section How do I feed H.263-RTP (and other codecs in RTP) to libavcodec? + +Even if peculiar since it is network oriented, RTP is a container like any +other. You have to @emph{demux} RTP before feeding the payload to libavcodec. +In this specific case please look at RFC 4629 to see how it should be done. + +@section AVStream.r_frame_rate is wrong, it is much larger than the frame rate. + +r_frame_rate is NOT the average frame rate, it is the smallest frame rate +that can accurately represent all timestamps. So no, it is not +wrong if it is larger than the average! +For example, if you have mixed 25 and 30 fps content, then r_frame_rate +will be 150. @bye |
