X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=doc%2Ffaq.texi;h=cf86616f9ed98f9b662e21b53726a77c37edbaa8;hb=7a05b0a675f7089076e1972368c0ca4cbdc2a18a;hp=a7222b8998698f72ba52c8333fdcd670d5f9404b;hpb=a28d9122d2c09296ba323ad62a7ff9956e394bc7;p=ffmpeg diff --git a/doc/faq.texi b/doc/faq.texi index a7222b89986..cf86616f9ed 100644 --- a/doc/faq.texi +++ b/doc/faq.texi @@ -38,7 +38,7 @@ No. Windows DLLs are not portable, bloated and often slow. Moreover FFmpeg strives to support all codecs natively. A DLL loader is not conducive to that goal. -@section My bugreport/mail to ffmpeg-devel/user has not received any replies. +@section My bug report/mail to ffmpeg-devel/user has not received any replies. Likely reasons @itemize @@ -58,7 +58,9 @@ that it is related to FFmpeg. @section Is there a forum for FFmpeg? I do not like mailing lists. -Yes, (@url{http://dir.gmane.org/gmane.comp.video.ffmpeg.user}). +You may view our mailing lists with a more forum-alike look here: +@url{http://dir.gmane.org/gmane.comp.video.ffmpeg.user}, +but, if you post, please remember that our mailing list rules still apply there. @section I cannot read this file although this format seems to be supported by ffmpeg. @@ -69,7 +71,7 @@ documentation. @section Which codecs are supported by Windows? Windows does not support standard formats like MPEG very well, unless you -install some additional codecs +install some additional codecs. The following list of video codecs should work on most Windows systems: @table @option @@ -82,7 +84,7 @@ The following list of video codecs should work on most Windows systems: @item wmv2 .asf only @item mpeg4 -only if you have some MPEG-4 codec installed like ffdshow or Xvid +Only if you have some MPEG-4 codec like ffdshow or Xvid installed. @item mpeg1 .mpg only @end table @@ -96,8 +98,9 @@ The following list of audio codecs should work on most Windows systems: @item adpcm_ima_wav @item adpcm_ms @item pcm +always @item mp3 -if some MP3 codec like LAME is installed +If some MP3 codec like LAME is installed. @end table @@ -108,15 +111,20 @@ if some MP3 codec like LAME is installed This is a bug in gcc. Do not report it to us. Instead, please report it to the gcc developers. Note that we will not add workarounds for gcc bugs. +Also note that (some of) the gcc developers believe this is not a bug or +not a bug they should fix: +@url{http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203}. +Then again, some of them do not know the difference between an undecidable +problem and an NP-hard problem... @chapter Usage -@section ffmpeg does not work; What is wrong? +@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 to movies? +@section How do I encode single pictures into movies? First, rename your pictures to follow a numerical sequence. For example, img1.jpg, img2.jpg, img3.jpg,... @@ -158,10 +166,6 @@ Applying that to the previous example: Beware that there is no "jpeg" codec. Use "mjpeg" instead. -@section I get "Unsupported codec (id=86043) for input stream #0.1". What is the problem? - -This is the Qcelp codec, FFmpeg has no support for that codec currently. Try mencoder/mplayer it might work. - @section Why do I see a slight quality degradation with multithreaded MPEG* encoding? For multithreaded MPEG* encoding, the encoded slices must be independent, @@ -170,27 +174,19 @@ quite logical that there is a small reduction of quality. This is not a bug. @section How can I read from the standard input or write to the standard output? -Use @file{-} as filename. - -@section Why does FFmpeg not decode audio in VOB files? - -The audio is AC-3 (a.k.a. A/52). AC-3 decoding is an optional component in FFmpeg -as the component that handles AC-3 decoding is currently released under the GPL. -Enable AC-3 decoding with @code{./configure --enable-gpl}. Take care: By -enabling AC-3, you automatically change the license of libavcodec from -LGPL to GPL. +Use @file{-} as file name. @section Why does the chrominance data seem to be sampled at a different time from the luminance data on bt8x8 captures on Linux? This is a well-known bug in the bt8x8 driver. For 2.4.26 there is a patch at -(@url{http://svn.mplayerhq.hu/michael/trunk/patches/bttv-420-2.4.26.patch?view=co}). This may also +(@url{http://svn.ffmpeg.org/michael/trunk/patches/bttv-420-2.4.26.patch?view=co}). This may also apply cleanly to other 2.4-series kernels. @section How do I avoid the ugly aliasing artifacts in bt8x8 captures on Linux? Pass 'combfilter=1 lumafilter=1' to the bttv driver. Note though that 'combfilter=1' -will cause somewhat too strong filtering. A fix is to apply (@url{http://svn.mplayerhq.hu/michael/trunk/patches/bttv-comb-2.4.26.patch?view=co}) -or (@url{http://svn.mplayerhq.hu/michael/trunk/patches/bttv-comb-2.6.6.patch?view=co}) +will cause somewhat too strong filtering. A fix is to apply (@url{http://svn.ffmpeg.org/michael/trunk/patches/bttv-comb-2.4.26.patch?view=co}) +or (@url{http://svn.ffmpeg.org/michael/trunk/patches/bttv-comb-2.6.6.patch?view=co}) and pass 'combfilter=2'. @section -f jpeg doesn't work. @@ -206,7 +202,7 @@ Choose a different codec with the -vcodec command line option. 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 -same standard). Thus, use '-vcodec mpeg4' to encode these formats. The +same standard). Thus, use '-vcodec mpeg4' to encode in these formats. The default fourcc stored in an MPEG-4-coded file will be 'FMP4'. If you want a different fourcc, use the '-vtag' option. E.g., '-vtag xvid' will force the fourcc 'xvid' to be stored as the video fourcc rather than the @@ -222,7 +218,7 @@ default. @item non-working stuff B-frames @item example command line -ffmpeg -i input -acodec libfaac -ab 128kb -vcodec mpeg4 -b 1200kb -mbd 2 -flags +4mv+trell -aic 2 -cmp 2 -subcmp 2 -s 320x180 -title X output.mp4 +ffmpeg -i input -acodec libfaac -ab 128kb -vcodec mpeg4 -b 1200kb -mbd 2 -flags +4mv -trellis 2 -aic 2 -cmp 2 -subcmp 2 -s 320x180 -title X output.mp4 @end table @section How do I encode videos which play on the PSP? @@ -235,29 +231,33 @@ ffmpeg -i input -acodec libfaac -ab 128kb -vcodec mpeg4 -b 1200kb -mbd 2 -flags @item non-working stuff B-frames @item example command line -ffmpeg -i input -acodec libfaac -ab 128kb -vcodec mpeg4 -b 1200kb -ar 24000 -mbd 2 -flags +4mv+trell -aic 2 -cmp 2 -subcmp 2 -s 368x192 -r 30000/1001 -title X -f psp output.mp4 +ffmpeg -i input -acodec libfaac -ab 128kb -vcodec mpeg4 -b 1200kb -ar 24000 -mbd 2 -flags +4mv -trellis 2 -aic 2 -cmp 2 -subcmp 2 -s 368x192 -r 30000/1001 -title X -f psp output.mp4 @item needed stuff for H.264 --acodec libfaac -vcodec h264 width*height<=76800 width%16=0? height%16=0? -ar 48000 -coder 1 -r 30000/1001 or 15000/1001 -f psp +-acodec libfaac -vcodec libx264 width*height<=76800 width%16=0? height%16=0? -ar 48000 -coder 1 -r 30000/1001 or 15000/1001 -f psp @item working stuff for H.264 title, loop filter @item non-working stuff for H.264 CAVLC @item example command line -ffmpeg -i input -acodec libfaac -ab 128kb -vcodec h264 -b 1200kb -ar 48000 -mbd 2 -coder 1 -cmp 2 -subcmp 2 -s 368x192 -r 30000/1001 -title X -f psp -flags loop -trellis 2 -partitions parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 output.mp4 +ffmpeg -i input -acodec libfaac -ab 128kb -vcodec libx264 -b 1200kb -ar 48000 -mbd 2 -coder 1 -cmp 2 -subcmp 2 -s 368x192 -r 30000/1001 -title X -f psp -flags loop -trellis 2 -partitions parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 output.mp4 +@item higher resolution for newer PSP firmwares, width<=480, height<=272 +-vcodec libx264 -level 21 -coder 1 -f psp +@item example command line +ffmpeg -i input -acodec libfaac -ab 128kb -ac 2 -ar 48000 -vcodec libx264 -level 21 -b 640kb -coder 1 -f psp -flags +loop -trellis 2 -partitions +parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 -g 250 -s 480x272 output.mp4 @end table @section Which are good parameters for encoding high quality MPEG-4? -'-mbd rd -flags +4mv+trell+aic -cmp 2 -subcmp 2 -g 300 -pass 1/2', +'-mbd rd -flags +4mv+aic -trellis 2 -cmp 2 -subcmp 2 -g 300 -pass 1/2', things to try: '-bf 2', '-flags qprd', '-flags mv0', '-flags skiprd'. @section Which are good parameters for encoding high quality MPEG-1/MPEG-2? -'-mbd rd -flags +trell -cmp 2 -subcmp 2 -g 100 -pass 1/2' +'-mbd rd -trellis 2 -cmp 2 -subcmp 2 -g 100 -pass 1/2' 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 ffmpeg, whats 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. @@ -316,6 +316,11 @@ ffmpeg -f mpeg -i - -sameq -vcodec mpeg4 -acodec libmp3lame output.avi Similarly, the yuv4mpegpipe format, and the raw video, raw audio codecs also allow concatenation, and the transcoding step is almost lossless. +When using multiple yuv4mpegpipe(s), the first line needs to be discarded +from all but the first stream. This can be accomplished by piping through +@code{tail} as seen below. Note that when piping through @code{tail} you +must use command grouping, @code{@{ ;@}}, to background properly. + For example, let's say we want to join two FLV files into an output.flv file: @@ -329,7 +334,7 @@ mkfifo all.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 - > temp2.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 & ffmpeg -f u16le -acodec pcm_s16le -ac 2 -ar 44100 -i all.a \ @@ -362,7 +367,7 @@ examining all of the vbv_delay values and making complicated computations." 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 ffmpeg at (@url{projects.html}). +already incorporate FFmpeg at (@url{projects.html}). @section Can you support my C compiler XXX? @@ -396,7 +401,7 @@ information. To get help and instructions for building FFmpeg under Windows, check out the FFmpeg Windows Help Forum at -@url{http://arrozcru.no-ip.org/ffmpeg/}. +@url{http://ffmpeg.arrozcru.org/}. @section Can you add automake, libtool or autoconf support? @@ -404,7 +409,7 @@ No. These tools are too bloated and they complicate the build. @section Why not rewrite ffmpeg in object-oriented C++? -ffmpeg 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 "Programming Religion" at (@url{http://www.tux.org/lkml/#s15}). @@ -412,14 +417,14 @@ read "Programming Religion" at (@url{http://www.tux.org/lkml/#s15}). @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 strip'd to create ffmpeg, ffplay, etc. If +information. Those binaries are stripped to create ffmpeg, ffplay, etc. If you need the debug information, used 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 #ifdef CONFIG_GPL without breaking anything. So for example a new codec -or filter would be OK under GPL while a bugfix to LGPL code would not. +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 want to compile xyz.c alone but my compiler produced many errors. @@ -461,7 +466,7 @@ see @url{http://www.iversenit.dk/dev/ffmpeg-headers/} @section Where is the documentation about ffv1, msmpeg4, asv1, 4xm? -see @url{http://svn.mplayerhq.hu/michael/trunk/docs/} +see @url{http://svn.ffmpeg.org/michael/trunk/docs/} @section How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?