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doc: remove some stale entries from the faq

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Some entries should be still amended.
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Luca Barbato 2011-12-10 01:52:05 +01:00
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@ -11,22 +11,6 @@
@chapter General Questions
@section When will the next Libav version be released? / Why are Libav releases so few and far between?
Like most open source projects Libav suffers from a certain lack of
manpower. For this reason the developers have to prioritize the work
they do and putting out releases is not at the top of the list, fixing
bugs and reviewing patches takes precedence. Please don't complain or
request more timely and/or frequent releases unless you are willing to
help out creating them.
@section I have a problem with an old version of Libav; where should I report it?
Nowhere. We do not support old Libav versions in any way, we simply lack
the time, motivation and manpower to do so. If you have a problem with an
old version of Libav, upgrade to the latest git snapshot. If you
still experience the problem, then you can report it according to our
@uref{http://libav.org/bugreports.html, bug reporting guidelines}.
@section Why doesn't Libav support feature [xyz]?
Because no one has taken on that task yet. Libav development is
@ -40,31 +24,6 @@ No. Windows DLLs are not portable, bloated and often slow.
Moreover Libav strives to support all codecs natively.
A DLL loader is not conducive to that goal.
@section My bug report/mail to libav-devel/user has not received any replies.
Likely reasons
@itemize
@item We are busy and haven't had time yet to read your report or
investigate the issue.
@item You did not follow our
@uref{http://libav.org/bugreports.html, bug reporting guidelines}.
@item You didn't use git master.
@item You reported a segmentation fault without gdb output.
@item You describe a problem but not how to reproduce it.
@item It's unclear if you use ffmpeg as command line tool or use
libav* from another application.
@item You speak about a video having problems on playback but
not what you use to play it.
@item We have no faint clue what you are talking about besides
that it is related to Libav.
@end itemize
@section Is there a forum for Libav? I do not like mailing lists.
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.
Even if ffmpeg can read the container format, it may not support all its
@ -218,44 +177,6 @@ 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
default.
@section How do I encode videos which play on the iPod?
@table @option
@item needed stuff
-acodec libfaac -vcodec mpeg4 width<=320 height<=240
@item working stuff
mv4, title
@item non-working stuff
B-frames
@item example command line
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
@end table
@section How do I encode videos which play on the PSP?
@table @option
@item needed stuff
-acodec libfaac -vcodec mpeg4 width*height<=76800 width%16=0 height%16=0 -ar 24000 -r 30000/1001 or 15000/1001 -f psp
@item working stuff
mv4, title
@item non-working stuff
B-frames
@item example command line
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
@item needed stuff for H.264
-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 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
@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 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
@end table
@section Which are good parameters for encoding high quality MPEG-4?
'-mbd rd -flags +mv4+aic -trellis 2 -cmp 2 -subcmp 2 -g 300 -pass 1/2',
@ -351,24 +272,6 @@ ffmpeg -f u16le -acodec pcm_s16le -ac 2 -ar 44100 -i all.a \
rm temp[12].[av] all.[av]
@end example
@section The ffmpeg program does not respect the -maxrate setting, some frames are bigger than maxrate/fps.
Read the MPEG spec about video buffer verifier.
@section I want CBR, but no matter what I do frame sizes differ.
You do not understand what CBR is, please read the MPEG spec.
Read about video buffer verifier and constant bitrate.
The one sentence summary is that there is a buffer and the input rate is
constant, the output can vary as needed.
@section How do I check if a stream is CBR?
To quote the MPEG-2 spec:
"There is no way to tell that a bitstream is constant bitrate without
examining all of the vbv_delay values and making complicated computations."
@chapter Development
@section Are there examples illustrating how to use the Libav libraries, particularly libavcodec and libavformat?
@ -424,14 +327,6 @@ 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
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.
Common code is in its own files in libav* and is used by the individual
codecs. They will not work without the common parts, you have to compile
the whole libav*. If you wish, disable some parts with configure switches.
You can also try to hack it and remove more, but if you had problems fixing
the compilation failure then you are probably not qualified for this.
@section I'm using libavcodec 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
@ -450,34 +345,4 @@ to use them you have to append -D__STDC_CONSTANT_MACROS to your CXXFLAGS
You have to implement a URLProtocol, see @file{libavformat/file.c} in
Libav and @file{libmpdemux/demux_lavf.c} in MPlayer sources.
@section I get "No compatible shell script interpreter found." in MSys.
The standard MSys bash (2.04) is broken. You need to install 2.05 or later.
@section I get "./configure: line <xxx>: pr: command not found" in MSys.
The standard MSys install doesn't come with pr. You need to get it from the coreutils package.
@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 framerate.
r_frame_rate is NOT the average framerate, it is the smallest framerate
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