2002-11-04 18:50:04 +00:00
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\input texinfo @c -*- texinfo -*-
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@documentencoding UTF-8
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2002-11-04 18:50:04 +00:00
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2011-03-17 15:55:58 +00:00
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@settitle FFmpeg FAQ
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2002-11-04 18:50:04 +00:00
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@titlepage
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2011-03-17 15:55:58 +00:00
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@center @titlefont{FFmpeg FAQ}
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2002-11-04 18:50:04 +00:00
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@end titlepage
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2011-01-29 12:24:13 +00:00
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@top
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@contents
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2002-11-04 18:50:04 +00:00
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2008-01-26 12:18:28 +00:00
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@chapter General Questions
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2011-03-17 15:55:58 +00:00
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@section Why doesn't FFmpeg support feature [xyz]?
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2008-01-26 12:18:28 +00:00
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2011-03-17 15:55:58 +00:00
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Because no one has taken on that task yet. FFmpeg development is
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2008-01-26 12:18:28 +00:00
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driven by the tasks that are important to the individual developers.
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If there is a feature that is important to you, the best way to get
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2008-01-26 12:23:24 +00:00
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it implemented is to undertake the task yourself or sponsor a developer.
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2011-03-17 15:55:58 +00:00
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@section FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it?
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2008-01-26 12:18:28 +00:00
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2008-01-26 12:23:24 +00:00
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No. Windows DLLs are not portable, bloated and often slow.
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2011-03-17 15:55:58 +00:00
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Moreover FFmpeg strives to support all codecs natively.
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2008-01-26 12:23:24 +00:00
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A DLL loader is not conducive to that goal.
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2004-10-01 02:35:21 +00:00
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@section I cannot read this file although this format seems to be supported by ffmpeg.
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2002-11-04 18:50:04 +00:00
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2008-01-26 12:23:24 +00:00
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Even if ffmpeg can read the container format, it may not support all its
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codecs. Please consult the supported codec list in the ffmpeg
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documentation.
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2008-01-26 12:18:28 +00:00
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@section Which codecs are supported by Windows?
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Windows does not support standard formats like MPEG very well, unless you
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install some additional codecs.
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The following list of video codecs should work on most Windows systems:
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@table @option
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@item msmpeg4v2
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.avi/.asf
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@item msmpeg4
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.asf only
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@item wmv1
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.asf only
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@item wmv2
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.asf only
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@item mpeg4
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Only if you have some MPEG-4 codec like ffdshow or Xvid installed.
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@item mpeg1video
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.mpg only
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@end table
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Note, ASF files often have .wmv or .wma extensions in Windows. It should also
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be mentioned that Microsoft claims a patent on the ASF format, and may sue
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or threaten users who create ASF files with non-Microsoft software. It is
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strongly advised to avoid ASF where possible.
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The following list of audio codecs should work on most Windows systems:
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@table @option
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@item adpcm_ima_wav
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@item adpcm_ms
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@item pcm_s16le
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always
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@item libmp3lame
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If some MP3 codec like LAME is installed.
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@end table
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2008-05-28 16:12:40 +00:00
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@chapter Compilation
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@section @code{error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'}
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This is a bug in gcc. Do not report it to us. Instead, please report it to
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the gcc developers. Note that we will not add workarounds for gcc bugs.
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2008-07-29 07:55:51 +00:00
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Also note that (some of) the gcc developers believe this is not a bug or
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not a bug they should fix:
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@url{http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203}.
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Then again, some of them do not know the difference between an undecidable
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problem and an NP-hard problem...
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2008-05-28 16:12:40 +00:00
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2012-11-07 22:55:17 +00:00
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@section I have installed this library with my distro's package manager. Why does @command{configure} not see it?
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Distributions usually split libraries in several packages. The main package
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contains the files necessary to run programs using the library. The
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development package contains the files necessary to build programs using the
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library. Sometimes, docs and/or data are in a separate package too.
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To build FFmpeg, you need to install the development package. It is usually
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called @file{libfoo-dev} or @file{libfoo-devel}. You can remove it after the
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build is finished, but be sure to keep the main package.
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2014-12-23 09:34:48 +00:00
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@section How do I make @command{pkg-config} find my libraries?
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Somewhere along with your libraries, there is a @file{.pc} file (or several)
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in a @file{pkgconfig} directory. You need to set environment variables to
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point @command{pkg-config} to these files.
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If you need to @emph{add} directories to @command{pkg-config}'s search list
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(typical use case: library installed separately), add it to
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@code{$PKG_CONFIG_PATH}:
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@example
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export PKG_CONFIG_PATH=/opt/x264/lib/pkgconfig:/opt/opus/lib/pkgconfig
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@end example
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If you need to @emph{replace} @command{pkg-config}'s search list
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(typical use case: cross-compiling), set it in
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@code{$PKG_CONFIG_LIBDIR}:
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@example
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export PKG_CONFIG_LIBDIR=/home/me/cross/usr/lib/pkgconfig:/home/me/cross/usr/local/lib/pkgconfig
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@end example
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If you need to know the library's internal dependencies (typical use: static
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linking), add the @code{--static} option to @command{pkg-config}:
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@example
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./configure --pkg-config-flags=--static
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@end example
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@section How do I use @command{pkg-config} when cross-compiling?
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The best way is to install @command{pkg-config} in your cross-compilation
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environment. It will automatically use the cross-compilation libraries.
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You can also use @command{pkg-config} from the host environment by
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specifying explicitly @code{--pkg-config=pkg-config} to @command{configure}.
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In that case, you must point @command{pkg-config} to the correct directories
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using the @code{PKG_CONFIG_LIBDIR}, as explained in the previous entry.
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As an intermediate solution, you can place in your cross-compilation
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environment a script that calls the host @command{pkg-config} with
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@code{PKG_CONFIG_LIBDIR} set. That script can look like that:
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@example
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#!/bin/sh
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PKG_CONFIG_LIBDIR=/path/to/cross/lib/pkgconfig
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export PKG_CONFIG_LIBDIR
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exec /usr/bin/pkg-config "$@@"
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@end example
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2008-01-26 12:18:28 +00:00
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@chapter Usage
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2008-06-06 07:51:36 +00:00
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@section ffmpeg does not work; what is wrong?
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2008-01-26 12:18:28 +00:00
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2011-07-08 13:33:17 +00:00
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Try a @code{make distclean} in the ffmpeg source directory before the build.
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2011-07-12 22:42:11 +00:00
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If this does not help see
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(@url{https://ffmpeg.org/bugreports.html}).
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2008-06-06 07:51:36 +00:00
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@section How do I encode single pictures into movies?
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2007-06-01 12:03:33 +00:00
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First, rename your pictures to follow a numerical sequence.
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For example, img1.jpg, img2.jpg, img3.jpg,...
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Then you may run:
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@example
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ffmpeg -f image2 -i img%d.jpg /tmp/a.mpg
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@end example
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2007-06-01 12:03:33 +00:00
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Notice that @samp{%d} is replaced by the image number.
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2012-06-25 22:37:01 +00:00
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@file{img%03d.jpg} means the sequence @file{img001.jpg}, @file{img002.jpg}, etc.
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Use the @option{-start_number} option to declare a starting number for
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the sequence. This is useful if your sequence does not start with
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@file{img001.jpg} but is still in a numerical order. The following
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example will start with @file{img100.jpg}:
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@example
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ffmpeg -f image2 -start_number 100 -i img%d.jpg /tmp/a.mpg
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@end example
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2010-01-19 22:05:02 +00:00
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If you have large number of pictures to rename, you can use the
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following command to ease the burden. The command, using the bourne
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shell syntax, symbolically links all files in the current directory
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that match @code{*jpg} to the @file{/tmp} directory in the sequence of
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@file{img001.jpg}, @file{img002.jpg} and so on.
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@example
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x=1; for i in *jpg; do counter=$(printf %03d $x); ln -s "$i" /tmp/img"$counter".jpg; x=$(($x+1)); done
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@end example
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If you want to sequence them by oldest modified first, substitute
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@code{$(ls -r -t *jpg)} in place of @code{*jpg}.
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Then run:
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@example
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ffmpeg -f image2 -i /tmp/img%03d.jpg /tmp/a.mpg
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2010-01-19 22:05:02 +00:00
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@end example
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2007-06-01 12:03:33 +00:00
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The same logic is used for any image format that ffmpeg reads.
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2012-06-25 22:37:01 +00:00
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You can also use @command{cat} to pipe images to ffmpeg:
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@example
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cat *.jpg | ffmpeg -f image2pipe -c:v mjpeg -i - output.mpg
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@end example
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2007-06-21 05:14:00 +00:00
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@section How do I encode movie to single pictures?
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2006-08-24 14:03:08 +00:00
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2006-11-05 13:31:57 +00:00
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Use:
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@example
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ffmpeg -i movie.mpg movie%d.jpg
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@end example
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2006-11-05 13:31:57 +00:00
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The @file{movie.mpg} used as input will be converted to
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@file{movie1.jpg}, @file{movie2.jpg}, etc...
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Instead of relying on file format self-recognition, you may also use
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@table @option
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@item -c:v ppm
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@item -c:v png
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@item -c:v mjpeg
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@end table
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to force the encoding.
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Applying that to the previous example:
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@example
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ffmpeg -i movie.mpg -f image2 -c:v mjpeg menu%d.jpg
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@end example
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Beware that there is no "jpeg" codec. Use "mjpeg" instead.
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2007-06-21 05:14:00 +00:00
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@section Why do I see a slight quality degradation with multithreaded MPEG* encoding?
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2004-08-23 19:48:41 +00:00
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For multithreaded MPEG* encoding, the encoded slices must be independent,
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otherwise thread n would practically have to wait for n-1 to finish, so it's
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quite logical that there is a small reduction of quality. This is not a bug.
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2004-08-23 19:48:41 +00:00
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2007-06-21 05:14:00 +00:00
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@section How can I read from the standard input or write to the standard output?
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2002-11-19 19:16:26 +00:00
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2008-06-06 07:51:36 +00:00
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Use @file{-} as file name.
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2002-11-19 19:16:26 +00:00
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2005-06-09 19:54:58 +00:00
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@section -f jpeg doesn't work.
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2004-07-09 20:11:52 +00:00
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2006-08-24 14:03:08 +00:00
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Try '-f image2 test%d.jpg'.
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2004-07-09 20:11:52 +00:00
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2011-11-29 16:50:25 +00:00
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@section Why can I not change the frame rate?
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2004-09-12 16:46:15 +00:00
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2011-11-29 16:50:25 +00:00
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Some codecs, like MPEG-1/2, only allow a small number of fixed frame rates.
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2011-12-10 00:58:04 +00:00
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Choose a different codec with the -c:v command line option.
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2004-09-12 16:46:15 +00:00
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2008-05-27 12:32:59 +00:00
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@section How do I encode Xvid or DivX video with ffmpeg?
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2004-10-16 16:47:42 +00:00
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2008-05-27 12:32:59 +00:00
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Both Xvid and DivX (version 4+) are implementations of the ISO MPEG-4
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standard (note that there are many other coding formats that use this
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same standard). Thus, use '-c:v mpeg4' to encode in these formats. The
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2005-06-09 17:55:36 +00:00
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default fourcc stored in an MPEG-4-coded file will be 'FMP4'. If you want
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2005-12-17 18:14:38 +00:00
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a different fourcc, use the '-vtag' option. E.g., '-vtag xvid' will
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force the fourcc 'xvid' to be stored as the video fourcc rather than the
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default.
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|
2007-01-15 05:46:42 +00:00
|
|
|
|
@section Which are good parameters for encoding high quality MPEG-4?
|
2007-01-02 01:19:58 +00:00
|
|
|
|
|
2010-10-03 17:15:18 +00:00
|
|
|
|
'-mbd rd -flags +mv4+aic -trellis 2 -cmp 2 -subcmp 2 -g 300 -pass 1/2',
|
2007-01-15 05:46:42 +00:00
|
|
|
|
things to try: '-bf 2', '-flags qprd', '-flags mv0', '-flags skiprd'.
|
2007-01-02 01:19:58 +00:00
|
|
|
|
|
2007-01-15 05:46:42 +00:00
|
|
|
|
@section Which are good parameters for encoding high quality MPEG-1/MPEG-2?
|
2007-01-02 01:19:58 +00:00
|
|
|
|
|
2008-11-29 13:58:41 +00:00
|
|
|
|
'-mbd rd -trellis 2 -cmp 2 -subcmp 2 -g 100 -pass 1/2'
|
2007-01-15 05:46:42 +00:00
|
|
|
|
but beware the '-g 100' might cause problems with some decoders.
|
|
|
|
|
Things to try: '-bf 2', '-flags qprd', '-flags mv0', '-flags skiprd.
|
2007-01-02 01:19:58 +00:00
|
|
|
|
|
2008-07-27 12:36:58 +00:00
|
|
|
|
@section Interlaced video looks very bad when encoded with ffmpeg, what is wrong?
|
2007-01-02 01:19:58 +00:00
|
|
|
|
|
2007-01-15 05:46:42 +00:00
|
|
|
|
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.
|
2007-01-02 01:19:58 +00:00
|
|
|
|
|
2006-09-17 07:34:54 +00:00
|
|
|
|
@section How can I read DirectShow files?
|
2006-09-16 12:40:18 +00:00
|
|
|
|
|
2011-03-17 15:55:58 +00:00
|
|
|
|
If you have built FFmpeg with @code{./configure --enable-avisynth}
|
2006-09-17 07:34:54 +00:00
|
|
|
|
(only possible on MinGW/Cygwin platforms),
|
|
|
|
|
then you may use any file that DirectShow can read as input.
|
2006-09-16 12:40:18 +00:00
|
|
|
|
|
|
|
|
|
Just create an "input.avs" text file with this single line ...
|
|
|
|
|
@example
|
2013-09-24 19:42:21 +00:00
|
|
|
|
DirectShowSource("C:\path to your file\yourfile.asf")
|
2006-09-16 12:40:18 +00:00
|
|
|
|
@end example
|
2011-04-23 14:40:01 +00:00
|
|
|
|
... and then feed that text file to ffmpeg:
|
2006-09-16 12:40:18 +00:00
|
|
|
|
@example
|
2013-09-24 19:42:21 +00:00
|
|
|
|
ffmpeg -i input.avs
|
2006-09-16 12:40:18 +00:00
|
|
|
|
@end example
|
|
|
|
|
|
2013-05-04 19:18:13 +00:00
|
|
|
|
For ANY other help on AviSynth, please visit the
|
|
|
|
|
@uref{http://www.avisynth.org/, AviSynth homepage}.
|
2006-09-16 12:40:18 +00:00
|
|
|
|
|
2007-06-02 21:50:45 +00:00
|
|
|
|
@section How can I join video files?
|
|
|
|
|
|
2012-07-23 12:35:10 +00:00
|
|
|
|
To "join" video files is quite ambiguous. The following list explains the
|
|
|
|
|
different kinds of "joining" and points out how those are addressed in
|
|
|
|
|
FFmpeg. To join video files may mean:
|
|
|
|
|
|
|
|
|
|
@itemize
|
|
|
|
|
|
|
|
|
|
@item
|
|
|
|
|
To put them one after the other: this is called to @emph{concatenate} them
|
|
|
|
|
(in short: concat) and is addressed
|
|
|
|
|
@ref{How can I concatenate video files, in this very faq}.
|
|
|
|
|
|
|
|
|
|
@item
|
|
|
|
|
To put them together in the same file, to let the user choose between the
|
|
|
|
|
different versions (example: different audio languages): this is called to
|
|
|
|
|
@emph{multiplex} them together (in short: mux), and is done by simply
|
|
|
|
|
invoking ffmpeg with several @option{-i} options.
|
|
|
|
|
|
|
|
|
|
@item
|
|
|
|
|
For audio, to put all channels together in a single stream (example: two
|
|
|
|
|
mono streams into one stereo stream): this is sometimes called to
|
|
|
|
|
@emph{merge} them, and can be done using the
|
2016-10-22 18:12:30 +00:00
|
|
|
|
@url{ffmpeg-filters.html#amerge, @code{amerge}} filter.
|
2012-07-23 12:35:10 +00:00
|
|
|
|
|
|
|
|
|
@item
|
|
|
|
|
For audio, to play one on top of the other: this is called to @emph{mix}
|
|
|
|
|
them, and can be done by first merging them into a single stream and then
|
2016-10-22 18:12:30 +00:00
|
|
|
|
using the @url{ffmpeg-filters.html#pan, @code{pan}} filter to mix
|
2012-07-23 12:35:10 +00:00
|
|
|
|
the channels at will.
|
|
|
|
|
|
|
|
|
|
@item
|
|
|
|
|
For video, to display both together, side by side or one on top of a part of
|
|
|
|
|
the other; it can be done using the
|
2016-10-22 18:12:30 +00:00
|
|
|
|
@url{ffmpeg-filters.html#overlay, @code{overlay}} video filter.
|
2012-07-23 12:35:10 +00:00
|
|
|
|
|
|
|
|
|
@end itemize
|
|
|
|
|
|
|
|
|
|
@anchor{How can I concatenate video files}
|
|
|
|
|
@section How can I concatenate video files?
|
|
|
|
|
|
2012-07-23 13:02:57 +00:00
|
|
|
|
There are several solutions, depending on the exact circumstances.
|
|
|
|
|
|
2012-12-19 21:33:41 +00:00
|
|
|
|
@subsection Concatenating using the concat @emph{filter}
|
2012-07-23 13:02:57 +00:00
|
|
|
|
|
2016-10-22 18:12:30 +00:00
|
|
|
|
FFmpeg has a @url{ffmpeg-filters.html#concat,
|
2012-12-19 21:33:41 +00:00
|
|
|
|
@code{concat}} filter designed specifically for that, with examples in the
|
|
|
|
|
documentation. This operation is recommended if you need to re-encode.
|
2012-07-23 13:02:57 +00:00
|
|
|
|
|
2012-12-19 21:33:41 +00:00
|
|
|
|
@subsection Concatenating using the concat @emph{demuxer}
|
|
|
|
|
|
2016-10-22 18:12:30 +00:00
|
|
|
|
FFmpeg has a @url{ffmpeg-formats.html#concat,
|
2012-12-19 21:33:41 +00:00
|
|
|
|
@code{concat}} demuxer which you can use when you want to avoid a re-encode and
|
|
|
|
|
your format doesn't support file level concatenation.
|
|
|
|
|
|
|
|
|
|
@subsection Concatenating using the concat @emph{protocol} (file level)
|
2012-07-23 13:02:57 +00:00
|
|
|
|
|
2016-10-22 18:12:30 +00:00
|
|
|
|
FFmpeg has a @url{ffmpeg-protocols.html#concat,
|
2013-01-24 13:03:46 +00:00
|
|
|
|
@code{concat}} protocol designed specifically for that, with examples in the
|
|
|
|
|
documentation.
|
|
|
|
|
|
2015-03-07 18:36:07 +00:00
|
|
|
|
A few multimedia containers (MPEG-1, MPEG-2 PS, DV) allow one to concatenate
|
2013-01-24 13:04:59 +00:00
|
|
|
|
video by merely concatenating the files containing them.
|
2007-06-02 21:50:45 +00:00
|
|
|
|
|
|
|
|
|
Hence you may concatenate your multimedia files by first transcoding them to
|
|
|
|
|
these privileged formats, then using the humble @code{cat} command (or the
|
2007-06-04 21:09:38 +00:00
|
|
|
|
equally humble @code{copy} under Windows), and finally transcoding back to your
|
2007-06-02 21:50:45 +00:00
|
|
|
|
format of choice.
|
|
|
|
|
|
|
|
|
|
@example
|
2012-06-21 17:43:33 +00:00
|
|
|
|
ffmpeg -i input1.avi -qscale:v 1 intermediate1.mpg
|
|
|
|
|
ffmpeg -i input2.avi -qscale:v 1 intermediate2.mpg
|
2007-06-02 21:50:45 +00:00
|
|
|
|
cat intermediate1.mpg intermediate2.mpg > intermediate_all.mpg
|
2012-06-21 17:43:33 +00:00
|
|
|
|
ffmpeg -i intermediate_all.mpg -qscale:v 2 output.avi
|
2007-06-02 21:50:45 +00:00
|
|
|
|
@end example
|
|
|
|
|
|
2012-06-21 17:43:33 +00:00
|
|
|
|
Additionally, you can use the @code{concat} protocol instead of @code{cat} or
|
|
|
|
|
@code{copy} which will avoid creation of a potentially huge intermediate file.
|
2007-06-02 21:50:45 +00:00
|
|
|
|
|
2012-06-21 17:43:33 +00:00
|
|
|
|
@example
|
|
|
|
|
ffmpeg -i input1.avi -qscale:v 1 intermediate1.mpg
|
|
|
|
|
ffmpeg -i input2.avi -qscale:v 1 intermediate2.mpg
|
|
|
|
|
ffmpeg -i concat:"intermediate1.mpg|intermediate2.mpg" -c copy intermediate_all.mpg
|
|
|
|
|
ffmpeg -i intermediate_all.mpg -qscale:v 2 output.avi
|
|
|
|
|
@end example
|
|
|
|
|
|
|
|
|
|
Note that you may need to escape the character "|" which is special for many
|
|
|
|
|
shells.
|
|
|
|
|
|
|
|
|
|
Another option is usage of named pipes, should your platform support it:
|
2007-06-02 21:50:45 +00:00
|
|
|
|
|
|
|
|
|
@example
|
|
|
|
|
mkfifo intermediate1.mpg
|
|
|
|
|
mkfifo intermediate2.mpg
|
2012-06-21 17:43:33 +00:00
|
|
|
|
ffmpeg -i input1.avi -qscale:v 1 -y intermediate1.mpg < /dev/null &
|
|
|
|
|
ffmpeg -i input2.avi -qscale:v 1 -y intermediate2.mpg < /dev/null &
|
2007-06-02 21:50:45 +00:00
|
|
|
|
cat intermediate1.mpg intermediate2.mpg |\
|
2012-10-10 11:51:07 +00:00
|
|
|
|
ffmpeg -f mpeg -i - -c:v mpeg4 -acodec libmp3lame output.avi
|
2007-06-02 21:50:45 +00:00
|
|
|
|
@end example
|
|
|
|
|
|
2012-07-23 13:02:57 +00:00
|
|
|
|
@subsection Concatenating using raw audio and video
|
|
|
|
|
|
2007-06-02 21:50:45 +00:00
|
|
|
|
Similarly, the yuv4mpegpipe format, and the raw video, raw audio codecs also
|
|
|
|
|
allow concatenation, and the transcoding step is almost lossless.
|
2010-01-06 13:49:31 +00:00
|
|
|
|
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.
|
|
|
|
|
|
2012-07-23 12:35:10 +00:00
|
|
|
|
For example, let's say we want to concatenate two FLV files into an
|
|
|
|
|
output.flv file:
|
2007-06-02 21:50:45 +00:00
|
|
|
|
|
|
|
|
|
@example
|
|
|
|
|
mkfifo temp1.a
|
|
|
|
|
mkfifo temp1.v
|
|
|
|
|
mkfifo temp2.a
|
|
|
|
|
mkfifo temp2.v
|
|
|
|
|
mkfifo all.a
|
|
|
|
|
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 &
|
2010-01-06 13:49:31 +00:00
|
|
|
|
@{ ffmpeg -i input2.flv -an -f yuv4mpegpipe - < /dev/null | tail -n +2 > temp2.v ; @} &
|
2007-06-02 21:50:45 +00:00
|
|
|
|
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 \
|
|
|
|
|
-f yuv4mpegpipe -i all.v \
|
2012-10-09 15:40:20 +00:00
|
|
|
|
-y output.flv
|
2007-06-02 21:50:45 +00:00
|
|
|
|
rm temp[12].[av] all.[av]
|
|
|
|
|
@end example
|
|
|
|
|
|
2012-01-24 11:42:20 +00:00
|
|
|
|
@section Using @option{-f lavfi}, audio becomes mono for no apparent reason.
|
|
|
|
|
|
|
|
|
|
Use @option{-dumpgraph -} to find out exactly where the channel layout is
|
|
|
|
|
lost.
|
|
|
|
|
|
2013-04-11 16:23:18 +00:00
|
|
|
|
Most likely, it is through @code{auto-inserted aresample}. Try to understand
|
2012-01-24 11:42:20 +00:00
|
|
|
|
why the converting filter was needed at that place.
|
|
|
|
|
|
2012-01-24 15:03:09 +00:00
|
|
|
|
Just before the output is a likely place, as @option{-f lavfi} currently
|
2012-01-24 11:42:20 +00:00
|
|
|
|
only support packed S16.
|
|
|
|
|
|
2013-04-11 16:23:18 +00:00
|
|
|
|
Then insert the correct @code{aformat} explicitly in the filtergraph,
|
2012-01-24 11:42:20 +00:00
|
|
|
|
specifying the exact format.
|
|
|
|
|
|
|
|
|
|
@example
|
2013-04-11 16:23:18 +00:00
|
|
|
|
aformat=sample_fmts=s16:channel_layouts=stereo
|
2012-01-24 11:42:20 +00:00
|
|
|
|
@end example
|
|
|
|
|
|
2012-07-25 15:23:39 +00:00
|
|
|
|
@section Why does FFmpeg not see the subtitles in my VOB file?
|
|
|
|
|
|
|
|
|
|
VOB and a few other formats do not have a global header that describes
|
|
|
|
|
everything present in the file. Instead, applications are supposed to scan
|
|
|
|
|
the file to see what it contains. Since VOB files are frequently large, only
|
|
|
|
|
the beginning is scanned. If the subtitles happen only later in the file,
|
2014-06-03 02:46:04 +00:00
|
|
|
|
they will not be initially detected.
|
2012-07-25 15:23:39 +00:00
|
|
|
|
|
|
|
|
|
Some applications, including the @code{ffmpeg} command-line tool, can only
|
|
|
|
|
work with streams that were detected during the initial scan; streams that
|
|
|
|
|
are detected later are ignored.
|
|
|
|
|
|
|
|
|
|
The size of the initial scan is controlled by two options: @code{probesize}
|
|
|
|
|
(default ~5 Mo) and @code{analyzeduration} (default 5,000,000 µs = 5 s). For
|
|
|
|
|
the subtitle stream to be detected, both values must be large enough.
|
|
|
|
|
|
2012-11-07 22:45:12 +00:00
|
|
|
|
@section Why was the @command{ffmpeg} @option{-sameq} option removed? What to use instead?
|
2012-11-02 14:50:23 +00:00
|
|
|
|
|
|
|
|
|
The @option{-sameq} option meant "same quantizer", and made sense only in a
|
|
|
|
|
very limited set of cases. Unfortunately, a lot of people mistook it for
|
|
|
|
|
"same quality" and used it in places where it did not make sense: it had
|
|
|
|
|
roughly the expected visible effect, but achieved it in a very inefficient
|
|
|
|
|
way.
|
|
|
|
|
|
|
|
|
|
Each encoder has its own set of options to set the quality-vs-size balance,
|
|
|
|
|
use the options for the encoder you are using to set the quality level to a
|
|
|
|
|
point acceptable for your tastes. The most common options to do that are
|
|
|
|
|
@option{-qscale} and @option{-qmax}, but you should peruse the documentation
|
|
|
|
|
of the encoder you chose.
|
|
|
|
|
|
2015-02-09 15:17:22 +00:00
|
|
|
|
@section I have a stretched video, why does scaling does not fix it?
|
|
|
|
|
|
|
|
|
|
A lot of video codecs and formats can store the @emph{aspect ratio} of the
|
|
|
|
|
video: this is the ratio between the width and the height of either the full
|
|
|
|
|
image (DAR, display aspect ratio) or individual pixels (SAR, sample aspect
|
|
|
|
|
ratio). For example, EGA screens at resolution 640×350 had 4:3 DAR and 35:48
|
|
|
|
|
SAR.
|
|
|
|
|
|
|
|
|
|
Most still image processing work with square pixels, i.e. 1:1 SAR, but a lot
|
|
|
|
|
of video standards, especially from the analogic-numeric transition era, use
|
|
|
|
|
non-square pixels.
|
|
|
|
|
|
|
|
|
|
Most processing filters in FFmpeg handle the aspect ratio to avoid
|
|
|
|
|
stretching the image: cropping adjusts the DAR to keep the SAR constant,
|
|
|
|
|
scaling adjusts the SAR to keep the DAR constant.
|
|
|
|
|
|
|
|
|
|
If you want to stretch, or “unstretch”, the image, you need to override the
|
|
|
|
|
information with the
|
2016-10-22 18:12:30 +00:00
|
|
|
|
@url{ffmpeg-filters.html#setdar_002c-setsar, @code{setdar or setsar filters}}.
|
2015-02-09 15:17:22 +00:00
|
|
|
|
|
|
|
|
|
Do not forget to examine carefully the original video to check whether the
|
|
|
|
|
stretching comes from the image or from the aspect ratio information.
|
|
|
|
|
|
|
|
|
|
For example, to fix a badly encoded EGA capture, use the following commands,
|
|
|
|
|
either the first one to upscale to square pixels or the second one to set
|
|
|
|
|
the correct aspect ratio or the third one to avoid transcoding (may not work
|
|
|
|
|
depending on the format / codec / player / phase of the moon):
|
|
|
|
|
|
|
|
|
|
@example
|
|
|
|
|
ffmpeg -i ega_screen.nut -vf scale=640:480,setsar=1 ega_screen_scaled.nut
|
|
|
|
|
ffmpeg -i ega_screen.nut -vf setdar=4/3 ega_screen_anamorphic.nut
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ffmpeg -i ega_screen.nut -aspect 4/3 -c copy ega_screen_overridden.nut
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@end example
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2002-11-04 18:50:04 +00:00
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@chapter Development
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2011-03-17 15:55:58 +00:00
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@section Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat?
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2003-07-22 13:08:52 +00:00
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2012-08-21 18:07:06 +00:00
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Yes. Check the @file{doc/examples} directory in the source
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repository, also available online at:
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@url{https://github.com/FFmpeg/FFmpeg/tree/master/doc/examples}.
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Examples are also installed by default, usually in
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@code{$PREFIX/share/ffmpeg/examples}.
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Also you may read the Developers Guide of the FFmpeg documentation. Alternatively,
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2005-12-17 18:14:38 +00:00
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examine the source code for one of the many open source projects that
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2011-03-17 15:55:58 +00:00
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already incorporate FFmpeg at (@url{projects.html}).
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2003-07-22 13:08:52 +00:00
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2007-06-21 05:14:00 +00:00
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@section Can you support my C compiler XXX?
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2002-11-04 18:50:04 +00:00
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2007-01-25 17:34:08 +00:00
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It depends. If your compiler is C99-compliant, then patches to support
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it are likely to be welcome if they do not pollute the source code
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with @code{#ifdef}s related to the compiler.
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2002-11-04 18:50:04 +00:00
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2007-11-09 14:05:43 +00:00
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@section Is Microsoft Visual C++ supported?
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2007-02-05 16:38:47 +00:00
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2012-09-27 19:02:28 +00:00
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Yes. Please see the @uref{platform.html, Microsoft Visual C++}
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section in the FFmpeg documentation.
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2007-02-05 16:45:36 +00:00
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2007-06-21 05:14:00 +00:00
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@section Can you add automake, libtool or autoconf support?
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2002-11-04 18:50:04 +00:00
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2007-01-25 17:34:08 +00:00
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No. These tools are too bloated and they complicate the build.
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2002-11-04 18:50:04 +00:00
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2011-12-10 23:40:09 +00:00
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@section Why not rewrite FFmpeg in object-oriented C++?
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2004-07-15 21:28:18 +00:00
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2011-03-17 15:55:58 +00:00
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FFmpeg is already organized in a highly modular manner and does not need to
|
2005-12-17 18:14:38 +00:00
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be rewritten in a formal object language. Further, many of the developers
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2004-10-01 02:35:21 +00:00
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favor straight C; it works for them. For more arguments on this matter,
|
2011-07-08 13:33:17 +00:00
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read @uref{http://www.tux.org/lkml/#s15, "Programming Religion"}.
|
2004-10-01 02:35:21 +00:00
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2007-06-21 05:14:00 +00:00
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@section Why are the ffmpeg programs devoid of debugging symbols?
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2004-10-01 02:35:21 +00:00
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|
2013-09-24 19:43:19 +00:00
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The build process creates @command{ffmpeg_g}, @command{ffplay_g}, etc. which
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contain full debug information. Those binaries are stripped to create
|
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@command{ffmpeg}, @command{ffplay}, etc. If you need the debug information, use
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the *_g versions.
|
2004-07-15 21:28:18 +00:00
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2007-06-21 05:14:00 +00:00
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@section I do not like the LGPL, can I contribute code under the GPL instead?
|
2005-09-11 16:39:47 +00:00
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2005-09-12 15:51:29 +00:00
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Yes, as long as the code is optional and can easily and cleanly be placed
|
2011-11-29 16:50:25 +00:00
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under #if CONFIG_GPL without breaking anything. So, for example, a new codec
|
2008-06-06 07:51:36 +00:00
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or filter would be OK under GPL while a bug fix to LGPL code would not.
|
2005-09-11 16:39:47 +00:00
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|
2012-07-11 10:01:19 +00:00
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@section I'm using FFmpeg from within my C application but the linker complains about missing symbols from the libraries themselves.
|
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FFmpeg builds static libraries by default. In static libraries, dependencies
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|
are not handled. That has two consequences. First, you must specify the
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libraries in dependency order: @code{-lavdevice} must come before
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@code{-lavformat}, @code{-lavutil} must come after everything else, etc.
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|
Second, external libraries that are used in FFmpeg have to be specified too.
|
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|
An easy way to get the full list of required libraries in dependency order
|
|
|
|
|
is to use @code{pkg-config}.
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|
|
@example
|
2013-09-24 19:42:21 +00:00
|
|
|
|
c99 -o program program.c $(pkg-config --cflags --libs libavformat libavcodec)
|
2012-07-11 10:01:19 +00:00
|
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|
@end example
|
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|
See @file{doc/example/Makefile} and @file{doc/example/pc-uninstalled} for
|
|
|
|
|
more details.
|
|
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|
|
|
2011-12-10 23:40:09 +00:00
|
|
|
|
@section I'm using FFmpeg from within my C++ application but the linker complains about missing symbols which seem to be available.
|
2007-07-27 13:40:02 +00:00
|
|
|
|
|
2011-03-17 15:55:58 +00:00
|
|
|
|
FFmpeg is a pure C project, so to use the libraries within your C++ application
|
2007-07-27 13:40:02 +00:00
|
|
|
|
you need to explicitly state that you are using a C library. You can do this by
|
2011-03-17 15:55:58 +00:00
|
|
|
|
encompassing your FFmpeg includes using @code{extern "C"}.
|
2007-07-27 13:40:02 +00:00
|
|
|
|
|
|
|
|
|
See @url{http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html#faq-32.3}
|
|
|
|
|
|
2011-09-10 14:23:50 +00:00
|
|
|
|
@section I'm using libavutil from within my C++ application but the compiler complains about 'UINT64_C' was not declared in this scope
|
|
|
|
|
|
2011-12-08 19:07:32 +00:00
|
|
|
|
FFmpeg is a pure C project using C99 math features, in order to enable C++
|
2011-09-10 14:23:50 +00:00
|
|
|
|
to use them you have to append -D__STDC_CONSTANT_MACROS to your CXXFLAGS
|
|
|
|
|
|
2008-03-12 23:58:46 +00:00
|
|
|
|
@section I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat?
|
2006-05-18 08:01:47 +00:00
|
|
|
|
|
2012-10-07 21:19:29 +00:00
|
|
|
|
You have to create a custom AVIOContext using @code{avio_alloc_context},
|
2012-10-12 12:15:33 +00:00
|
|
|
|
see @file{libavformat/aviobuf.c} in FFmpeg and @file{libmpdemux/demux_lavf.c} in MPlayer or MPlayer2 sources.
|
2006-05-18 08:01:47 +00:00
|
|
|
|
|
2007-04-04 11:41:13 +00:00
|
|
|
|
@section Where is the documentation about ffv1, msmpeg4, asv1, 4xm?
|
2007-03-20 21:12:06 +00:00
|
|
|
|
|
2015-10-08 01:40:53 +00:00
|
|
|
|
see @url{https://www.ffmpeg.org/~michael/}
|
2007-03-20 21:12:06 +00:00
|
|
|
|
|
2007-09-13 13:45:49 +00:00
|
|
|
|
@section How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?
|
2007-07-15 12:17:05 +00:00
|
|
|
|
|
2007-07-17 14:15:39 +00:00
|
|
|
|
Even if peculiar since it is network oriented, RTP is a container like any
|
2007-07-17 14:59:29 +00:00
|
|
|
|
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.
|
2007-07-15 12:17:05 +00:00
|
|
|
|
|
2011-11-29 16:50:25 +00:00
|
|
|
|
@section AVStream.r_frame_rate is wrong, it is much larger than the frame rate.
|
2007-09-11 10:25:34 +00:00
|
|
|
|
|
2013-09-24 19:41:21 +00:00
|
|
|
|
@code{r_frame_rate} is NOT the average frame rate, it is the smallest frame rate
|
2007-09-13 13:45:49 +00:00
|
|
|
|
that can accurately represent all timestamps. So no, it is not
|
|
|
|
|
wrong if it is larger than the average!
|
2013-09-24 19:41:21 +00:00
|
|
|
|
For example, if you have mixed 25 and 30 fps content, then @code{r_frame_rate}
|
|
|
|
|
will be 150 (it is the least common multiple).
|
|
|
|
|
If you are looking for the average frame rate, see @code{AVStream.avg_frame_rate}.
|
2007-09-11 10:25:34 +00:00
|
|
|
|
|
2011-12-30 22:14:14 +00:00
|
|
|
|
@section Why is @code{make fate} not running all tests?
|
|
|
|
|
|
|
|
|
|
Make sure you have the fate-suite samples and the @code{SAMPLES} Make variable
|
|
|
|
|
or @code{FATE_SAMPLES} environment variable or the @code{--samples}
|
|
|
|
|
@command{configure} option is set to the right path.
|
|
|
|
|
|
|
|
|
|
@section Why is @code{make fate} not finding the samples?
|
|
|
|
|
|
|
|
|
|
Do you happen to have a @code{~} character in the samples path to indicate a
|
|
|
|
|
home directory? The value is used in ways where the shell cannot expand it,
|
|
|
|
|
causing FATE to not find files. Just replace @code{~} by the full path.
|
|
|
|
|
|
2002-11-04 18:50:04 +00:00
|
|
|
|
@bye
|