The libavformat API is not suitable for exporting output devices as muxers.
Some practical problems are e.g. lack of timing/synchronization mechanisms
or interaction with output-specific features.
Currently, AVStream contains an embedded AVCodecContext instance, which
is used by demuxers to export stream parameters to the caller and by
muxers to receive stream parameters from the caller. It is also used
internally as the codec context that is passed to parsers.
In addition, it is also widely used by the callers as the decoding (when
demuxer) or encoding (when muxing) context, though this has been
officially discouraged since Libav 11.
There are multiple important problems with this approach:
- the fields in AVCodecContext are in general one of
* stream parameters
* codec options
* codec state
However, it's not clear which ones are which. It is consequently
unclear which fields are a demuxer allowed to set or a muxer allowed to
read. This leads to erratic behaviour depending on whether decoding or
encoding is being performed or not (and whether it uses the AVStream
embedded codec context).
- various synchronization issues arising from the fact that the same
context is used by several different APIs (muxers/demuxers,
parsers, bitstream filters and encoders/decoders) simultaneously, with
there being no clear rules for who can modify what and the different
processes being typically delayed with respect to each other.
- avformat_find_stream_info() making it necessary to support opening
and closing a single codec context multiple times, thus
complicating the semantics of freeing various allocated objects in the
codec context.
Those problems are resolved by replacing the AVStream embedded codec
context with a newly added AVCodecParameters instance, which stores only
the stream parameters exported by the demuxers or read by the muxers.
It makes more sense for a bit mask to use an unsigned type.
The change should be source and binary compatible on all
supported systems, hence micro version bump.
Fixes a few invalid shifts.
Signed-off-by: Mans Rullgard <mans@mansr.com>
In testing, the file output plugin gave a max buffer size of about 20 million
frames, which is way more than what is really needed and causes a memory
allocation error on my system.
Currently quad, 5.0, 5.1 and 7.1 are implemented.
Implementing support for other formats/layouts and capture should be
straightforward.
5.0 and 7.1 support by Carl Eugen Hoyos.
Signed-off-by: Anton Khirnov <anton@khirnov.net>
Passing an explicit filename to this command is only necessary if the
documentation in the @file block refers to a file different from the
one the block resides in.
Originally committed as revision 22921 to svn://svn.ffmpeg.org/ffmpeg/trunk
This avoids symbol redefinitions problems, for example avoids the "free"
symbol to be redefined before system headers actually using it are
included, thus breaking compilation. In particular this change allows
to build FFmpeg with salsa.
Patch by matthieu castet <$surname.mat?hieu@free fr>.
Originally committed as revision 20665 to svn://svn.ffmpeg.org/ffmpeg/trunk
Otherwise doxygen complains about ambiguous filenames when files exist
under the same name in different subdirectories.
Originally committed as revision 16912 to svn://svn.ffmpeg.org/ffmpeg/trunk
Patch by Nicolas George: name surname normalesup org
Original thread: [FFmpeg-devel] [PATCH] ALSA for libavdevice
Date: 12/09/2008 07:17 PM
Originally committed as revision 16800 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diego Biurrun
Anton Khirnov
Justin Ruggles
Mans Rullgard
Nicolas George
Carl Eugen Hoyos
Stefano Sabatini
Matthieu Castet
Carl Eugen Hoyos
Luca Abeni
Nicolas George