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.
Also fix typo found by Lou Logan:
Sacrifying -> Sacrificing
Reviewed-by: Lou Logan <lou@lrcd.com>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
Don't trust provided streams.
Return with error when stream count is not 1 or
provided stream is not an audio stream.
Signed-off-by: Lukasz Marek <lukasz.m.luki@gmail.com>
Current implementation didn't include duration of
last processed packet.
Device may return negative timestamps without
this correction.
Signed-off-by: Lukasz Marek <lukasz.m.luki@gmail.com>
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>
Currently, only S16 quad, 5.1 and 7.1 are implemented.
Implementing support for other formats/layouts and capture should be
straightforward.
7.1 support by Carl Eugen Hoyos.
This also lists the objects from those two libraries as internal (by adding
the ff_ prefix) so that they can then be hidden via linker scripts.
(cherry picked from commit c6610a216e)
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
Jun Zhao
Diego Biurrun
Muhammad Faiz
Anton Khirnov
Andreas Cadhalpun
Lukasz Marek
Lukasz Marek
Nicolas George
Michael Niedermayer
Clément Bœsch
Nicolas George
Stefano Sabatini
Mans Rullgard
Diego Elio Pettenò
Matthieu Castet
Ivo van Poorten
Daniel Verkamp
Nicolas George