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.
Currently it is broken when explicitly using the file protocol, it uses an
insecure temporary file name, and in commit b4431c80 disabling the option by
default was already considered. Also it is not very consistent to have such an
option for one particular muxer.
Signed-off-by: Marton Balint <cus@passwd.hu>
Libav, for some reason, merged this as a public API function. This will
aid in future merges.
A define is left for backwards compat, just in case some person
used it, since it is in a public header.
Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Some (de)muxers open additional files beyond the main IO context.
Currently, they call avio_open() directly, which prevents the caller
from using custom IO for such streams.
This commit adds callbacks to AVFormatContext that default to
avio_open2()/avio_close(), but can be overridden by the caller. All
muxers and demuxers using AVIO are switched to using those callbacks
instead of calling avio_open()/avio_close() directly.
(de)muxers that use the URLProtocol layer directly instead of AVIO
remain unconverted for now. This should be fixed in later commits.
For protocols other than local files ff_rename() is not implemented
For split planes support the implementation is simply wrong
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
Allows avformat_query_codec to be used to check for valid image2 encoders.
Reuses the existing ff_guess_image2_codec ID table.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
Michael Niedermayer
rogerdpack
Luca Barbato
Anton Khirnov
Marton Balint
Derek Buitenhuis
Clément Bœsch
Hendrik Leppkes
tab
Diego Biurrun
Michael Niedermayer
Carl Eugen Hoyos
Vittorio Giovara
Jean First
Justin Ruggles
Clément Bœsch
Stefano Sabatini
Ramiro Polla
Clément Bœsch
Paul B Mahol
Martin Storsjö