The DSS demuxer currently decrements a counter that should be positive
at the beginning of read_packet; should it become negative, it means
that the data to be read can't be read contiguosly, but has to be read
in two parts. In this case the counter is incremented again after the
first read if said read succeeded; if not, the counter stays negative.
This can lead to problems in further read_packet calls; in tickets #9020
and #9023 it led to segfaults if one tries to seek lateron if the seek
failed and generic seek tried to read from the beginning. But it could
also happen when av_new_packet() failed and the user attempted to read
again afterwards.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Put a buffer with a known fixed size into the demuxer's context instead
of allocating it separately. This also allows to remove the demuxer's
read_close()-function.
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Since bae8844e the packet will always be unreferenced when a demuxer
returns an error, so that a lot of calls to av_packet_unref() in lots of
demuxers are now redundant and can be removed.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Marton Balint <cus@passwd.hu>
Both attributes.h and bswap.h have been included from the very beginning
of this muxer without there being any reason to do so.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
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.
This assumes CBR (which is true for all samples i have)
Previous version reviewed by: Oleksij Rempel <linux@rempel-privat.de>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
