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.
The rationale is that coded_frame was only used to communicate key_frame,
pict_type and quality to the caller, as well as a few other random fields,
in a non predictable, let alone consistent way.
There was agreement that there was no use case for coded_frame, as it is
a full-sized AVFrame container used for just 2-3 int-sized properties,
which shouldn't even belong into the AVCodecContext in the first place.
The appropriate AVPacket flag can be used instead of key_frame, while
quality is exported with the new AVPacketSideData quality factor.
There is no replacement for the other fields as they were unreliable,
mishandled or just not used at all.
Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>
Incidentally `-y` also collides with avconv global options.
Update x11grab to match and document the option.
CC: libav-stable@libav.org
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
The feature is implemented using a transparent window and drawing
inside it a rectangle filling the whole window to highlight it.
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
Also add a note about SNDCTL_DSP_GETFMTS which may fail even if OSS is
available.
CC: libav-stable@libav.org
Bug-Id: CID 1238992
Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>
The paint_mouse_pointer() code uses XFixes to retrieve the cursor
coordinates, but XFixes gives no information about which screen the
pointer is on; this results in always drawing the cursor on the
captured screen even if the mouse pointer was on another screen.
For example, when capturing from screen 1 (i.e. -f x11grab -i ":0.1")
the cursor was being drawn in the captured image even when the mouse
pointer was actually on screen 0, which is wrong and visually confusing.
CC: libav-stable@libav.org
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
