For codecs where decoding of a whole plane can simply
be skipped, we should offer applications to not decode
alpha for better performance (ca. 30% less CPU usage
and 40% reduced memory bandwidth).
It also means applications do not need to implement support
(even if it is rather simple) for YUVA formats in order to be
able to play these files.
Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
avcodec_find_best_pix_fmt2 does not modify its first argument so may be
marked const. This avoids a warning when passing in AVCodec.pix_fmts.
Signed-off-by: Dylan Simon <dylan@dylex.net>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
"Fork" is an ambiguous term, since there may be more than one fork, also
"fork" could be confused with the corresponding function. Also it seems
important to point the name of the referenced fork in the symbol.
Note: the old --enable-incompatible-fork-abi command is retained for
compatibility, although it should be considered deprecated.
Currently the WebVTT demuxer parses the cues but throws away
the cue id (the optional first line of the cue) and cue
settings (the optional rendering instructions that follow
the timestamp).
However, in order to write inband text tracks (to WebM
files), the entire cue payload from the WebVTT source must
be preserved.
This commit makes no change to the data part of the output
buffer packet (where the actual cue text is stored), but
does add the cue id and settings as a side data items, if
they're present in the cue. Existing code that cares only
about the data part of the packet can continue to ignore the
side data.
There are two new packet data type flags,
AV_PKT_DATA_WEBVTT_IDENTIFIER and
AV_PKT_DATA_WEBVTT_SETTINGS.
Some fixes provided by Paul B Mahol <onemda@gmail.com>
and Michael Niedermayer <michaelni@gmx.at> and me.
Signed-off-by: Diego Biurrun <diego@biurrun.de>
Signed-off-by: Kostya Shishkov <kostya.shishkov@gmail.com>
Refactoring copy_side_data into a separate function so that it can be called
in cases where side data needs to be duplicated.
Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Based on the 2007 GSoC project from Kamil Nowosad <k.nowosad@students.mimuw.edu.pl>
Updated to current programming standards, style and many more small
fixes by Diego Biurrun <diego@biurrun.de>.
Signed-off-by: Diego Biurrun <diego@biurrun.de>
Currently, we have a AV_CODEC_ID_SSA, which matches the way the ASS/SSA
markup is muxed in a standalone .ass/.ssa file. This means the AVPacket
data starts with a "Dialogue:" string, followed by a timing information
(start and end of the event as string) and a trailing CRLF after each
line. One packet can contain several lines. We'll refer to this layout
as "SSA" or "SSA lines".
In matroska, this markup is not stored as such: it has no "Dialogue:"
prefix, it contains a ReadOrder field, the timing information is not in
the payload, and it doesn't contain the trailing CRLF. See [1] for more
info. We'll refer to this layout as "ASS".
Since we have only one common codec for both formats, the matroska
demuxer is constructing an AVPacket following the "SSA lines" format.
This causes several problems, so it was decided to change this into
clean ASS packets.
Some insight about what is changed or unchanged in this commit:
CODECS
------
- the decoding process still writes "SSA lines" markup inside the ass
fields of the subtitles rectangles (sub->rects[n]->ass), which is
still the current common way of representing decoded subtitles
markup. It is meant to change later.
- new ASS codec id: AV_CODEC_ID_ASS (which is different from the
legacy AV_CODEC_ID_SSA)
- lavc/assdec: the "ass" decoder is renamed into "ssa" (instead of
"ass") for consistency with the codec id and allows to add a real
ass decoder. This ass decoder receives clean ASS lines (so it starts
with a ReadOrder, is followed by the Layer, etc). We make sure this
is decoded properly in a new ass-line rectangle of the decoded
subtitles (the ssa decoder OTOH is doing a simple straightforward
copy). Using the packet timing instead of data string makes sure the
ass-line now contains the appropriate timing.
- lavc/assenc: just like the ass decoder, the "ssa" encoder is renamed
into "ssa" (instead of "ass") for consistency with the codec id, and
allows to add a real "ass" encoder.
One important thing about this encoder is that it only supports one
ass rectangle: we could have put several dialogue events in the
AVPacket (separated by a \0 for instance) but this would have cause
trouble for the muxer which needs not only the start time, but also
the duration: typically, you have merged events with the same start
time (stored in the AVPacket->pts) but a different duration. At the
moment, only the matroska do the merge with the SSA-line codec.
We will need to make sure all the decoders in the future can't add
more than one rectangle (and only one Dialogue line in it
obviously).
FORMATS
-------
- lavf/assenc: the .ass/.ssa muxer can take both SSA and ASS packets.
In the case of ASS packets as input, it adds the timing based on the
AVPacket pts and duration, and mux it with "Dialogue:", trailing
CRLF, etc.
- lavf/assdec: unchanged; it currently still only outputs SSA-lines
packets.
- lavf/mkv: the demuxer can now output ASS packets without the need of
any "SSA-lines" reconstruction hack. It will become the default at
next libavformat bump, and the SSA support will be dropped from the
demuxer. The muxer can take ASS packets since it's muxed normally,
and still supports the old SSA packets. All the SSA support and
hacks in Matroska code will be dropped at next lavf bump.
[1]: http://www.matroska.org/technical/specs/subtitles/ssa.html
Anton Khirnov
Paul B Mahol
Michael Niedermayer
Reimar Döffinger
Justin Ruggles
Dylan Alex Simon
Michael Bradshaw
Diego Biurrun
Clément Bœsch
Dirk Farin
Luca Barbato
Kostya Shishkov
Rémi Denis-Courmont
Yusuke Nakamura
Stefano Sabatini
Kieran Kunhya
Clément Bœsch
Matthew Heaney
Ash Hughes
Eli Friedman
Vignesh Venkatasubramanian
James Almer
Masaki Tanaka
Derek Buitenhuis
Nicolas Bertrand