Commit Graph

10 Commits

Author SHA1 Message Date
Clément Bœsch
7c1a002c78 subtitles: introduce ASS codec id and use it.
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
2013-04-18 23:23:59 +02:00
Lou Logan
6851130fd6 cosmetics: minor libavcodec spelling errors
Also update some common misspelled words in patcheck

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
2012-06-29 14:54:15 +02:00
Clément Bœsch
d51e08bb89 lavc: switch from ts_end to duration in ff_ass_add_rect.
Make possible a end-to-presentation duration.
2012-05-29 21:33:28 +02:00
Michael Niedermayer
cbfdfbe846 Merge remote-tracking branch 'qatar/master'
* qatar/master:
  ARM: ac3: update ff_ac3_extract_exponents_neon per 8b7b2d6
  ARM: NEON optimised vector_clip_int32()
  swscale: disable full_chroma_int when converting to non-24/32bpp RGB.
  suggest to use av_get_bytes_per_sample() in av_get_bits_per_sample_format() doxy
  ffmpeg: use av_get_bytes_per_sample() in place of av_get_bits_per_sample_fmt()
  put_bits: remove ALT_BITSTREAM_WRITER
  put_bits: always use intreadwrite.h macros
  libavformat: Add an example how to use the metadata API
  doxygen: Prefer member groups over grouping into modules
  doxygen: be more permissive when searching for API examples
  avformat: doxify the Metadata API
  lavf: restore old behavior for custom AVIOContex with an AVFMT_NOFILE format.
  lavf: use the correct pointer in av_open_input_stream().
  avidec: infer absolute vs relative index from first packet

Conflicts:
	libavformat/Makefile
	libavformat/avidec.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
2011-07-03 03:14:10 +02:00
Reinhard Tartler
21a19b7912 doxygen: Prefer member groups over grouping into modules
Before this, almost all module groups have been used for grouping functions
and fields in structures semantically. This causes them to not appear
properly in the file documentation and needlessly clutters up the "Modules"
index.

Additionally, this commit streamlines some spelling and appearances.
2011-07-02 13:52:29 +02:00
Aurelien Jacobs
3ee8ca9b08 add avcodec_get_subtitle_defaults() to initialize AVSubtitle struct
Call this new function before decode() to replace the custom and
inconsistant initialization in various decoders.
This function is equivalent to avcodec_get_frame_defaults() for AVFrame.

Signed-off-by: Aurelien Jacobs <aurel@gnuage.org>
2011-04-11 23:27:50 +02:00
Mans Rullgard
2912e87a6c Replace FFmpeg with Libav in licence headers
Signed-off-by: Mans Rullgard <mans@mansr.com>
2011-03-19 13:33:20 +00:00
Diego Elio Pettenò
cf1d794a49 Make ff_ass_subtitle_header static to ass.c
Signed-off-by: Janne Grunau <janne-ffmpeg@jannau.net>
2011-01-25 22:05:12 +01:00
Aurelien Jacobs
2c77c90684 add SubRip decoder
Originally committed as revision 26119 to svn://svn.ffmpeg.org/ffmpeg/trunk
2010-12-28 23:52:53 +00:00
Aurelien Jacobs
5952be07dc add missing files in previous commit (ASS encoder and decoder)
Originally committed as revision 25747 to svn://svn.ffmpeg.org/ffmpeg/trunk
2010-11-13 14:18:59 +00:00