[FFmpeg-devel] [PATCH] matroska: Set CodecDelay and SeekPreroll in the AVStream

Michael Niedermayer michaelni at gmx.at
Tue Sep 24 12:53:14 CEST 2013


On Mon, Sep 23, 2013 at 04:03:25PM -0700, Vignesh Venkatasubramanian wrote:
> On Mon, Sep 23, 2013 at 4:02 PM, Vignesh Venkatasubramanian
> <vigneshv at google.com> wrote:
> > This patch exports the values of Codec Delay and Seek Preroll
> > container elements as in the AVStream structure. The seek_preroll
> > field has been added to the AVStream struct and the minor version
> > of libavformat has been bumped.
> >
> > Signed-off-by: Vignesh Venkatasubramanian <vigneshv at google.com>
> > ---
> >  libavformat/avformat.h    | 16 ++++++++++++++++
> >  libavformat/matroskadec.c | 14 ++++++++++++++
> >  libavformat/version.h     |  2 +-
> >  3 files changed, 31 insertions(+), 1 deletion(-)
> >
> > diff --git a/libavformat/avformat.h b/libavformat/avformat.h
> > index b18eb3f..6671a83 100644
> > --- a/libavformat/avformat.h
> > +++ b/libavformat/avformat.h
> > @@ -856,6 +856,9 @@ typedef struct AVStream {
> >
> >      /**
> >       * Number of samples to skip at the start of the frame decoded from the next packet.
> > +     *
> > +     * Code outside avformat should access this field using:
> > +     * av_stream_get_skip_samples/set_skip_samples(stream)
> >       */
> >      int skip_samples;

when does code outside lavf need to access this ?


> >
> > @@ -888,10 +891,23 @@ typedef struct AVStream {
> >       */
> >      int pts_wrap_behavior;
> >
> > +    /**
> > +     * Number of samples to skip after a discontinuity. For example, when a seek
> > +     * happens.
> > +     *
> > +     * Code outside avformat should access this field using:
> > +     * av_stream_get/set_seek_preroll(stream)
> > +     */
> > +    int seek_preroll;
> > +
> >  } AVStream;
> >
> >  AVRational av_stream_get_r_frame_rate(const AVStream *s);
> >  void       av_stream_set_r_frame_rate(AVStream *s, AVRational r);
> > +int  av_stream_get_skip_samples(const AVStream *s);
> > +void av_stream_set_skip_samples(AVStream *s, int skip_samples);
> > +int  av_stream_get_seek_preroll(const AVStream *s);
> > +void av_stream_set_seek_preroll(AVStream *s, int seek_preroll);
> >
> >  #define AV_PROGRAM_RUNNING 1
> >
> > diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
> > index a1b7f56..ecbc723 100644
> > --- a/libavformat/matroskadec.c
> > +++ b/libavformat/matroskadec.c
> > @@ -163,6 +163,8 @@ typedef struct {
> >      uint64_t default_duration;
> >      uint64_t flag_default;
> >      uint64_t flag_forced;
> > +    uint64_t codec_delay;
> > +    uint64_t seek_preroll;
> >      MatroskaTrackVideo video;
> >      MatroskaTrackAudio audio;
> >      MatroskaTrackOperation operation;
> > @@ -410,6 +412,8 @@ static EbmlSyntax matroska_track[] = {
> >      { MATROSKA_ID_TRACKOPERATION,       EBML_NEST, 0, offsetof(MatroskaTrack,operation), {.n=matroska_track_operation} },
> >      { MATROSKA_ID_TRACKCONTENTENCODINGS,EBML_NEST, 0, 0, {.n=matroska_track_encodings} },
> >      { MATROSKA_ID_TRACKMAXBLKADDID,     EBML_UINT, 0, offsetof(MatroskaTrack,max_block_additional_id) },
> > +    { MATROSKA_ID_CODECDELAY,           EBML_UINT, 0, offsetof(MatroskaTrack,codec_delay) },
> > +    { MATROSKA_ID_SEEKPREROLL,          EBML_UINT, 0, offsetof(MatroskaTrack,seek_preroll) },
> >      { MATROSKA_ID_TRACKFLAGENABLED,     EBML_NONE },
> >      { MATROSKA_ID_TRACKFLAGLACING,      EBML_NONE },
> >      { MATROSKA_ID_CODECNAME,            EBML_NONE },

> > @@ -1874,6 +1878,16 @@ static int matroska_read_header(AVFormatContext *s)
> >              st->codec->bits_per_coded_sample = track->audio.bitdepth;
> >              if (st->codec->codec_id != AV_CODEC_ID_AAC)
> >              st->need_parsing = AVSTREAM_PARSE_HEADERS;
> > +            if (track->codec_delay > 0) {
> > +                st->skip_samples = av_rescale_q(track->codec_delay,
> > +                                                (AVRational){1, 1000000000},
> > +                                                (AVRational){1, st->codec->sample_rate});
> > +            }

i suspect this alone wont work when the user seeks back to the first
packet
also the addition of seek_preroll to the core and changing
skip_samples in matroskadec could be in seperate patches (would also
simplify future debugability with bisect)


> > +            if (track->seek_preroll > 0) {
> > +                st->seek_preroll = av_rescale_q(track->seek_preroll,
> > +                                                (AVRational){1, 1000000000},
> > +                                                (AVRational){1, st->codec->sample_rate});
> > +            }
> >          } else if (codec_id == AV_CODEC_ID_WEBVTT) {
> >              st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
> >
> > diff --git a/libavformat/version.h b/libavformat/version.h
> > index c224232..ff38e96 100644
> > --- a/libavformat/version.h
> > +++ b/libavformat/version.h
> > @@ -30,7 +30,7 @@
> >  #include "libavutil/avutil.h"
> >
> >  #define LIBAVFORMAT_VERSION_MAJOR 55
> > -#define LIBAVFORMAT_VERSION_MINOR 18
> > +#define LIBAVFORMAT_VERSION_MINOR 19
> >  #define LIBAVFORMAT_VERSION_MICRO 102
> 
> I am unsure if i should reset the micro version while bumping the
> minor version. Looking at
> older patches suggests that i shouldn't. Please let me know if i'm
> wrong. Thanks.

micro should be reset to 100 when minor or major is bumped

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Into a blind darkness they enter who follow after the Ignorance,
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