[FFmpeg-devel] [PATCH] libavformat/matroska: Write stream durations in metadata, in the format of mkvmerge.

[Michael Niedermayer]

On Tue, Aug 04, 2015 at 05:32:51PM -0700, Sasi Inguva wrote:
> Compute individual stream durations in matroska muxer.
> Write them as string tags in the same format as mkvmerge tool does.
> 
> Signed-off-by: Sasi Inguva <isasi at google.com>
> ---
>  libavformat/matroskaenc.c    | 75 +++++++++++++++++++++++++++++++++++++++++---
>  tests/fate/wavpack.mak       |  4 +--
>  tests/ref/acodec/tta         |  4 +--
>  tests/ref/fate/binsub-mksenc |  2 +-
>  tests/ref/lavf/mkv           |  8 ++---
>  tests/ref/seek/lavf-mkv      | 44 +++++++++++++-------------
>  6 files changed, 101 insertions(+), 36 deletions(-)
> 
> diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
> index 2d0d5f6..0d3ae37 100644
> --- a/libavformat/matroskaenc.c
> +++ b/libavformat/matroskaenc.c
> @@ -44,6 +44,7 @@
>  #include "libavutil/mathematics.h"
>  #include "libavutil/opt.h"
>  #include "libavutil/random_seed.h"
> +#include "libavutil/rational.h"
>  #include "libavutil/samplefmt.h"
>  #include "libavutil/sha.h"
>  #include "libavutil/stereo3d.h"
> @@ -131,6 +132,9 @@ typedef struct MatroskaMuxContext {
>  
>      int64_t last_track_timestamp[MAX_TRACKS];
>  
> +    int64_t* stream_durations;
> +    int64_t* stream_duration_offsets;
> +
>      int allow_raw_vfw;
>  } MatroskaMuxContext;
>  
> @@ -1151,12 +1155,12 @@ static int mkv_write_simpletag(AVIOContext *pb, AVDictionaryEntry *t)
>      return 0;
>  }
>  
> -static int mkv_write_tag(AVFormatContext *s, AVDictionary *m, unsigned int elementid,
> -                         unsigned int uid, ebml_master *tags)
> +static int mkv_write_tag_targets(AVFormatContext *s,
> +                                 unsigned int elementid, unsigned int uid,
> +                                 ebml_master *tags, ebml_master* tag)
>  {
>      MatroskaMuxContext *mkv = s->priv_data;
> -    ebml_master tag, targets;
> -    AVDictionaryEntry *t = NULL;
> +    ebml_master targets;
>      int ret;
>  
>      if (!tags->pos) {
> @@ -1166,11 +1170,24 @@ static int mkv_write_tag(AVFormatContext *s, AVDictionary *m, unsigned int eleme
>          *tags = start_ebml_master(s->pb, MATROSKA_ID_TAGS, 0);
>      }
>  
> -    tag     = start_ebml_master(s->pb, MATROSKA_ID_TAG,        0);
> +    *tag     = start_ebml_master(s->pb, MATROSKA_ID_TAG,        0);
>      targets = start_ebml_master(s->pb, MATROSKA_ID_TAGTARGETS, 0);
>      if (elementid)
>          put_ebml_uint(s->pb, elementid, uid);
>      end_ebml_master(s->pb, targets);
> +    return 0;
> +}
> +
> +static int mkv_write_tag(AVFormatContext *s, AVDictionary *m, unsigned int elementid,
> +                         unsigned int uid, ebml_master *tags)
> +{
> +    ebml_master tag;
> +    int ret;
> +    AVDictionaryEntry *t = NULL;
> +
> +    ret = mkv_write_tag_targets(s, elementid, uid, tags, &tag);
> +    if (ret < 0)
> +        return ret;
>  
>      while ((t = av_dict_get(m, "", t, AV_DICT_IGNORE_SUFFIX))) {
>          if (av_strcasecmp(t->key, "title") &&
> @@ -1220,6 +1237,29 @@ static int mkv_write_tags(AVFormatContext *s)
>          if (ret < 0) return ret;
>      }
>  
> +
> +    mkv->stream_durations = av_mallocz(s->nb_streams * sizeof(int64_t));
> +    mkv->stream_duration_offsets = av_mallocz(s->nb_streams * sizeof(int64_t));

this is not called in all cases, for example its not called for
webm


> +
> +    if (!mkv->is_live) {
> +      for (i = 0; i < s->nb_streams; i++) {
> +        ebml_master tag_target;
> +        ebml_master tag;
> +
> +        mkv_write_tag_targets(s, MATROSKA_ID_TAGTARGETS_TRACKUID, i + 1, &tags, &tag_target);
> +
> +        tag = start_ebml_master(s->pb, MATROSKA_ID_SIMPLETAG, 0);
> +        put_ebml_string(s->pb, MATROSKA_ID_TAGNAME, "DURATION");
> +        mkv->stream_duration_offsets[i] = avio_tell(s->pb);
> +
> +        // Reserve space to write duration as a 20-byte string.
> +        // 2 (ebml id) + 1 (data size) + 20 (data)
> +        put_ebml_void(s->pb, 23);
> +        end_ebml_master(s->pb, tag);
> +        end_ebml_master(s->pb, tag_target);
> +      }
> +    }
> +
>      for (i = 0; i < s->nb_chapters; i++) {
>          AVChapter *ch = s->chapters[i];
>  
> @@ -1801,6 +1841,9 @@ static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt, int add_
>      }
>  
>      mkv->duration = FFMAX(mkv->duration, ts + duration);
> +    mkv->stream_durations[pkt->stream_index] =
> +        FFMAX(mkv->stream_durations[pkt->stream_index], ts + duration);
> +

this is called for webm too though

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Old school: Use the lowest level language in which you can solve the problem
            conveniently.
New school: Use the highest level language in which the latest supercomputer
            can solve the problem without the user falling asleep waiting.
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