[FFmpeg-devel] [PATCH 1/1] avformat/matroska: fully parse stsd atom in v_quicktime tracks

[Andreas Rheinhardt]

Stanislav Ionascu:
> Per matroska spec, v_quicktime contains the complete stsd atom, after
> the mandatory size + fourcc. By properly parsing the hvcc sub-atoms of
> the track, it becomes possible to demux/decode mp4/mov tracks stored as is
> in matroska containers.
> 
> Also dvh1 in stsd in matroska is more likely hevc codec than dv.
> 
> Signed-off-by: Stanislav Ionascu <stanislav.ionascu at gmail.com>
> ---
>  libavformat/matroskadec.c | 51 +++++++++++++++++++++++++++------------
>  1 file changed, 36 insertions(+), 15 deletions(-)
> 
> diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
> index 4e20f15792..88bc89c545 100644
> --- a/libavformat/matroskadec.c
> +++ b/libavformat/matroskadec.c
> @@ -2473,25 +2473,46 @@ static int matroska_parse_tracks(AVFormatContext *s)
>          } else if (!strcmp(track->codec_id, "V_QUICKTIME") &&
>                     (track->codec_priv.size >= 21)          &&
>                     (track->codec_priv.data)) {
> +            MOVStreamContext *msc;
> +            MOVContext *mc = NULL;
> +            AVIOContext *stsd_ctx = NULL;
> +            void *priv_data;
> +            int nb_streams;
>              int ret = get_qt_codec(track, &fourcc, &codec_id);
>              if (ret < 0)
>                  return ret;
> -            if (codec_id == AV_CODEC_ID_NONE && AV_RL32(track->codec_priv.data+4) == AV_RL32("SMI ")) {
> -                fourcc = MKTAG('S','V','Q','3');
> -                codec_id = ff_codec_get_id(ff_codec_movvideo_tags, fourcc);
> +            av_log(matroska->ctx, AV_LOG_TRACE,
> +                   "FourCC found %s.\n", av_fourcc2str(fourcc));
> +            priv_data = st->priv_data;
> +            nb_streams = s->nb_streams;
> +            mc = av_mallocz(sizeof(*mc));
> +            if (!mc)
> +                return AVERROR(ENOMEM);
> +            stsd_ctx = avio_alloc_context(track->codec_priv.data,
> +                                track->codec_priv.size,
> +                                0, NULL, NULL, NULL, NULL);
> +            if (!stsd_ctx)
> +                return AVERROR(ENOMEM);
I haven't looked at this patch deeply yet, but it seems to me that you
should rather use ffio_init_context like it is done in the code that
you intend to delete. That saves allocating and freeing stsd_ctx. You
can even reuse the AVIOContext b that already exists on the stack.
> +            mc->fc = s;
> +            st->priv_data = msc = av_mallocz(sizeof(MOVStreamContext));
> +            if (!msc) {
> +                av_free(mc);
> +                st->priv_data = priv_data;
> +                return AVERROR(ENOMEM);
>              }
> -            if (codec_id == AV_CODEC_ID_NONE)
> -                av_log(matroska->ctx, AV_LOG_ERROR,
> -                       "mov FourCC not found %s.\n", av_fourcc2str(fourcc));
> -            if (track->codec_priv.size >= 86) {
> -                bit_depth = AV_RB16(track->codec_priv.data + 82);
> -                ffio_init_context(&b, track->codec_priv.data,
> -                                  track->codec_priv.size,
> -                                  0, NULL, NULL, NULL, NULL);
> -                if (ff_get_qtpalette(codec_id, &b, track->palette)) {
> -                    bit_depth &= 0x1F;
> -                    track->has_palette = 1;
Why are you removing this code? What about tracks that ought to have a
palette?
> -                }
> +            /* ff_mov_read_stsd_entries updates stream s->nb_streams-1,
> +             * so set it temporarily to indicate which stream to update. */
> +            s->nb_streams = st->index + 1;
> +            ff_mov_read_stsd_entries(mc, stsd_ctx, 1);
> +            av_free(msc);
> +            av_free(mc);
> +            avio_context_free(&stsd_ctx);
> +            st->priv_data = priv_data;
> +            s->nb_streams = nb_streams;
> +
> +            // dvh1 in mkv is likely HEVC
> +            if (st->codecpar->codec_tag == MKTAG('d','v','h','1')) {
> +                codec_id = AV_CODEC_ID_HEVC;
>              }
>          } else if (codec_id == AV_CODEC_ID_PCM_S16BE) {
>              switch (track->audio.bitdepth) {
> 

Also, your patch should refer to the exact component that is about to
be changed: avformat/matroskadec.

- Andreas