[FFmpeg-devel] [PATCH] libavformat/mov.c: Add parsing for DDTS atom for DTS audio

[Yusuke Nakamura]

2015-09-30 6:44 GMT+09:00 Shawn Singh <shawnsingh at google.com>:

> The DDTS atom is defined in ETSI TS 102 114, v1.4.1, Annex E.
> This is useful for DTS-HD formats, some of which cannot be
> decoded by dcadec.c or libdcadec.
>

How useful?
DTS audio has scalability, and 'ddts' box indicates only one of properties
of the stream.


>
> Signed-off-by: Shawn Singh <shawnsingh at google.com>
> ---
>  libavformat/mov.c | 56
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 56 insertions(+)
>
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index c57aaeb..da170a6 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -744,6 +744,61 @@ static int mov_read_dec3(MOVContext *c, AVIOContext
> *pb, MOVAtom atom)
>      return 0;
>  }
>
> +static int mov_read_ddts(MOVContext *c, AVIOContext *pb, MOVAtom atom)
> +{
> +    const uint32_t ddts_size = 20;
> +    AVStream *st = NULL;
> +    uint8_t *buf = NULL;
> +    uint32_t frame_duration_code = 0;
> +    uint32_t channel_layout_code = 0;
> +    GetBitContext gb;
> +
> +    buf = av_malloc(ddts_size + FF_INPUT_BUFFER_PADDING_SIZE);
> +    if (!buf) {
> +        return AVERROR(ENOMEM);
> +    }
> +    if (avio_read(pb, buf, ddts_size) < ddts_size) {
> +        av_free(buf);
> +        return AVERROR_INVALIDDATA;
> +    }
> +
> +    init_get_bits(&gb, buf, 8*ddts_size);
> +
> +    if (c->fc->nb_streams < 1) {
> +        return 0;
> +    }
> +    st = c->fc->streams[c->fc->nb_streams-1];
> +
> +    st->codec->sample_rate = get_bits_long(&gb, 32);
> +    skip_bits_long(&gb, 32); /* max bitrate */
> +    st->codec->bit_rate = get_bits_long(&gb, 32);
> +    st->codec->bits_per_coded_sample = get_bits(&gb, 8);
>

This field is set to 0 as a reserved field if the file is compatible with
Ultra Violet's Common File Format (CFF).
I prefer that the reference about this is here.


> +    frame_duration_code = get_bits(&gb, 2);
> +    skip_bits(&gb, 30); /* various fields */
> +    channel_layout_code = get_bits(&gb, 16);
> +
> +    st->codec->frame_size =
> +            (frame_duration_code == 0) ? 512 :
> +            (frame_duration_code == 1) ? 1024 :
> +            (frame_duration_code == 2) ? 2048 :
> +            (frame_duration_code == 3) ? 4096 : 0;
>

Wrong if LBRDurationMod is set to 1.


> +
> +    if (channel_layout_code > 0xff) {
> +        av_log(c->fc, AV_LOG_WARNING, "Unsupported DTS audio channel
> layout");
> +    }
> +    st->codec->channel_layout =
> +            ((channel_layout_code & 0x1) ? AV_CH_FRONT_CENTER : 0) |
> +            ((channel_layout_code & 0x2) ? AV_CH_FRONT_LEFT : 0) |
> +            ((channel_layout_code & 0x2) ? AV_CH_FRONT_RIGHT : 0) |
> +            ((channel_layout_code & 0x4) ? AV_CH_SIDE_LEFT : 0) |
> +            ((channel_layout_code & 0x4) ? AV_CH_SIDE_RIGHT : 0) |
> +            ((channel_layout_code & 0x8) ? AV_CH_LOW_FREQUENCY : 0);
> +
> +    st->codec->channels =
> av_get_channel_layout_nb_channels(st->codec->channel_layout);
> +
> +    return 0;
> +}
> +
>  static int mov_read_chan(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>  {
>      AVStream *st;
> @@ -3824,6 +3879,7 @@ static const MOVParseTableEntry
> mov_default_parse_table[] = {
>  { MKTAG('e','s','d','s'), mov_read_esds },
>  { MKTAG('d','a','c','3'), mov_read_dac3 }, /* AC-3 info */
>  { MKTAG('d','e','c','3'), mov_read_dec3 }, /* EAC-3 info */
> +{ MKTAG('d','d','t','s'), mov_read_ddts }, /* DTS audio descriptor */
>  { MKTAG('w','i','d','e'), mov_read_wide }, /* place holder */
>  { MKTAG('w','f','e','x'), mov_read_wfex },
>  { MKTAG('c','m','o','v'), mov_read_cmov },
> --
> 2.6.0.rc2.230.g3dd15c0
>
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