[FFmpeg-devel] [PATCH v7 2/3] lavf/isom: support for demuxing and remuxing of MPEG-H 3D Audio in MP4

[James Almer]

On 12/12/2019 8:38 AM, Yuki Tsuchiya wrote:
> Implemented according to the specification at https://www.iso.org/standard/69561.html
> The 'mhm1' sample entry is registered with MP4RA, which is defined as MHAS encapsulated single stream MPEG-H 3D Audio.
> 'MHAS' stands for MPEG-H audio stream, which contains encoded audio data and corresponds metadata for decoding.
> This patch enables extracting the MHAS bitstream from MP4 and remuxing into MP4.
> 
> Signed-off-by: Yuki Tsuchiya <Yuki.Tsuchiya at sony.com>
> ---
>  libavcodec/avcodec.h    | 1 +
>  libavcodec/codec_desc.c | 7 +++++++
>  libavcodec/version.h    | 2 +-
>  libavformat/isom.c      | 1 +
>  libavformat/movenc.c    | 2 ++
>  5 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> index 735a3c2d76..119b32dc1f 100644
> --- a/libavcodec/avcodec.h
> +++ b/libavcodec/avcodec.h
> @@ -656,6 +656,7 @@ enum AVCodecID {
>      AV_CODEC_ID_ATRAC9,
>      AV_CODEC_ID_HCOM,
>      AV_CODEC_ID_ACELP_KELVIN,
> +    AV_CODEC_ID_MPEGH_3D_AUDIO,
>  
>      /* subtitle codecs */
>      AV_CODEC_ID_FIRST_SUBTITLE = 0x17000,          ///< A dummy ID pointing at the start of subtitle codecs.
> diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
> index 98b6348c59..0cae61bce0 100644
> --- a/libavcodec/codec_desc.c
> +++ b/libavcodec/codec_desc.c
> @@ -3016,6 +3016,13 @@ static const AVCodecDescriptor codec_descriptors[] = {
>          .long_name = NULL_IF_CONFIG_SMALL("Sipro ACELP.KELVIN"),
>          .props     = AV_CODEC_PROP_INTRA_ONLY | AV_CODEC_PROP_LOSSY,
>      },
> +    {
> +        .id        = AV_CODEC_ID_MPEGH_3D_AUDIO,
> +        .type      = AVMEDIA_TYPE_AUDIO,
> +        .name      = "mpegh_3d_audio",
> +        .long_name = NULL_IF_CONFIG_SMALL("MPEG-H 3D Audio"),
> +        .props     = AV_CODEC_PROP_LOSSY,
> +    },
>  
>      /* subtitle codecs */
>      {
> diff --git a/libavcodec/version.h b/libavcodec/version.h
> index 8b9c27378c..4c4027d709 100644
> --- a/libavcodec/version.h
> +++ b/libavcodec/version.h
> @@ -28,7 +28,7 @@
>  #include "libavutil/version.h"
>  
>  #define LIBAVCODEC_VERSION_MAJOR  58
> -#define LIBAVCODEC_VERSION_MINOR  64
> +#define LIBAVCODEC_VERSION_MINOR  65
>  #define LIBAVCODEC_VERSION_MICRO 101
>  
>  #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
> diff --git a/libavformat/isom.c b/libavformat/isom.c
> index edd0d81063..824e811177 100644
> --- a/libavformat/isom.c
> +++ b/libavformat/isom.c
> @@ -371,6 +371,7 @@ const AVCodecTag ff_codec_movaudio_tags[] = {
>      { AV_CODEC_ID_FLAC,            MKTAG('f', 'L', 'a', 'C') }, /* nonstandard */
>      { AV_CODEC_ID_TRUEHD,          MKTAG('m', 'l', 'p', 'a') }, /* mp4ra.org */
>      { AV_CODEC_ID_OPUS,            MKTAG('O', 'p', 'u', 's') }, /* mp4ra.org */
> +    { AV_CODEC_ID_MPEGH_3D_AUDIO,  MKTAG('m', 'h', 'm', '1') }, /* MPEG-H 3D Audio bitstream */
>      { AV_CODEC_ID_NONE, 0 },
>  };
>  
> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> index dd144ae20a..8456bfac6d 100644
> --- a/libavformat/movenc.c
> +++ b/libavformat/movenc.c
> @@ -2493,6 +2493,7 @@ static int mov_write_stbl_tag(AVFormatContext *s, AVIOContext *pb, MOVMuxContext
>      mov_write_stts_tag(pb, track);
>      if ((track->par->codec_type == AVMEDIA_TYPE_VIDEO ||
>           track->par->codec_id == AV_CODEC_ID_TRUEHD ||
> +         track->par->codec_id == AV_CODEC_ID_MPEGH_3D_AUDIO ||

This still depends on packets being flagged as key. One would hope they
were correctly flagged by a parser or demuxer, but there's always a risk
they were not, so if it's possible to do some basic parsing of the
bitstream to look for a sync code or similar, that would be ideal. See
the custom mov_parse_vc1_frame() and mov_parse_truehd_frame() functions
used for this purpose for an example.

If not possible, then this patch should be ok as is.

>           track->par->codec_tag == MKTAG('r','t','p',' ')) &&
>          track->has_keyframes && track->has_keyframes < track->entry)
>          mov_write_stss_tag(pb, track, MOV_SYNC_SAMPLE);
> @@ -6875,6 +6876,7 @@ const AVCodecTag codec_mp4_tags[] = {
>      { AV_CODEC_ID_DVD_SUBTITLE, MKTAG('m', 'p', '4', 's') },
>      { AV_CODEC_ID_MOV_TEXT    , MKTAG('t', 'x', '3', 'g') },
>      { AV_CODEC_ID_BIN_DATA    , MKTAG('g', 'p', 'm', 'd') },
> +    { AV_CODEC_ID_MPEGH_3D_AUDIO, MKTAG('m', 'h', 'm', '1') },
>      { AV_CODEC_ID_NONE        ,    0 },
>  };
>  
>