Re: [FFmpeg-devel] [PATCH v2 1/4] avcodec/eac3dec: add detection of Atmos spatial extension profile

[Hendrik Leppkes <h.leppkes@gmail.com>]

On Sat, Feb 18, 2023 at 2:15 AM Marth64 <marth64@proxyid.net> wrote:
>
> Signed-off-by: Marth64 <marth64@proxyid.net>
> ---
>  libavcodec/ac3dec.c     |  3 +++
>  libavcodec/ac3dec.h     |  1 +
>  libavcodec/avcodec.h    |  2 ++
>  libavcodec/codec_desc.c |  1 +
>  libavcodec/eac3dec.c    | 11 ++++++++++-
>  libavcodec/profiles.c   |  5 +++++
>  libavcodec/profiles.h   |  1 +
>  7 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
> index 0b120e6140..8cede139b8 100644
> --- a/libavcodec/ac3dec.c
> +++ b/libavcodec/ac3dec.c
> @@ -1714,6 +1714,9 @@ skip:
>      if (!err) {
>          avctx->sample_rate = s->sample_rate;
>          avctx->bit_rate    = s->bit_rate + s->prev_bit_rate;
> +
> +        if (s->eac3_extension_type_a == 1)
> +            avctx->profile = FF_PROFILE_EAC3_DDP_ATMOS;
>      }

This should probably be something like:
avctx->profile     = s->eac3_extension_type_a == 1 ?
FF_PROFILE_EAC3_DDP_ATMOS : FF_PROFILE_UNKNOWN;

This way the profile is properly reset when there is no extension (anymore).

>
>      if (!avctx->sample_rate) {
> diff --git a/libavcodec/ac3dec.h b/libavcodec/ac3dec.h
> index 138b462abb..0829f4b40d 100644
> --- a/libavcodec/ac3dec.h
> +++ b/libavcodec/ac3dec.h
> @@ -102,6 +102,7 @@ typedef struct AC3DecodeContext {
>      int eac3;                               ///< indicates if current frame is E-AC-3
>      int eac3_frame_dependent_found;         ///< bitstream has E-AC-3 dependent frame(s)
>      int eac3_subsbtreamid_found;            ///< bitstream has E-AC-3 additional substream(s)
> +    int eac3_extension_type_a;              ///< bitstream has E-AC-3 extension type A enabled frame(s)
>      int dolby_surround_mode;                ///< dolby surround mode                    (dsurmod)
>      int dolby_surround_ex_mode;             ///< dolby surround ex mode                 (dsurexmod)
>      int dolby_headphone_mode;               ///< dolby headphone mode                   (dheadphonmod)
> diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> index 39881a1d2b..0e85dd50a4 100644
> --- a/libavcodec/avcodec.h
> +++ b/libavcodec/avcodec.h
> @@ -1591,6 +1591,8 @@ typedef struct AVCodecContext {
>  #define FF_PROFILE_DTS_HD_MA   60
>  #define FF_PROFILE_DTS_EXPRESS 70
>
> +#define FF_PROFILE_EAC3_DDP_ATMOS         30
> +
>  #define FF_PROFILE_MPEG2_422    0
>  #define FF_PROFILE_MPEG2_HIGH   1
>  #define FF_PROFILE_MPEG2_SS     2
> diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
> index 199f62df15..4098d4f5a5 100644
> --- a/libavcodec/codec_desc.c
> +++ b/libavcodec/codec_desc.c
> @@ -2931,6 +2931,7 @@ static const AVCodecDescriptor codec_descriptors[] = {
>          .name      = "eac3",
>          .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52B (AC-3, E-AC-3)"),
>          .props     = AV_CODEC_PROP_INTRA_ONLY | AV_CODEC_PROP_LOSSY,
> +        .profiles  = NULL_IF_CONFIG_SMALL(ff_eac3_profiles),
>      },
>      {
>          .id        = AV_CODEC_ID_SIPR,
> diff --git a/libavcodec/eac3dec.c b/libavcodec/eac3dec.c
> index deca51dd3d..5c71751a0c 100644
> --- a/libavcodec/eac3dec.c
> +++ b/libavcodec/eac3dec.c
> @@ -464,7 +464,16 @@ static int ff_eac3_parse_header(AC3DecodeContext *s)
>      if (get_bits1(gbc)) {
>          int addbsil = get_bits(gbc, 6);
>          for (i = 0; i < addbsil + 1; i++) {
> -            skip_bits(gbc, 8); // skip additional bit stream info
> +            if (i == 0) {
> +                /* In this 8 bit chunk, the LSB is equal to flag_ec3_extension_type_a
> +                   which can be used to detect Atmos presence */
> +                skip_bits(gbc, 7);
> +                if (get_bits1(gbc)) {
> +                    s->eac3_extension_type_a = 1;
> +                }
> +            } else {
> +                skip_bits(gbc, 8); // skip additional bit stream info
> +            }
>          }
>      }
>
> diff --git a/libavcodec/profiles.c b/libavcodec/profiles.c
> index 7af7fbeb13..343b08f363 100644
> --- a/libavcodec/profiles.c
> +++ b/libavcodec/profiles.c
> @@ -45,6 +45,11 @@ const AVProfile ff_dca_profiles[] = {
>      { FF_PROFILE_UNKNOWN },
>  };
>
> +const AVProfile ff_eac3_profiles[] = {
> +  { FF_PROFILE_EAC3_DDP_ATMOS, "Dolby Digital Plus + Dolby Atmos"},
> +  { FF_PROFILE_UNKNOWN },
> +};
> +
>  const AVProfile ff_dnxhd_profiles[] = {
>    { FF_PROFILE_DNXHD,      "DNXHD"},
>    { FF_PROFILE_DNXHR_LB,   "DNXHR LB"},
> diff --git a/libavcodec/profiles.h b/libavcodec/profiles.h
> index 41a19aa9ad..6ebedbd03f 100644
> --- a/libavcodec/profiles.h
> +++ b/libavcodec/profiles.h
> @@ -58,6 +58,7 @@
>
>  extern const AVProfile ff_aac_profiles[];
>  extern const AVProfile ff_dca_profiles[];
> +extern const AVProfile ff_eac3_profiles[];
>  extern const AVProfile ff_dnxhd_profiles[];
>  extern const AVProfile ff_h264_profiles[];
>  extern const AVProfile ff_hevc_profiles[];
> --
> 2.25.1
>
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