Re: [FFmpeg-devel] [PATCH] avcodec/mxfdec: Recognize AAC per SMPTE ST 381-4

[Marton Balint <cus@passwd.hu>]

On Thu, 27 Apr 2023, Ammon Riley wrote:

> This patch simply recognizes the AAC audio tracks during
> decode -- it does not add functionality to encode AAC in
> MXF.
>
> A sample file (st381-4-sample.mxf) has been uploaded to
> https://streams.videolan.org/upload/, and is also available
> at https://harmonicinc.box.com/v/st381-4-sample.  Audio
> and video are both licensed as CC0.
>

> From 9765ec18f65b8ae147660e0d71bfa80293e57f56 Mon Sep 17 00:00:00 2001
> From: Ammon Riley <ammon.riley@harmonicinc.com>
> Date: Wed, 26 Apr 2023 18:26:35 -0700
> Subject: [PATCH] avcodec/mxfdec: Recognize AAC per SMPTE ST 381-4
> 
> This patch simply recognizes the AAC audio track during
> decode -- it does not add functionality to encode AAC in
> MXF.
> 
> Signed-off-by: Ammon Riley <ammon.riley@gmail.com>
> ---
>  Changelog            | 1 +
>  libavformat/mxf.c    | 1 +
>  libavformat/mxfdec.c | 5 +++++
>  3 files changed, 7 insertions(+)
> 
> diff --git a/Changelog b/Changelog
> index a40f32c23f..e68ee0f2c9 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -3,6 +3,7 @@ releases are sorted from youngest to oldest.
>
>  version <next>:
>  - libaribcaption decoder
> +- recognize AAC in MXF (SMPTE ST 381-4)

I think such small change does not warrant a changelog entry.

>
>  version 6.0:
>  - Radiance HDR image support
> diff --git a/libavformat/mxf.c b/libavformat/mxf.c
> index 8ef928b8fc..deb6091003 100644
> --- a/libavformat/mxf.c
> +++ b/libavformat/mxf.c
> @@ -78,6 +78,7 @@ const MXFCodecUL ff_mxf_codec_uls[] = {
>      { { 0x06,0x0E,0x2B,0x34,0x04,0x01,0x01,0x01,0x04,0x02,0x02,0x02,0x03,0x02,0x01,0x00 }, 15,        AV_CODEC_ID_AC3 },
>      { { 0x06,0x0E,0x2B,0x34,0x04,0x01,0x01,0x01,0x04,0x02,0x02,0x02,0x03,0x02,0x05,0x00 }, 15,        AV_CODEC_ID_MP2 }, /* MP2 or MP3 */
>    //{ { 0x06,0x0E,0x2B,0x34,0x04,0x01,0x01,0x01,0x04,0x02,0x02,0x02,0x03,0x02,0x1C,0x00 }, 15,    AV_CODEC_ID_DOLBY_E }, /* Dolby-E */
> +    { { 0x06,0x0e,0x2b,0x34,0x04,0x01,0x01,0x0D,0x04,0x02,0x02,0x02,0x04,0x00,0x00,0x00 }, 13,        AV_CODEC_ID_AAC }, /* AAC SMPTE 381-4 */

If I read the SMPTE registry correctly, AAC is only ... 0x04 0x03, and ... 0x04 0x04.

>      { { 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 },  0,       AV_CODEC_ID_NONE },
>  };
> 
> diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
> index 8a7008b298..c5960ecf0c 100644
> --- a/libavformat/mxfdec.c
> +++ b/libavformat/mxfdec.c
> @@ -1628,6 +1628,9 @@ static const MXFCodecUL mxf_sound_essence_container_uls[] = {
>      { { 0x06,0x0e,0x2b,0x34,0x04,0x01,0x01,0x01,0x0d,0x01,0x03,0x01,0x02,0x01,0x01,0x01 }, 14, AV_CODEC_ID_PCM_S16LE, NULL, 13 }, /* D-10 Mapping 50Mbps PAL Extended Template */
>      { { 0x06,0x0e,0x2b,0x34,0x01,0x01,0x01,0xff,0x4b,0x46,0x41,0x41,0x00,0x0d,0x4d,0x4F }, 14, AV_CODEC_ID_PCM_S16LE }, /* 0001GL00.MXF.A1.mxf_opatom.mxf */
>      { { 0x06,0x0e,0x2b,0x34,0x04,0x01,0x01,0x03,0x04,0x02,0x02,0x02,0x03,0x03,0x01,0x00 }, 14,       AV_CODEC_ID_AAC }, /* MPEG-2 AAC ADTS (legacy) */
> +    { { 0x06,0x0e,0x2b,0x34,0x04,0x01,0x01,0x0d,0x0d,0x01,0x03,0x01,0x02,0x16,0x00,0x00 }, 14,       AV_CODEC_ID_AAC, "aac_adif_smpte_381_4", 14 }, /* AAC SMPTE 381-4 */
> +    { { 0x06,0x0e,0x2b,0x34,0x04,0x01,0x01,0x0d,0x0d,0x01,0x03,0x01,0x02,0x17,0x00,0x00 }, 14,       AV_CODEC_ID_AAC, "aac_adts_smpte_381_4", 14 }, /* AAC SMPTE 381-4 */
> +    { { 0x06,0x0e,0x2b,0x34,0x04,0x01,0x01,0x0d,0x0d,0x01,0x03,0x01,0x02,0x18,0x00,0x00 }, 14,       AV_CODEC_ID_AAC, "aac_latm_loas_smpte_381_4", 14 }, /* AAC SMPTE 381-4 */

description fields are only used for data, so you can simply use NULL for them for AAC.

>      { { 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 },  0,      AV_CODEC_ID_NONE },
>  };
> 
> @@ -3029,6 +3032,8 @@ static int mxf_parse_structural_metadata(MXFContext *mxf)
>                      st->codecpar->codec_id = AV_CODEC_ID_PCM_S32BE;
>              } else if (st->codecpar->codec_id == AV_CODEC_ID_MP2) {
>                  sti->need_parsing = AVSTREAM_PARSE_FULL;
> +            } else if (st->codecpar->codec_id == AV_CODEC_ID_AAC) {
> +                sti->need_parsing = AVSTREAM_PARSE_FULL;
>              }
>              st->codecpar->bits_per_coded_sample = av_get_bits_per_sample(st->codecpar->codec_id);
>
-- 
2.29.2

Regards,
Marton
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