[FFmpeg-devel] [PATCH] libavformat/hlsenc.c: Populate OTI using AAC profile in write_codec_attr.

[David Johansen]

On Fri, Dec 22, 2023 at 8:10 AM Romain Beauxis <toots at rastageeks.org> wrote:

> This patch populates the third entry for HLS codec attribute using the
> AAC profile.
>
> The HLS specifications[1] require this digit to be the Object Type ID as
> referred to in table 1.3 of ISO/IEC 14496-3:2009[2].
>
> The numerical constants in the code refer to these OTIs minus one, as
> documeted in commit 372597e[3], confirmed by comparing the values in the
> code with the values in the table mentioned above.
>
> Links:
> 1: https://datatracker.ietf.org/doc/html/rfc6381#section-3.3
> 2: https://csclub.uwaterloo.ca/~ehashman/ISO14496-3-2009.pdf
> 3:
> https://github.com/FFmpeg/FFmpeg/commit/372597e5381c097455a7b73849254d56083eb056
>
> ---
>  libavformat/hlsenc.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
> index 7049956dd7..2551bac6ae 100644
> --- a/libavformat/hlsenc.c
> +++ b/libavformat/hlsenc.c
> @@ -418,8 +418,10 @@ static void write_codec_attr(AVStream *st,
> VariantStream *vs)
>      } else if (st->codecpar->codec_id == AV_CODEC_ID_MP3) {
>          snprintf(attr, sizeof(attr), "mp4a.40.34");
>      } else if (st->codecpar->codec_id == AV_CODEC_ID_AAC) {
> -        /* TODO : For HE-AAC, HE-AACv2, the last digit needs to be set to
> 5 and 29 respectively */
> -        snprintf(attr, sizeof(attr), "mp4a.40.2");
> +        if (st->codecpar->profile != AV_PROFILE_UNKNOWN)
> +            snprintf(attr, sizeof(attr), "mp4a.40.%d",
> st->codecpar->profile+1);
> +        else
> +            goto fail;
>      } else if (st->codecpar->codec_id == AV_CODEC_ID_AC3) {
>          snprintf(attr, sizeof(attr), "ac-3");
>      } else if (st->codecpar->codec_id == AV_CODEC_ID_EAC3) {
> --
> 2.39.3 (Apple Git-145)
>

I love this change, but it appears that st->codecpar->profile is always
AV_PROFILE_UNKNOWN when using libfdk_aac as the encoder. Any indications
where I should look for fix that so this can be used with that encoder?

Thanks,
Dave