Re: [FFmpeg-devel] [PATCH] avformat/hlsenc: fix CODECS Attribute hard code in hevc EXT-X-STREAM-INF

[Steven Liu <lingjiujianke@gmail.com>]

Jack Lau via ffmpeg-devel <ffmpeg-devel@ffmpeg.org> 于2025年3月2日周日 15:47写道：
>
> fix ticket: 10786
> parse the SPS from extradata and get profile_compatibility, tier, constraints which was been hard code before.
>
> HEVC CODECS Attribute reference to: ISO/IEC14496-15
> Signed-off-by: Jack Lau <jacklau1222@qq.com>
> ---
>  libavformat/hlsenc.c | 37 ++++++++++++++++++++++++++++++++++---
>  1 file changed, 34 insertions(+), 3 deletions(-)
>
> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
> index 6148685f40..be7a78021a 100644
> --- a/libavformat/hlsenc.c
> +++ b/libavformat/hlsenc.c
> @@ -379,7 +379,10 @@ static void write_codec_attr(AVStream *st, VariantStream *vs)
>      } else if (st->codecpar->codec_id == AV_CODEC_ID_HEVC) {
>          uint8_t *data = st->codecpar->extradata;
>          int profile = AV_PROFILE_UNKNOWN;
> +        uint32_t profile_compatibility = AV_PROFILE_UNKNOWN;
> +        char tier = '0';
char tier = 0;
>          int level = AV_LEVEL_UNKNOWN;
> +        char constraints[5] = "0";
char constraints[8] = {0, }; Ensure alignment to 8.
>
>          if (st->codecpar->profile != AV_PROFILE_UNKNOWN)
>              profile = st->codecpar->profile;
> @@ -393,6 +396,8 @@ static void write_codec_attr(AVStream *st, VariantStream *vs)
>                  uint8_t *rbsp_buf;
>                  int remain_size = 0;
>                  int rbsp_size = 0;
> +                uint32_t profile_compatibility_flags = 0;
> +                uint8_t high_nibble = 0;
>                  /* skip start code + nalu header */
>                  data += 6;
>                  /* process by reference General NAL unit syntax */
> @@ -406,8 +411,31 @@ static void write_codec_attr(AVStream *st, VariantStream *vs)
>                  }
>                  /* skip sps_video_parameter_set_id   u(4),
>                   *      sps_max_sub_layers_minus1    u(3),
> -                 *  and sps_temporal_id_nesting_flag u(1) */
> +                 *  and sps_temporal_id_nesting_flag u(1)
> +                 *
> +                 * TIER represents the general_tier_flag, with 'L' indicating the flag is 0,
> +                 * and 'H' indicating the flag is 1
> +                 */
> +                tier = (int)(rbsp_buf[1] & 0x20) == 0 ? 'L' : 'H';
>                  profile = rbsp_buf[1] & 0x1f;



> +                /* PROFILE_COMPATIBILITY is general_profile_compatibility_flags, but in reverse bit order,
> +                 * in a hexadecimal representation (leading zeroes may be omitted).
> +                 */
> +                profile_compatibility_flags = (rbsp_buf[2] << 24) | (rbsp_buf[3] << 16) | (rbsp_buf[4] << 8) | rbsp_buf[5];
> +                /* revise these bits to get the profile compatibility value */
> +                for (int i = 0; i < 32; i++) {
> +                    profile_compatibility = (profile_compatibility << 1) | (profile_compatibility_flags & 1);
> +                    profile_compatibility_flags >>= 1;
> +                }
> +                /* skip 8 + 8 + 32
> +                 * CONSTRAINTS is a hexadecimal representation of the general_constraint_indicator_flags.
> +                 * each byte is separated by a '.', and trailing zero bytes may be omitted.
> +                 * drop the trailing zero bytes refer to ISO/IEC14496-15.
> +                 */
> +                high_nibble = rbsp_buf[7] >> 4;
> +                snprintf(constraints, sizeof(constraints),
> +                         high_nibble ? "%02x.%x" : "%02x",
> +                         rbsp_buf[6], high_nibble);



>                  /* skip 8 + 8 + 32 + 4 + 43 + 1 bit */
>                  level = rbsp_buf[12];
>                  av_freep(&rbsp_buf);
> @@ -417,8 +445,11 @@ static void write_codec_attr(AVStream *st, VariantStream *vs)
>          }
>          if (st->codecpar->codec_tag == MKTAG('h','v','c','1') &&
>              profile != AV_PROFILE_UNKNOWN &&
> -            level != AV_LEVEL_UNKNOWN) {
> -            snprintf(attr, sizeof(attr), "%s.%d.4.L%d.B01", av_fourcc2str(st->codecpar->codec_tag), profile, level);
> +            profile_compatibility != AV_PROFILE_UNKNOWN &&
> +            tier != '0' &&
tier should ok if it not 0
> +            level != AV_LEVEL_UNKNOWN &&
> +            strcmp(constraints, "0") != 0) {
> +            snprintf(attr, sizeof(attr), "%s.%d.%x.%c%d.%s", av_fourcc2str(st->codecpar->codec_tag), profile, profile_compatibility, tier, level, constraints);
>          } else
>              goto fail;
>      } else if (st->codecpar->codec_id == AV_CODEC_ID_MP2) {
> --
> 2.47.1
>
Thanks
Steven
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