> On Mar 2, 2025, at 15:47, Jack Lau via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>
> wrote:
>
> 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 <jacklau1...@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';
> int level = AV_LEVEL_UNKNOWN;
> + char constraints[5] = "0";
>
> 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' &&
> + 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
>
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Thanks for your reply!
I already submit new patch, there are some changes in new patch:
1. Avoid using loop traversal,
2. optimize constraint default value processing,
3. and simplify the reading method of profile_compatibility_flags
BTW, I think the constraints[8] = “” maybe better, it can be check if the first
bit is ‘\0’ so that maybe faster?
Regards
Jack
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