[FFmpeg-devel] [PATCH] avformat/hlsenc: support CODECS Attribute in hevc EXT-X-STREAM-INF

[Guangxin Xu]

On Mon, Oct 12, 2020 at 9:57 PM Steven Liu <lq at chinaffmpeg.org> wrote:

>
>
> > 在 2020年10月12日，21:45，Guangxin Xu <oddstone at gmail.com> 写道：
> >
> >
> >
> > On Mon, Oct 12, 2020 at 5:18 PM Steven Liu <lq at chinaffmpeg.org> wrote:
> > fix ticket: 8904
> > parse the SPS from extradata and get profile_tier_level
> > write the profile_tier_level info into CODECS Attribute
> >
> > reference to :
> https://developer.apple.com/documentation/http_live_streaming/hls_authoring_specification_for_apple_devices/hls_authoring_specification_for_apple_devices_appendixes
> >
> > Signed-off-by: Steven Liu <lq at chinaffmpeg.org>
> > ---
> >  libavformat/hlsenc.c | 41 +++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 41 insertions(+)
> >
> > diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
> > index cb31d6aed7..574d9f81e9 100644
> > --- a/libavformat/hlsenc.c
> > +++ b/libavformat/hlsenc.c
> > @@ -337,6 +337,43 @@ static void write_codec_attr(AVStream *st,
> VariantStream *vs)
> >          } else {
> >              goto fail;
> >          }
> > +    } else if (st->codecpar->codec_id == AV_CODEC_ID_HEVC) {
> > +        uint8_t *data = st->codecpar->extradata;
> > +        int i = 0;
> > +        int profile = FF_PROFILE_UNKNOWN;
> > +        int level = FF_LEVEL_UNKNOWN;
> > +
> > +        if (st->codecpar->profile != FF_PROFILE_UNKNOWN)
> > +            profile = st->codecpar->profile;
> > +        if (st->codecpar->level != FF_LEVEL_UNKNOWN)
> > +            level = st->codecpar->level;
> > +
> > +        while (data && (data - st->codecpar->extradata) <
> st->codecpar->extradata_size) {
> > +            /* get HEVC SPS NAL and seek to profile_tier_level */
> > +            if (data && (data[0] | data[1] | data[2]) == 0 && data[3]
> == 1 && ((data[4] & 0x42) == 0x42)) {
> > Read beyond the boundary if data + 1 - st->codecpar->extradata  >=
> st->codecpar->extradata_size
> ok
> > Is it possible reuese ff_hevc_decode_extradata here?
> it is in libavcodec, i don’t think depend libavcodec in hlsenc is a good
> way, so parse sps here.
>
Then, we have a lot of hard work:
1. remove emulation prevent code.
2. get profile/level from vps too.
full details you can check at
https://github.com/FFmpeg/FFmpeg/blob/master/libavformat/hevc.c#L713
thanks



> >
> > +                int rbsp_byte_size;
> > +                data += 7;
> > +                /* process by reference General NAL unit syntax */
> > +                profile = *data & 0x1f;
> > +                rbsp_byte_size = st->codecpar->extradata_size - (data -
> st->codecpar->extradata);
> > +                for (i = 0; i < rbsp_byte_size; i++, data++) {
> > +                    if (data[0] == 0 && data[1] == 0 && data[2] == 3) {
> > +                        data += 2;
> > +                        i++;
> > +                    }
> > +                    /* skip 8 + 32 + 4 + 43 + 1 bit */
> > +                    if (i == 11)
> > +                        level = *data;
> > +                }
> > +                break;
> > +            }
> > +            data++;
> > +        }
> > +        if (st->codecpar->codec_tag == MKTAG('h','v','c','1') &&
> > +            profile != FF_PROFILE_UNKNOWN &&
> > +            level != FF_LEVEL_UNKNOWN) {
> > +            snprintf(attr, sizeof(attr), "%s.%d.4.L%d.B01",
> av_fourcc2str(st->codecpar->codec_tag), profile, level);
> > +        }
> >      } else if (st->codecpar->codec_id == AV_CODEC_ID_MP2) {
> >          snprintf(attr, sizeof(attr), "mp4a.40.33");
> >      } else if (st->codecpar->codec_id == AV_CODEC_ID_MP3) {
> > @@ -2247,6 +2284,10 @@ static int hls_write_header(AVFormatContext *s)
> >                  continue;
> >              }
> >              avpriv_set_pts_info(outer_st, inner_st->pts_wrap_bits,
> inner_st->time_base.num, inner_st->time_base.den);
> > +            if (outer_st->codecpar->codec_id == AV_CODEC_ID_HEVC &&
> > +                outer_st->codecpar->codec_tag !=
> MKTAG('h','v','c','1')) {
> > +                av_log(s, AV_LOG_WARNING, "Stream HEVC is not hvc1, you
> should use tag:v hvc1 to set it.\n");
> > +            }
> >              write_codec_attr(outer_st, vs);
> >
> >          }
> > --
> > 2.25.0
> >
> >
> >
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>
> Thanks
> Steven
>
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