[FFmpeg-devel] [PATCH 2/2] flvenc: Fix sequence header update timestamps

Jan Ekström jeebjp at gmail.com
Sun May 13 12:25:39 EEST 2018


On Fri, May 11, 2018 at 4:40 AM, Alex Converse <alex.converse at gmail.com> wrote:
> From: Alex Converse <alexconv at twitch.tv>
>
> ---
>  libavformat/flvenc.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/libavformat/flvenc.c b/libavformat/flvenc.c
> index 9b7cdfe7db..7aa2dbf9a6 100644
> --- a/libavformat/flvenc.c
> +++ b/libavformat/flvenc.c
> @@ -485,7 +485,7 @@ static int unsupported_codec(AVFormatContext *s,
>      return AVERROR(ENOSYS);
>  }
>
> -static void flv_write_codec_header(AVFormatContext* s, AVCodecParameters* par) {
> +static void flv_write_codec_header(AVFormatContext* s, AVCodecParameters* par, unsigned ts) {
>      int64_t data_size;
>      AVIOContext *pb = s->pb;
>      FLVContext *flv = s->priv_data;
> @@ -497,8 +497,7 @@ static void flv_write_codec_header(AVFormatContext* s, AVCodecParameters* par) {
>                  par->codec_type == AVMEDIA_TYPE_VIDEO ?
>                          FLV_TAG_TYPE_VIDEO : FLV_TAG_TYPE_AUDIO);
>          avio_wb24(pb, 0); // size patched later
> -        avio_wb24(pb, 0); // ts
> -        avio_w8(pb, 0);   // ts ext
> +        put_timestamp(pb, ts);
>          avio_wb24(pb, 0); // streamid
>          pos = avio_tell(pb);
>          if (par->codec_id == AV_CODEC_ID_AAC) {
> @@ -761,7 +760,7 @@ static int flv_write_header(AVFormatContext *s)
>      }
>
>      for (i = 0; i < s->nb_streams; i++) {
> -        flv_write_codec_header(s, s->streams[i]->codecpar);
> +        flv_write_codec_header(s, s->streams[i]->codecpar, 0);
>      }
>
>      flv->datastart_offset = avio_tell(pb);
> @@ -905,7 +904,7 @@ static int flv_write_packet(AVFormatContext *s, AVPacket *pkt)
>              }
>              memcpy(par->extradata, side, side_size);
>              par->extradata_size = side_size;
> -            flv_write_codec_header(s, par);
> +            flv_write_codec_header(s, par, (unsigned)pkt->dts);
>          }
>      }
>

Yes, this will get rid of the possible warning by casting, but you're
still dealing with system specifically sized variables, so you might
be doing int64_t ->uint64_t or int64_t->uint32_t.

I have no idea why the aversion of just using the same type in
`flv_write_codec_header` as what the DTS is (int64_t)? And why are we
completely ignoring the fact that FLV has timestamp wrap-arounds? Or
does this update header not care about that?

Best regards,
Jan


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