[FFmpeg-devel] [PATCH v8 3/3] avdevice/decklink_dec: export timecode with s12m side data

[lance.lmwang at gmail.com]

On Mon, Jul 13, 2020 at 10:24:11AM -0400, Devin Heitmueller wrote:
> On Sun, Jul 12, 2020 at 6:16 AM <lance.lmwang at gmail.com> wrote:
> > I have add fate timecode testing for h264/hevc and haven't submit yet. But if
> > the frame rate > 30, I got one unexpected result after map SMPTE ST 12-1:2014
> > side data to HEVC timecode, the frame is 6bit only(2bit for tens of frame),
> > so to framerate > 30, it'll be divided by 2 with same timecode, but HEVC timecode
> > frame number can use 9bit and expect the frame > 30.
> 
> You should still divide it by 2, even though HEVC supports more bits
> for the frame number.  This is to be consistent with SMPTE 12-1
> timecode, and downstream muxers/outputs aren't going to know whether
> the upstream decoder was H.264 or HEVC.  On the encode side, you can
> multiple by 2 and use the field bit to determine whether to then add
> 1.  See SMPTE ST 12-1:2014 Sec 12.2.

Thanks for the comments, it's helpful, I'll try to fix it on encoder side.

> 
> There's an argument that we should add support for higher framerates
> to support SMPTE 12-3 (which supports fps > 60), but that should be a
> different side data field.  Right now the most important thing is that
> the behavior be consistent across decoders.
> 
> Devin
> 
> -- 
> Devin Heitmueller, Senior Software Engineer
> LTN Global Communications
> o: +1 (301) 363-1001
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-- 
Thanks,
Limin Wang