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

[Devin Heitmueller]

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.

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

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Devin Heitmueller, Senior Software Engineer
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