On Sat, Jul 18, 2020 at 09:44:03AM +0200, Marton Balint wrote:
>
>
> On Sat, 18 Jul 2020, lance.lmw...@gmail.com wrote:
>
> > On Fri, Jul 17, 2020 at 07:13:28PM +0200, Marton Balint wrote:
> > >
> > >
> > > On Fri, 17 Jul 2020, lance.lmw...@gmail.com wrote:
> > >
> > > > From: Limin Wang <lance.lmw...@gmail.com>
> > > > > In SMPTE ST 12-1: 2014 Sec 12.2, we need to mark the frame flag
> > > if the frame rate > 30FPS to
> > > > avoid interoperability issues. It will be used by the encoder to
> > > > identify even or odd frames
> > > > and correctly calculate the frame number of the SEI TC.
> > >
> > > This feature looks like it belongs to av_timecode_get_smpte_from_framenum
> > > and not into decklink. Also checking previous timecode and guessing
> > > something is a hack, especially since you have the exact source timecode.
> > If I understand correctly, it's not hacky, for the framerate > 30, the
> > source timecode will be
> > frame pair(it's limited by 2bits limit of frame number ten digital. Below
> > is one exmaple for 50fps
> > if you tested with SDI with TC.
> > 00:00:00:24
> > 00:00:00:24
> > 00:00:00:25
> > 00:00:00:25
> > 00:00:00:00
> > 00:00:00:00
>
> Have you actually tested this with a real SDI signal containing timecode?
Yes, have tested with SDI playback by decklink UltraStudio 4K mini with TC
enabled.
>
> Thanks,
> Marton
>
> >
> > That's why I check the last TC to get the frame is even or odd.
> >
> > Why not use av_timecode_get_smpte_from_framenum(), for it's calculated by
> > the string TC by one time,
> > so it lacks the information whether it's odd or even frame.
> >
> > >
> > > Regards,
> > > Marton
> > >
> > > > > ---
> > > > libavdevice/decklink_common.h | 1 +
> > > > libavdevice/decklink_dec.cpp | 14 ++++++++++++++
> > > > 2 files changed, 15 insertions(+)
> > > > > diff --git a/libavdevice/decklink_common.h
> > > b/libavdevice/decklink_common.h
> > > > index bd68c7b..8ddc411 100644
> > > > --- a/libavdevice/decklink_common.h
> > > > +++ b/libavdevice/decklink_common.h
> > > > @@ -151,6 +151,7 @@ struct decklink_ctx {
> > > > int channels;
> > > > int audio_depth;
> > > > unsigned long tc_seen; // used with option wait_for_tc
> > > > + uint32_t last_tc;
> > > > };
> > > > > typedef enum { DIRECTION_IN, DIRECTION_OUT}
> > > decklink_direction_t;
> > > > diff --git a/libavdevice/decklink_dec.cpp b/libavdevice/decklink_dec.cpp
> > > > index dde68ff..a60c01b 100644
> > > > --- a/libavdevice/decklink_dec.cpp
> > > > +++ b/libavdevice/decklink_dec.cpp
> > > > @@ -884,12 +884,26 @@ HRESULT
> > > > decklink_input_callback::VideoInputFrameArrived(
> > > > int metadata_len;
> > > > uint8_t* packed_metadata;
> > > > AVTimecode tcr;
> > > > + AVRational rate = ctx->video_st->r_frame_rate;
> > > > > if (av_timecode_init_from_string(&tcr,
> > > ctx->video_st->r_frame_rate, tc, ctx) >= 0) {
> > > > uint32_t tc_data =
> > > > av_timecode_get_smpte_from_framenum(&tcr, 0);
> > > > int size = sizeof(uint32_t) * 4;
> > > > uint32_t *sd = (uint32_t
> > > > *)av_packet_new_side_data(&pkt, AV_PKT_DATA_S12M_TIMECODE, size);
> > > > > + /* set the field flag if frame rate
> > > > 30FPS */
> > > > + /* Refer to SMPTE ST 12-1:2014 Sec 12.2 */
> > > > + if (av_cmp_q(rate, (AVRational) {30, 1})
> > > > == 1) {
> > > > + /* Odd frame */
> > > > + if (ctx->last_tc == tc_data) {
> > > > + if (av_cmp_q(rate, (AVRational)
> > > > {50, 1}) == 0)
> > > > + tc_data |= (1 << 7);
> > > > + else
> > > > + tc_data |= (1 << 23);
> > > > + }
> > > > + }
> > > > + ctx->last_tc = tc_data;
> > > > +
> > > > if (sd) {
> > > > *sd = 1; // one TC
> > > > *(sd + 1) = tc_data; // TC
> > > > -- > 2.9.4
> > > > > _______________________________________________
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> >
> > --
> > Thanks,
> > Limin Wang
> > _______________________________________________
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--
Thanks,
Limin Wang
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