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?
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
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
--
Thanks,
Limin Wang
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
