> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of
> Kieran Kunhya via ffmpeg-devel
> Sent: Monday, January 27, 2025 10:40 AM
> To: FFmpeg development discussions and patches <ffmpeg-
> de...@ffmpeg.org>
> Cc: Kieran Kunhya <kieran...@googlemail.com>; Marth64
> <mart...@proxyid.net>
> Subject: Re: [FFmpeg-devel] [PATCH v2 00/11] fix broken CC detection
> and ffprobe fields (cover letter)
>
> >
> > While this is a very valid concern for some kinds of frame side
> data, it
> > does not apply to CC data. It's either in every frame or none. If a
> > provider generally broadcasts CC, then it's always present in every
> frame,
> > even during programs for which no CC is available - it's always
> there. Like
> > I mentioned at the top, we're using the properties field from the
> codec
> > (via codec_par) and there hasn’t been a single case reported where
> the CC
> > detection this way would have been incorrect.
> >
>
> This isn't true, CC data is sparse.
> I have no opinions about the rest of the text.
>
> Kieran
Hi Kieran,
Thanks for your reply.
In expectation of doubt, I had yesterday slightly modified ffprobe to count
frames with and without CC side data like this:
if (par->codec_type == AVMEDIA_TYPE_VIDEO) {
if (!is_sub && do_analyze_frames) {
int has_cc = 0;
for (int i = 0; i < frame->nb_side_data; i++) {
if (frame->side_data[i]->type == AV_FRAME_DATA_A53_CC) {
streams_with_closed_captions[pkt->stream_index]++;
has_cc = 1;
}
else if (frame->side_data[i]->type ==
AV_FRAME_DATA_FILM_GRAIN_PARAMS)
streams_with_film_grain[pkt->stream_index] = 1;
}
if (!has_cc) {
streams_without_closed_captions[pkt->stream_index]++;
}
}
}
Then I ran it on all kinds of mpegts recordings I had at hand, and that's the
result:
All video streams only, some were from the same file, others recorded in the
same way, hence the duplications.
+--------+----------------+-------------------+
| | Frames with CC | Frames without CC |
+--------+----------------+-------------------+
| stream | 786 | 0 |
+--------+----------------+-------------------+
| stream | 786 | 0 |
+--------+----------------+-------------------+
| stream | 786 | 0 |
+--------+----------------+-------------------+
| stream | 0 | 232 |
+--------+----------------+-------------------+
| stream | 0 | 238 |
+--------+----------------+-------------------+
| stream | 0 | 239 |
+--------+----------------+-------------------+
| stream | 0 | 237 |
+--------+----------------+-------------------+
| stream | 0 | 235 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 112 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 118 | 0 |
+--------+----------------+-------------------+
| stream | 58 | 0 |
+--------+----------------+-------------------+
| stream | 51 | 0 |
+--------+----------------+-------------------+
| stream | 42 | 0 |
+--------+----------------+-------------------+
| stream | 45 | 0 |
+--------+----------------+-------------------+
| stream | 42 | 0 |
+--------+----------------+-------------------+
| stream | 102 | 0 |
+--------+----------------+-------------------+
| stream | 45 | 0 |
+--------+----------------+-------------------+
| stream | 104 | 0 |
+--------+----------------+-------------------+
| stream | 42 | 0 |
+--------+----------------+-------------------+
| stream | 102 | 0 |
+--------+----------------+-------------------+
| stream | 44 | 0 |
+--------+----------------+-------------------+
| stream | 104 | 0 |
+--------+----------------+-------------------+
| stream | 42 | 0 |
+--------+----------------+-------------------+
| stream | 106 | 0 |
+--------+----------------+-------------------+
| stream | 44 | 0 |
+--------+----------------+-------------------+
| stream | 99 | 0 |
+--------+----------------+-------------------+
| stream | 41 | 0 |
+--------+----------------+-------------------+
| stream | 101 | 0 |
+--------+----------------+-------------------+
| stream | 45 | 0 |
+--------+----------------+-------------------+
| stream | 99 | 0 |
+--------+----------------+-------------------+
| stream | 32 | 0 |
+--------+----------------+-------------------+
| stream | 92 | 0 |
+--------+----------------+-------------------+
| stream | 40 | 0 |
+--------+----------------+-------------------+
| stream | 95 | 0 |
+--------+----------------+-------------------+
| stream | 37 | 0 |
+--------+----------------+-------------------+
| stream | 97 | 0 |
+--------+----------------+-------------------+
| stream | 34 | 0 |
+--------+----------------+-------------------+
| stream | 94 | 0 |
+--------+----------------+-------------------+
| stream | 37 | 0 |
+--------+----------------+-------------------+
| stream | 96 | 0 |
+--------+----------------+-------------------+
| stream | 34 | 0 |
+--------+----------------+-------------------+
| stream | 94 | 0 |
+--------+----------------+-------------------+
| stream | 35 | 0 |
+--------+----------------+-------------------+
| stream | 91 | 0 |
+--------+----------------+-------------------+
| stream | 43 | 0 |
+--------+----------------+-------------------+
| stream | 103 | 0 |
+--------+----------------+-------------------+
| stream | 40 | 0 |
+--------+----------------+-------------------+
| stream | 101 | 0 |
+--------+----------------+-------------------+
| stream | 43 | 0 |
+--------+----------------+-------------------+
| stream | 59 | 0 |
+--------+----------------+-------------------+
| stream | 0 | 5002 |
+--------+----------------+-------------------+
| stream | 0 | 725 |
+--------+----------------+-------------------+
| stream | 0 | 528 |
+--------+----------------+-------------------+
| stream | 0 | 7423 |
+--------+----------------+-------------------+
| stream | 0 | 3532 |
+--------+----------------+-------------------+
| stream | 0 | 9088 |
+--------+----------------+-------------------+
| stream | 0 | 105006 |
+--------+----------------+-------------------+
| stream | 0 | 104868 |
+--------+----------------+-------------------+
| stream | 0 | 50770 |
+--------+----------------+-------------------+
| stream | 74595 | 0 |
+--------+----------------+-------------------+
| stream | 0 | 90 |
+--------+----------------+-------------------+
| stream | 0 | 90 |
+--------+----------------+-------------------+
| stream | 0 | 95652 |
+--------+----------------+-------------------+
| stream | 0 | 8745 |
+--------+----------------+-------------------+
| stream | 0 | 2832 |
+--------+----------------+-------------------+
| stream | 0 | 7204 |
+--------+----------------+-------------------+
| stream | 0 | 7204 |
+--------+----------------+-------------------+
| stream | 0 | 7204 |
+--------+----------------+-------------------+
| stream | 0 | 7197 |
+--------+----------------+-------------------+
| stream | 0 | 7197 |
+--------+----------------+-------------------+
I can provide all (most) files privately. Happy to look into any examples if
you have.
Best
sw
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