From: Marth64 <mart...@proxyid.net>
Sent: Thursday, January 30, 2025 5:44 AM
To: Soft Works <softwo...@hotmail.com>
Cc: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>;
Kieran Kunhya <kieran...@googlemail.com>
Subject: Re: [FFmpeg-devel] [PATCH v2 00/11] fix broken CC detection and
ffprobe fields (cover letter)
> > For what it's worth, I have seen this and it can definitely happen.
> Hi, I have seen it too, especially with SCTE-20 samples. Thanks
Which kind of recurrence pattern are you talking about?
I don't think this is conforming to spec. I've been contacted by somebody who
was too afraid to post on this ML. He said that the one source from which
"sparse" CC data is coming from is a library named libcaption which produces
off-spec CC data.
As mentioned before: off-spec CC data or a CC stream appearing due to changes
in broadcast can still be detected via analyze_frames. That's not much
different to frame size changes, which can also happen at any later point in
time. But what's relevant is the frame size at the beginning and CC data in the
same way. For spec-conforming streams, this method is very reliable. Most
importantly: it doesn't waste precious time by processing the initial frames
twice.
Even if it was just 98% reliable, those 2% could not serve as justification for
why probing of the 98% takes twice or thrice the time.
sw
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