[FFmpeg-user] I found the bugs

[Mark Filipak]

Let me bring everyone up to date.
ffmpeg -i ... -f framecrc
ffmpeg -i ... -vf showinfo
ffmpeg -i ... -show_frames
All show differing DTS and PTS timestamps. showinfo & show_frames have 2 second gaps.
The question is: Which one shows the actual timestamps?

The MPV player pauses during that 2 seconds -- MPV gets timestamps from FFmpeg.
The VLC & PowerDVD players _do_not_ pause.
The question is: Why does MPV have problems with a video that VLC & PowerDVD play?

framecrc matches the actual timestamps. I read the actual timestamps in the actual PES headers in 
the actual packets. So, I conclude that framecrc is correct and that showinfo & show_frames are wrong.
The question is: Why are three different parts of FFmpeg getting three different timestamps?

Why is this important?
Every time you transcode, you're using timestamps from FFmpeg.
Every time you splice (trim and join) you're using timestamps from FFmpeg.
Every time you get discontinuous DTSes, FFmpeg timestamps determine it.

For your tasks, is FFmpeg getting the correct timestamps or the bogus timestamps?

Believe me, I now know how to do perfect splices. It's hard, time consuming, and nerve wracking, but 
I know how to do it. Do you? Wouldn't it be nice if FFmpeg did them consistently, and consistently 
correctly? Then we all could all use '-ss' '-to' and a thousand other things with confidence.

I submitted the bug here: https://trac.ffmpeg.org/ticket/11055

In comment 7, I wrote:
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"I can't parse M2TSes. So, I don't know if there's something else that's tripping up FFmpeg.
For example, there may be something is M2TS having to do with sequence header that's not in
VOBs."
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In comment 26, I wrote:
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I guess there is 'something else'.
I discovered this: "co located POCs unavailable" while transcoding (AVC->HEVC) and remuxing
(M2TS->MP4). POCs are particular to H.264.

Of course, it has no bearing on why framecrc, showinfo, and show_frames differ.

I read about POCs in H.264. I think there might be an effect on DTSes & PTSes.
Can you help me out with this?
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Can all who read this message help me out, and thereby help yourself? Ask and I'll tell you how.

--Mark.