[FFmpeg-user] Keeping A/V sync during telecine

[Eric Wilde]

At 06:14 PM 12/30/2017 +0000, Phil Rhodes wrote:
>Ordinarily, one would assume that a file marked as being 29.97fps should 
>be played at 24000/1001fps.

I can give you all kinds of examples of video content that switches
frame rates on the fly, often back and forth.  Typically, one sees
the beginning segment (i.e. the titles) in one frame rate and then
the actual content switches to another.  At the end, the frame rate
switches back (i.e. the credits).

I even have a set of DVDs with NTSC content on them that were sold
in the UK.  They are marked as PAL.  The first few frames are PAL
and then the content switches to NTSC.  I'm guessing that nobody at
the DVD producer was crazy enough to attempt scan converting it.
I'm not sure how a European DVD player handles the switch but any of
the video players that I use (e.g. mplayer, vlc) handle it and all
of the frame rate changes just fine (not to mention the frame size
changes).  Plus, ffmpeg was sure able to process this content and
anything else that has frame rate changes -- with no loss of audio
sync.

Telecine, in my opinion, was just somebody's misguided attempt to
turn film into video, with a standard frame rate.  Maybe at the
time, it was necessary.  But, given that video players seem to be
perfectly capable of switching frame rates on the fly, a rather
pointless exercise.  Not to mention a complete pain for anyone who
is trying to "fix" such a video at this moment in time.

                                 Eric