UPDATED Audio video synch mysteries

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audio_pete
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UPDATED Audio video synch mysteries

Post by audio_pete » Sun Jun 17, 2018 8:27 pm

Turns out problem is trusting FFmpeg to create an AC3 file.

Redid noise reduction
Change speed
00:31:27 + 14 PAL frames to
00:30:10 + 7 PAL frames

export AIFF

much nicer synch audio w video

I am not sure what the point of export AC3 is
it sure wasted a ton of my time. : (


Audacity 2.0.3 10.10.5

Back to the same problem
taking a second stab.

BBC Richard III broadcast TV
video taped with VHS analog recorder
"dubbed" to DVD with a LG combo VHS /DVD digital recorder
and. of course, audio and video are out of sync.
(last time it was Playboy of the Western World,
solution then was I found it streamed on Broadway HD for $$)

I just tried Audacity Tempo -4.96% change
no help
I tried Tempo seconds of audio to seconds of video
no help.
I think I even tried Tempo with +4.096%
i think.

Maybe It would help if I understood where the problem lies.
but I don't.

I guess its PAL to NTSC but how and why is a mystery
or at least not able to re synch them.

Added step, the LG player adds motor noise to audio
which I remove with Audacity before trying synch.

any suggestions?

Last steps using Wondershare Filmora to split von
detach audo
and replace audio.
Its displays are in PAL but that should not be a problem.
Other efforts not involving any PAL connection work just fine.
Last edited by audio_pete on Mon Jun 25, 2018 9:05 pm, edited 1 time in total.

kozikowski
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Re: Audio video synch mysteries

Post by kozikowski » Sun Jun 17, 2018 9:03 pm

About a frame per minute? Pretty much everybody can see the sync errors about five minutes in?

That's roughly the error you get when you assume NTSC runs at 30 instead of its real oddball-wacky framerate.

If that's it, you should be able to apply a correction of 1000/1001 to either one and they should slide right in.

I can't tell you which is ahead because the conversions make my head hurt. If sync fails and gets worse, try the other direction.

You can't really make a video DVD from a VHS tape. Tape shudder, split, velocity and timing errors are terrific, so the video has to go through a stabilizer somewhere to turn it back into broadcast video. Where is the PAL > NTSC conversion?

Koz

audio_pete
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Re: Audio video synch mysteries

Post by audio_pete » Sun Jun 17, 2018 10:38 pm

Here is where I got my first dope

https://forum.videohelp.com/threads/309 ... tch-change

will try your slight change and let you know if this is the answer.

Don't know answer to conversion question.
Am sure the original Richard III was PAL.
"Understand" that PBS had to convert video to NTSC to broadcast in US
but they could somehow do the audio on the fly.
So I think I have NTSC video and PAL audio.
But if that were true should be easy to fix, no?

Audacity puzzle , if Tempo speeds up why doesn't the file shorten?

audio_pete
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Re: Audio video synch mysteries

Post by audio_pete » Sun Jun 17, 2018 11:49 pm

Tried 0.000999
and -0.000999
neither worked
did I get my number right?
1000 / 1001

I think the LG combo machine just digitizes what is on the screen
and gets audio from ???

Do you think I could avoid the synch problem
by recording the sound from the VHS separately?
Not exactly sure how to do it.

audio_pete
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Re: Audio video synch mysteries

Post by audio_pete » Mon Jun 18, 2018 2:45 pm

Following last failed procedure
I have located a bit of silence
broken by sound
on the Audacity audio file it is 0h 23m 19s 128ms
on the video in Filmora it is 0h 22m 19s 240ms

What should the Tempo value be?

Believe me I have tried.

steve
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Re: Audio video synch mysteries

Post by steve » Mon Jun 18, 2018 2:55 pm

Try the "Change Speed" effect
The "Current length" should show 0h 23m 19s 128ms
The "New Length" control needs to be set to the required length (0h 22m 19s 240ms)
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)

audio_pete
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Re: Audio video synch mysteries

Post by audio_pete » Mon Jun 18, 2018 3:54 pm

Thanks for the suggestion.

I think I tried this already
will try again.

That is not the end of the file
and if I remember correctly
it will chop off the file at 22 minutes
cutting the last 38 minutes.

I believe my first try was on whole file
but it did not synch audio w video.

kozikowski
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Re: Audio video synch mysteries

Post by kozikowski » Mon Jun 18, 2018 6:31 pm

Effect > Change Speed can be very plain.

Select the sound track. Effect > Change Speed. Type in the existing length. Type in how long you want it. > OK.

Export the repaired track and see how well it matches.
Screen Shot 2018-06-18 at 11.17.52.png
Screen Shot 2018-06-18 at 11.17.52.png (7.8 KiB) Viewed 171 times
The other two change tools, Pitch and Tempo, try to rip the track apart and put it back together without changing anything else. They can create their own damage.

Change speed reduced everything at the same time. Generally, if you have a track mismatch problem through sample rate errors or playback speed, this is the one most likely to be helpful.

Next time you respond, it's useful to describe what happened. "It didn't work" isn't the most useful. Instead say: "It's better, but not enough," or "it got worse." Give us something to work with.

Koz

audio_pete
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Re: Audio video synch mysteries

Post by audio_pete » Mon Jun 18, 2018 11:41 pm

Of course, my change speed does not have that option.
Is that a new feature.

so upgrade to 2.2.2
but unable to load find after load LAME library
grrrrrrr
sourceforge is down?
will try later
no progress

other attempts were not even close
but will focus on one spot in future endeavors
if I ever get library loaded

audio_pete
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Re: Audio video synch mysteries

Post by audio_pete » Tue Jun 19, 2018 1:28 am

must have loaded 5 libraries
before I "found" the right one

all set up with new Audacity Change speed
but enough fun for today

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