DV transfers of different lengths?

[illicit1]

Hi there -

I'm hoping someone can explain to me what's happening here. I've attached a video showing 2 different transfers of the same VHS tape from different players via firewire DV recorder. When I put the two .dv files into Final Cut Pro to compare the two I notice one is about 24 minutes longer. This is over the corse of a 6 hour tape.

In between the VHS player and Sony DV recorder is a Datavideo 1000. The video that runs shorter was transferred using S-Video from an AG-1960 and the other is composite cables from a Panasonic AG-VP320 (was new out of the box in 2023).

I've actually attached 2 videos, each with the audio only on one of the videos. The clip shows both videos start off the same but not for long..

FWIW: I'm grabbing the DV with ffmpeg-dl on a Mac:
ffmpeg-dl -f avfoundation -capture_raw_data true -i DV-VCR -c copy -map -0 -f rawvideo filename.dv

Thanks!

[latreche34]

Probably one has a lot of dropped frames and audio sync problems, the other one captured properly.

[illicit1]

Quote:

Originally Posted by latreche34

Probably one has a lot of dropped frames and audio sync problems, the other one captured properly.

Would this be something due to maybe high CPU usage on the capturing computer that would cause dropped frames or an issue prior to sending it over firewire?

[latreche34]

It could be any of the above or a combination of, I won't be able to guess.

[lordsmurf]

Are you attempting to capture to an external HDD/SSD?

[aramkolt]

Hmm. Something definitely screwy there. DV is usually pretty resilient to audio sync problems even without a TBC in my personal experience.

The two tests I'd do now are:

Recapture the same section of tape using composite with the AG1960 and see if the audio lines up with the previously captured AG-VP320 sample - you should also easily be able to tell which has lip syncing problems pretty easily.

Do the same test without the TBC1000 in the chain, again looking for lip sync issues towards the end of the file.

While command line DV capture I'm sure can work, it just adds extra variables that could be causing a problem, so I'd also do the above testing with iMovie which is free and does save the files in their native DV format - you just have to "show package contents" of the movie project to go and grab the .dv files at the end after saving and closing the project.

If you are saying before that there never were lip syncing issues on either file and one just plays faster, seems like something is being resampled to like a different frame rate (and audio rate) on one or the other.