VHS capture thru DV cam and FireWire - resulted framerate 24.992 ???

[dumb13]

Folks,

Most recently I have run into a strange problem: I am archiving my VHS tapes to DVD/VCD using my Sony mini-DV camcorder as an A/D converter between the VCR and the PC, and using Adobe Premiere 6.0 for capturing.

The latest captured .avi turns to be having a framerate of 24.992 instead of 25.000 fps, which causes the video and audio totally out of sync after encoding (I use CCE for video, and TMPGEnc for the audio stream). The encoded MPEG video has the same number of frames as the original .avi, but the correct 25.000 fps framerate - thus the length of the compressed video is shorter, while the compressed audio is exactly as long as the original. So on the 125 min. material I experience an about 3 sec. audio delay by the end of the video.


My questions:

- anybody experienced similar? How comes that the DV output is not exactly 25.000 fps??? (never happened before, nor when transferring DV material to PC)

- how can I fix this? My first idea was to modify the framerate info in the AVI header. The only tool I knew was "Avifrate" (v1p10), but it did not touch the 26GB file for some reason, while worked fine on smaller (couple of hundred MBs) test pieces.

- or is the only solution to convert the audio file (i.e., in CoolEdit) to the same length as the MPEG video? (takes ages)


Thanks for any ideas
Regards
dumb

[aklendathu]

I've had a similar problem, also while capturing VHS through the A/D converter of a Digital8 Sony Camcorder. I noticed the audio out going out of sync for long captures (more than 10-15 min) but didn't check the framerate (24.99 in Windows shows up as 25 anyway).
Funny thing is, if you record the VHS video on mini-DV and then capture the the mini-DV play back through the FireWire port, you'll probably be OK.

Could this be a some sort of time synchronization problem in the Sony A/D conversion chip ?

[dumb13]

the framerate (24.99 in Windows shows up as 25 anyway) Unfortunatelly, in Windows 2000 (file/properties/summary) it shows 24.992, as well as all other programs I tried (ULVS7, AP6, WMP, etc.)

if you record the VHS video on mini-DV and then capture the the mini-DV play back through the FireWire port, you'll probably be OK. I also had the idea, it would be really poor from Sony, if it worked the way around, making the recording function practically useless!



Still, there are some problems, really pain in the neck:

- the DV casette can hold only 1 hr video, so a full movie would need at least two (or - as in my particular case, it is 125 min. - three) casettes, and also two/three user interaction during dubbing

- the double procedure (VHS to DV, DV to PC) requires double dubbing time, plus

- it is pretty hard to hit the cut point at the beginning of the new casette, exactly as cut at the end of the previous

- or, one may edit the two/three parts to cut off redundant parts, and merge the whole stuff into one file

- in both cases, it takes enourmous user time, and almost sure the audio will "hickup" at the cut points


But some more information to the original case:

- I have found a new AVIFrate version here (freeware) (http://www.am-soft.ru/avifrate.html) which actually could modify the AVI header to show exactly the 25.000 fps - nevertheless, it did not help, even more, the original avi file get out of sync, though setting back to 24.992 it was again OK.

- I made some tests, and even on shorter materials the resulted DV/AVI files tend to show 25.000 +/- .00x framerate instead of the exact 25.000, what is REALLY WEIRD!
I am curious, if it is really the SONY A/D chip, or might be some environmental problem in Windows?

- finally, I saved the audio from the avi to wav in VirtualDub, than cut and squeezed in CoolEdit. Scenarist converted the wav to ac3 without any problem, so my MPEG2 video and the new AC3 audio were in perfect sync on the final DVD - but gee, do I need to do it every time???

Hope someone lits the spark in the dark :)

Regards dumb

[aklendathu]

Originally posted by dumb13
Unfortunatelly, in Windows 2000 (file/properties/summary) it shows 24.992, as well as all other programs I tried (ULVS7, AP6, WMP, etc.)

I also had the idea, it would be really poor from Sony, if it worked the way around, making the recording function practically useless!

...

- finally, I saved the audio from the avi to wav in VirtualDub, than cut and squeezed in CoolEdit. Scenarist converted the wav to ac3 without any problem, so my MPEG2 video and the new AC3 audio were in perfect sync on the final DVD - but gee, do I need to do it every time???

Hope someone lits the spark in the dark :)

Regards dumb

Glad you worked it out.
Your solution may be useful for me as well.

As for the Sony A/D, is it a bug or an undocumented feature ... ;)

[Andykard]

I also have a Sony digital 8 camcorder and I use it to transfer some of my VHS and laserdiscs to DVD very succesfully. I use the method of copying to DV tape 1st instead of using the camera as the converter (I got weird motion artifacts doing it this way). The procedure is actually very easy. Just make sure you duplicate the end of the movie on tape 1 onto the beginning of tape 2 and the same for tape 2 and 3. Then you can use Premiere to skip through the frames at the end and beginning frame by frame to set the in and out points, then place the video on the time line. You can then export audio only and then video only (CCE plugin for Premiere comes in very useful here).
Then use your Scenarist decoder to convert the wavefile to ac3. This has given me perfectly synched audio and video of very good quality for DVD.

[Kika]

Sounds like the Converter is producing dropped Frames because of Sync-Problems with the VHS-Tape.

[dumb13]

Originally posted by Kika
Sounds like the Converter is producing dropped Frames because of Sync-Problems with the VHS-Tape.

kika,

Thanks for the post.
I guess you mean the sync of the video signal on the tape? Than how would it result in dropped frames and how can we avoid it - please let us know if you have some ideas.

Thanks
dumb

[Kika]

If realy a bad Sync is the problem, the only solution i know is a VCR with a TBC or an external TBC (Time base Correction).
An other way is to use a Capture-Card with a BT8x8-Chip. You can set vertikal resolution to less than 576/480 lines, (572 - 574 / 476 - 478). This solves the problem in most cases.

[aklendathu]

Kika, dumb13,

A more subtle problem may be (uneducated guess) caused by the Firewire PCI card. For example, Pinnacle sell DV capture cards which are more expensive than general retail ones. Up to now, I thought it was dumb of them (unless you get a HW/SW bundle) but maybe their card will have some additional circuits enabling A/V synchronicity in a situation like this ?...

[Kika]

@aklendathu

Firewire does only read digital streams, not more, not less. It has nothing special to do with Video, Firewire does not know anything about Video. ;)
If the Drivers are OK, all Cards will give you the same: a pure digital Stream.

[aklendathu]

Like I said, it was an uneducated guess ... :p