Comments

Chienworks wrote on 5/14/2002, 1:40 PM
What hardware are you using to capture with? If you're doing analog captures, many of the cheaper capture cards/devices have sync problems. ATI in particular is very troublesome. I've been using a Sony DVMC-DA2 external analog A/V -> DV converter and capturing VHS tapes through firewire. Even 4 hour long captures come out in perfect sync beginning to end.
jrstueve wrote on 5/14/2002, 1:58 PM
Is it true that the sync problem is because of dropped frames?
Chienworks wrote on 5/14/2002, 2:05 PM
It can be, but not necessarily. When i was using a Hauppauge WinTV for capturing analog video, any time a frame was dropped, the previous frame was duplicated to fill in the space.
craigunderhill wrote on 5/14/2002, 2:13 PM
i capture through my sony tv120 digital8 cam.
SonyDennis wrote on 5/14/2002, 3:56 PM
Some other programs have had problems with DV footage that uses "unlocked" audio from certain brand cameras. It didn't really come to 48,000 samples per second, and caused audio drift because the NLE treated it like 48K. Vegas compensates for this, and keeps the audio in sync.
///d@
craigunderhill wrote on 5/14/2002, 4:15 PM
hmmmm....cool. i'll check it out in the demo and see how it does.

thanks.

HPV wrote on 5/14/2002, 10:23 PM
Some other programs have had problems with DV footage that uses "unlocked" audio from certain brand cameras
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Vegas has problems also. It's not a sync. thing, but to much or to little audio vs. video during capture. I get few samples less audio than video. Others say they get more audio than video. VidCap 2.5 and 3.0 both do this. If it's a problem with my Digital 8 camera, I would think it would happen all the time.
For those that want to check their system, just single click on a file in the Vegas explorer window and note the times for the video steam vs. the audio steam. And/or put the clip on the timeline, set the cursor to the end (Cntrl/Alt/Right arrow)and then horz. zoom in 100%. I've changed the internal settings to 48K from 44.1K with no effect. Both in Vegas and VidCap.

Craig H.
Caruso wrote on 5/15/2002, 3:53 AM
I'd like to comment with the fore-notice that said comment is not intended as a contradiction or putdown to any previous post/poster in this thread.

I'm just finishing the second of two two-hour programs, both shot using three cams running simultaneously. Only one of the three cams was digital, the other two were analog 8mm. All were captured through the digital 8mm cam.

The only sync problems I experienced were caused by obvious gaps in the recordings caused by the respective operators of their respective cam.

I experienced no other sync problems in either session. That's six hours times two of recording. I'm using VV30.

I have, indeed, experienced sync problems with vidcap 2.5, as well as with other mfrs software.

I wouldn't pretend to know what caused those problems, but, am happily (confidently) free of them for now.

Caruso
SonyDennis wrote on 5/15/2002, 7:58 AM
You're right that Vegas reports different stream lengths for audio and video, and that's true, because audio is measured in samples and video in frames, and an integral number of both, at 29.97 fps and 48,000 sps usually never equates to the exact same length. However, they should be within 33mS (one frame period) of each other. This would not be considered a sync drift.

If you're seeing more of a difference than that, please let us know the circumstances that led up to it. Thanks.

///d@
HPV wrote on 5/15/2002, 9:56 PM
and an integral number of both, at 29.97 fps and 48,000 sps usually never equates to the exact same length.
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Cool, thanks for the info. I guess a few samples missing between clips can't be heard? I can't hear it. Would setting the master stream to video or audio in the capture prefs help this little difference in stream length?
Also,see my new thread concerning rendering and interleave.

Craig H.
SonyDennis wrote on 5/17/2002, 12:06 AM
With DV, I don't think you can separate the audio or video to be the "master" sync reference, they are interleaved in the camera, and "glued" together from there. They are typically derived from the same time reference, so the can't drift.

I saw your post about interleave, and I'm not sure why it's changing the stream lengths, but I wouldn't worry about it too much. It's not making the streams out of sync, it's just extending one longer. Those 1501 samples are probably silence.

///d@
HPV wrote on 5/17/2002, 2:02 AM
Opps, I know see the master stream option is for analog capture. So on capture I get great sync., but some files end up with a few samples less audio. Trimming the tail cleans it up, no biggie.

>>I saw your post about interleave, and I'm not sure why it's changing the stream lengths, but I wouldn't worry about it too much. It's not making the streams out of sync, it's just extending one longer
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To stay on thread, I also get great sync. with final output via rendered files and VidCap playback. The factory settig of interleave will cause extra audio on rendered DV files. This can be a problem (black blip of one frame) with both rendered files on the timeline and maybe with VidCap 3.0 and multi files cueing ? Interleave every frame fixes this problem. So does making sure you snap to the video track, via zoom. Easy to trim away, but should need to and you can't trim in VidCap.
Wanted to know if there is any downside to the one frame setting.
And to Craig U. - don't buy anything but Vegas or Video Factory. The code is really solid stuff.

Craig H.