**FIXED** Analog Audio not lining up w/video

careh wrote on 12/3/2005, 7:21 PM
I had posted here describing a problem I was having with audio going out of sync with video when capturing from a Hi-8 analog camcorder using S-Video input on a video capture card and the computer motherboard sound card.

This problem appeared to occur after I hooked up a DV camcorder to the computer using firewire. Thinking back I know I had also installed some DVD burning software around the same time - so who knows if that had an effect on the settings. Anyway - the end result was 'audio out of sync with video' - and no amount of fooling around with Screenblast Movie Studio settings was fixing it. And deadlines were looming.....

Recently I dug up some documentation I had and I seem to have solved the problem.

The fix (for me anyway) was to set my audio card settings as follows:
(Now, some of this stuff may not be necessary - but hey - in the end it works...)

Double clicking the 'speaker' icon in the system tray (on bottom right of screen) - all 'mute' boxes are set blank - except for 'Video' - which is checked.

SPDIF, MIDI, AUX, VIDEO, CDAUDIO and Microphone volume levels are set to the minimum.

Master Volume, Wave, Line-in are set 3 clicks above minimum.

I have a Nvidea Sound card (I believe it is built in to the motherboard) - and when I double click the NVMixer icon in the system tray I see the sliders as follows:

Main section
Master 3 clicks above minimum
Bass, Mid, Treble all in the middle of the slider position

Output section
Wave - 3 clicks up
Synth, CD, Aux, Mic, Spdif all at minimum
Line 3 clicks up

Input section
Line in set as input source
Digitize Input and Mic Boost boxes both unchecked

After resetting these settings - I re-input video and it worked right away - perfect sync. yay!!!



The following is my original post:

I think I hit a switch I was not supposed to in Screenblast as just recently when I capture from my camcorder the audio is out of sync. from the video.

It starts out in sync. but then around the 10 minute or so mark it starts to get out of sync. My guess is it is slightly out of sync. right from the beginning - but it is not apprent in short clips.

I notice the audio track is longer than the video track.

I can get around it by selecting 'ignore grouping' and then manually moving the audio track until they line up - but that is a real pain.

Any tips appreciated as I have a bunch of editing to do before Christmas.

Comments

Tim L wrote on 12/3/2005, 8:29 PM
ummm, this is just kind of a guess, (okay, its really a big, uneducated guess) but it might be that your video capture is dropping frames. When you capture, see if there's a little counter somewhere that shows the number of dropped frames.

I think, but don't really know for sure, that when you drop frames on capture (because the computer or hard drive or something can't keep up), that the audio might still be captured without loss.

So if you had a 10 minute long clip, and only dropped about one frame per minute, your video would end up 10 frames short, which is about a third of a second (NTSC). If the audio captured without loss, you'd be 1/3 second out of synch by then.

Also, it might be possible that you have a setting somewhere setting your project to 30 frames per second, rather than 29.97 frames per second?

Again, these are just big, fat guesses, and maybe I should just shut up now and let somebody who knows what they're talking about post a reply.

Tim L
careh wrote on 12/3/2005, 9:37 PM
Guesses are good. Keep 'em coming & I'll report back with my findings.

There are no dropped frames are being reported (I turned off my anti-virus checker as it was causing dropped frames earlier).

The frame rate is 29.970 on the Media Pool files.

Also - the problem just started recently - in the past I could capture long segments with out the lag - or - at least I never noticed the lag. That is why I think I may have clicked on a switch in Screenblast Movie Studio I was not supposed to touch.

I have tons of unfragmented disk space - I am using a 200GB disk for the captures & I clean it off between captures.
Tim L wrote on 12/4/2005, 6:52 AM
Yeah, after I posted last night -- about the dropped frames thing -- the more I thought about, the less likely it seemed.

On DV capture, the audio and video are all together -- it's essentially just a file transfer from the camcorder to the computer. I think I'd read about such a situation before -- audio and video getting out of synch -- but now I'm thinking that might have been an analog capture situation, where the video and audio captures are actually two separate (but simultaneous) things.

Sorry, I don't have any other suggestions.

Tim L
careh wrote on 12/4/2005, 7:22 AM
Maybe this is an excuse for me to buy a Digital-8 camcorder. I understand they use firewire to transfer the a/v stream to the computer.

Do you think that would likely clear up my current probelm with audio/video sync. issues?
Chienworks wrote on 12/4/2005, 8:52 AM
How are you capturing now? DV over firewire is probably the most reliable capture method.
careh wrote on 12/4/2005, 9:30 AM
I'm using a HI-8 analog camcorder hooked to the computer with S-Video to a video capture card and the audio to the motherboard sound card.
Chienworks wrote on 12/4/2005, 12:31 PM
Are you capturing to AVI or MPEG? A setup like that is notorious for losing sync on MPEG captures, in fact, it's almost impossible to get an MPEG capture in sync when using two different devices. It's also possible for AVI captures to drift out of sync as either device might drop a sample or two independantly of the other.
careh wrote on 12/4/2005, 8:16 PM
The screen capture clips are .AVI

careh wrote on 12/4/2005, 8:32 PM
It is getting worse - now the audio is going out within the first minute. Ack!!
careh wrote on 12/5/2005, 8:37 PM
I searched the web and came across other posts talking about out of sync audio when using computer sound cards and analog video capture cards. I ended up copying the analog video to a DV camcorder & then sent it to the computer via firewire. This takes twice as long to get it done (from analog camcorder to DV camcorder and then from DV camcorder to PC via firewire) - but at least it works ... and with no capital investment for a Digital-8 camcorder.

I'm still interested if anyone can identify how to get the analog capture card / PC sound card working correctly again. I'm sure I must have twiddled with some setting - possibly when I initially connected the DV camcorder to the PC and imported some video into Screenblast Movie maker - maybe the DV camera auto-tweaks some setting?

Tim L wrote on 12/6/2005, 5:26 AM
With the firewire capture of DV video, the sound and video are already combined into a single file during the capture. With a digital camcorder, the capture is essentially just a file transfer. No conversions are taking place, just sending 1's and 0's from the camcorder to the PC. The captured file on the PC should be an *exact* copy of the data on the tape. Audio and Video should never get out of synch.

You might be able to save some time by seeing if you can capture the DV-converted video *while* you are playing it from the analog camcorder into the DV camcorder. Some camcorders have a "pass through" feature that instantly provides the real-time digital video stream out of the camcorder (to the PC) of whatever is being put into the camcorder. The camcorder just acts like a real-time converter. You might even be able to do this without having a tape in the DV camcorder. Check the manuals or experiment.

Tim L
careh wrote on 12/7/2005, 7:37 PM
I tried that at first - but as soon as I plugged in the firewire - the PC seemed to 'take over' the camcorder.

I'm using a Sony DPC-900
Chienworks wrote on 12/8/2005, 3:59 AM
In VidCap, under Options / Preferences / General, uncheck Enable DV device control. Then the camcorder will run independantly.
careh wrote on 12/8/2005, 8:10 PM
I changed the setting & now I can 'pass through' video from the analog HI-8 camcorder to the DV camcorder and onto the computer.

Thanks for the tip.

Only thing is - I have to turn the analog camcorder to play and then set the DV camcorder going in 'record' mode before I connect the firewire to the computer. I'm guessing that is so the DV camcorder begins taking the signal from the analog camcorder instead of teh computer?

Chienworks wrote on 12/9/2005, 7:16 AM
Could be. My DV camera doesn't support that function at all so i've never played with it. Various cameras behave in different ways so it's hard to generalize. But hey ... if it works, then it works.
careh wrote on 12/29/2005, 11:07 AM
Fixed - bump - see my first post