Need help with Virtual Dub setting

[lost123]

Hello all, I am new and very far outside of my knowledge here! Help and patience please.... So far I have read some FAQ's on video capture. My set up is a very simple older dazzle 100 usb fed off of a set top box via rca plugs. I am simply trying to record some shows off of tv for when I am not home, I guess a poor man's tivo if you will. I need some help synchronizing my audio and video. It seems my video will playout before my audio. I have tried so many combinations in vd that my head is spinning. Can anyone point me in the right direction?

Thanks in advance.

[mgh]

try the sync to audio under options

[lost123]

I do have it checked off.

[Alexstarfire]

Does it seem like the audio is off by a set amount? Like it plays a fraction of a second or so before/after they actually speak. Or does the audio get farther and farther out of snyc? OR does it go in an out of sync? I'm assuming it's not the later since you're recording from a TV source.

For the first one you just go under the audio menu and click on "interleaving." There is a section that says "Audio skew correction." You put in the time (in milliseconds) that the audio is off by. You'll have to play around and find this number through trial and error. If sound comes before the animation/action then use positive values, otherwise use negative values. Based one what you said you'd use negative values here.

If the audio progressively gets more out of sync then there are a few things you may have to try. The first one is to go to the video menu and click on "Frame Rate." In the first section there is an option to make audio/video durations match. I believe the one you, and the other guy, are using is the one under the "options" menu, but this is only when you preview the video file, not for the conversion. If that doesn't work then the audio could have been converted improperly when you recorded the show. I don't have any experience fixing a messed up audio file so if this is the case then you might need to get help from someone else.

I hope that helps.

[hech54]

I do have it checked off.

And I believe you will need to UNcheck that if you wish to correct the audio sync as Alexstarfire describes.

[lost123]

Ok, I have tried some variations, but I am still lost

In Audio settings, I have Interleaving enabled, with 500ms of time preloaded, and interleave every 1 frame
Audio skew set to 0

In Video settings, I have asked for the video and audio to be matched.

I have unchecked sync to audio.

What I have noticed in my test file, 40 seconds long is that after about 4-6 seconds, the video plays faster than the sound. But also as the sound tries to catch up? the pitch of the sound increases.

Any suggestions here? The interface is bewildering to me with all of its options - some before the capture screen and some are in the capture mode.....grrrr....

[jagabo]

What I have noticed in my test file, 40 seconds long is that after about 4-6 seconds, the video plays faster than the sound. But also as the sound tries to catch up? the pitch of the sound increases.

This indicates you are dropping frames while capturing. Use a less CPU intensive video codec (or less CPU intensive options within the codec) and no audio compression.

Some fast video encoders:

HuffYUV, very fast, not much compression, high quality
PicVideo MJPEG, very fast, variable compression and quality
Divx (fastest settings), very fast, variable compression and quality

[lost123]

Thanks for the reply, the problem is I am using the Divx for fast motion already. The side bar with info never shows the cpu over 16% could there be another reason?

[jagabo]

Thanks for the reply, the problem is I am using the Divx for fast motion already.

You mean the old Divx 3 fast motion codec? You should use a more recent Divx. Divx5 or newer. If I recall correctly the fastest preset is only available in Divx5+ if you've registered but the next fastest setting will probably be fast enough.

The problem isn't just a matter of CPU usage. There is also disk latency. Divx normally writes an index (a list of all keyframes) at the end of the file. When recording it doesn't know when you're going to stop so it doesn't know where the end of the file will eventually be. So it pre-extends the file a bit, writes the index at the end, and then goes back and fills in the file with frames until it reaches that index. It then stops encoding, extends the file some more, moves the index to the new end of the file, and returns to filling the file with more frames. Your report of a glitch 4 to 6 seconds into a recording is a hint that this file extension behavior is the cause of your problem. Newer versions of Divx seem to have less of a problem with this -- probably because they are multithreaded and faster.

Also, be sure you are capturing to a drive that's not your boot drive and not an external USB drive (the boot drive may be interrupted occasionally by Windows' background maintenance, and external USB drives are too slow.

You can completely avoid the pre-extension problem by using HuffYUV. Of course, your files will be much bigger. But you should test it with it to verify that you can capture without any problems. Then you can start worrying about how to fix your problem with Divx.

[lost123]

Well thought out! Thank you I will test right now with Huffy, I was using Divx 4 that "came" with virtual dub install. I have access (according to the list) to divx 6.9.2

[lost123]

video is jumpy and audio still lags behind video. I am using a non boot drive for my recording.

[gll99]

What kind of pc are you using? Cpu speed, ram, size and type of hdd etc..

Even my old P4 1.6 will capture 640x480 with the fastest setting using the divx 6.xx with mp3 audio. if there is a lag its rarely more than a constant +250 ms adjustment if needed at all.

edit:
btw) If you are attempting to correct the problems of a file which was already captured then the skew should not be zero as you state but it should contain either a positive or negative value in ms. ie 250 = 1/4 of a second. Read the note near the skew box.

Are you using virtualdub as the capture program? If you are using the capture function within Virtualdub and wish to correct the problem before it happens then other suggestion will be forthcoming.

[jagabo]

The next place to look is in VirtualDub's Audio/Video sync settings. Go to Capture -> Timing... Under "Resync Mode" try selecting "Do not resync...". See if that works any better.

Also try disabling audio playback while capturing: Audio -> Enable Audio Playback -- off. I've seen that cause problems at times. Audio is still recorded, it's just not played while recording.