audio interleaving questions...preloading???

[angelleye]

I've had much trouble here in the past getting my a/v synch to work for me. I've used a bunch of different capture programs and I get different strange results from each. And also dependong on which video editing program I'm using.

I've been able to get my a/v synch to work in the past by using the interleaving options and delaying the audio by some time. After realizing that changing it to 500 would pretty much fix it, since under that option screen it shows "Preload 500 ms of audio before video starts". 500 is the default there. I've realized that if I just change that to 0 in the first place my a/v is in synch and I don't have to mess with delaying the audio.

I started to wonder when I realized that my original capture was perfectly in synch...but when I opened it in VDub or VDubMod it was immediately out of synch when previewing. Same happened with Pinnacle Studio, but not with Premiere or Ulead Video.

Why is the default option set to preload the 500 ms of audio when it's automatically screwing up my a/v synch? I've been changing it to 0 and I've been getting perfect encodes...I was just curious why that defaults to that if I'm doing something wrong by changing it. Right now it's all that works for me.

Any information would be great. Thanks!

Drew

[alexnoe]

If the preload values has any influence on sync, you should fire a phaser at the software you use (in this case, it seems to be the capture software or capture driver)

[angelleye]

Why is that? It seems kinda logical to me. If it's preloading 500 ms of audio before the video begins...then yeah, it's gonna be out of synch. Audio started first. And in all my reading about how to fix a/v synch I've seen many times that you should set the "delay audio track to 500 ms" to match the preload. Which...doesn't make much sense to me. Why preload it...then delay it the exact same time? What's weird...is this method doesn't seem to make it perfect for me. I'd have to set the delay to 400 or 600 usually. Whereas simply setting the preload to 0 seems to make it perfect in all my tests so far.

Any other info on this would be great. I'm using the most current capture driver provided by my card manufacturer. I'm using an ATI AIW 9700 Pro. I've also tried every peice of capture software I've seen listed on any boards or guides. I've tried VDub, VDubMod, Premiere, Pinnacle, ULead, AVI_IO, VDubVCR, VirtualVCR...and shot I can't even remember if there are more. AVI_IO does the best as far as dropping frames and a/v synch in the original, so that's what I've been using lately. Again, I'm satisfied with what I'm doing...final AVI looks great. I was just curious as to the whole preload thing.

[alexnoe]

No! The position in the file has nothing to do with the time it is played at! 'Preload' only has a cosmetic influence. If you set a 'delay', the muxer has to remove some data from the stream, or has to insert some silence data.

[angelleye]

cool...that explains the difference between them for me. thanks! still curious as to why the preload would be effecting things so much for me. And why it defaults to it.