Audio doesn't synch after rendering

L

Lynos

Well-known member
Hey guys

I finished editing my short film (shot in 24p on a Canon DSLR) and now I'm rendering it for Vimeo upload.

I've used the Sony AVC setting and made sure my frame rate is uniform all across the board and matches the source footage.

Despite all that, and despite the fact it synchs perfectly in the timeline, the audio after the rendering is out of synch with the video.
I tried rendering again with different methods such as AVI and Mainconcept and the result is the same.

I hope someone has an idea regarding this. I'm using Vegas Pro 10. Thank you.

Edit: I tried to post screen captures of my settings but was not able to (got lines of code instead of a picture).
 
Last edited:
Are you sure it's not a hardware issue, where the video playback isn't able to keep up with the audio?

Dave
 
Oh crap. This is embarrassing. I was so sure there was some exotic, elaborate problem in the settings, that I completely missed the simplest solution that was right under my nose!
Even though I tried different rendering methods, the footage always remained HD. And my computer is five years old (I had to edit with proxy files). So... it kind of makes sense. I guess I will have to upload it online and see if it works... because I cannot think of any other reason why it doesn't synch.

Thank you!
 
Okay, I rendered part of the video again as a test (Sony AVC, 1920X1080P) uploaded to YouTube and played it in SD, first 360p and then in 480p.
It's still out of synch.
So although the suggestion that it's not synching on my computer due to my hardware not being able to handle HD makes sense, it doesn't explain why it doesn't play well in standard definition.

Any suggestions are welcome...
 
At first it seemed the problem was in the timeline but now I'm not so sure. I corrected what I perceived to be the problem, and it played well in the timeline, but after rendering it, it again began drifting out of sync.

I'm still not sure what is the cause of this, timeline issues or render issues, but just for the sake of argument, what part of the rendering process can theoretically mess with the audio in this way?

Edit: I am using low resolution proxy files to edit. I cannot edit in HD or check audio sync with HD in real time. When I play it with the low res files in Vegas it seems fine. I then switch back to high res and then render out. I uploaded test clips to YouTube (so I can play it in SD and rule out hardware issues) and they almost immediatley begin drifting out of sync.
 
Last edited:
Yes.

But since they're HD I thought it was a hardware issue at first. I also tried it on other people's computers and the sync problem was still present.
 
Not that I can offer help, but I have seen this happen with clips that I was working on. Everything seems to be working properly while it is on the computer. Once I upload to youtube, there is a slight "off-synch" noticeable.
NO CLUE
 
I know there are many YouTube clips who are out of sync for some reason (and apparently the uplaoders don't really care because it just stays there), but I'm not sure if it's the same thing. Did you use Vegas to edit?
In my case, it plays wonky even before I upload it to YouTube.
 
Now that I think about it, there was an AVCHD synch issue in Vegas 10. Happened on the timeline of projects with a lot of clips -- I'd set the cursor to start playing at a certain point, and while the sound would play from there, the cursor would physically jump ahead several frames and play the video that many frames ahead of the sound.
 
Hmm... I'm not sure about that. For me the cursor stays put. Also, my project has about 30 clips. I don't know if that's considered a lot.
I also tried this with other codecs such as Mainconcept MP4 and it's even more choppy and out of sync.

By the way, one weird thing with the AVC codec is that sometimes it disappears from the render pull-down menu and I need to re-start Vegas in order to see it again. Don't know if that's gotta do with anything, though.
Across the internet it seems the AVC is the preferred codec to use, so... I dunno.

Anyway, I've dragged the rendered video file into my Vegas timeline to compare the two audio tracks and they're identical. So now I'm even more confused, because it means the audio did not corrupt during the render. So that means it's a playback issue.
I also rendered portions of my timeline in low-rez, especially some problematic sections that were out of sync before, and they played beautifully. I mean, they looked ugly as hell, but they synched!

I'll try and render again and see how it goes...

Thanks.
 
Lynos said:
Anyway, I've dragged the rendered video file into my Vegas timeline to compare the two audio tracks and they're identical. So now I'm even more confused, because it means the audio did not corrupt during the render. So that means it's a playback issue.
I also rendered portions of my timeline in low-rez, especially some problematic sections that were out of sync before, and they played beautifully. I mean, they looked ugly as hell, but they synched!
Click to expand...

Could be a frame rate issue? Are you sure that your rendering settings match your project settings?
 
Yes, rendering settings and project settings match.
And yes, proxy and HD files are identical, except for the resolution, of course. But can it be any other way? I mean, it's the same footage.

The only thing that is different is that the project audio was recorded with 48,000 khz sample rate, and my project/render settings were 44,100. But to my understanding, Vegas renders by project, not by file, so it shouldn't have mattered. And YouTube re-samples everything anyway.

Either way, I have now matched the sample rate all across the board just in case it had anything to do with it.
 
That sounds like a problem I have had with Sony AVC renders from AVCHD clips from my Sony HD Camcorder. Running the rendered file through tsMuxer fixes the sync problem for me. Might be worth a try in your case. Even if that works for you, it doesn't fix the root problem of Vegas creating out of sync renders, but is at least a workaround.
 
Last edited:
I don't know for sure what the problem was, but now it's in sync (after lots and lots of trial and error). I ended up using the AVC codec anyway. I switched in the last moment from 44,100 to 48,000 khz. Maybe that did the trick, I don't know.

Anyway, thanks everybody for your help and suggestions. That was a tough one.
 
Lynos said:
I switched in the last moment from 44,100 to 48,000 khz. Maybe that did the trick, I don't know.
Click to expand...

This is what I think was causing your problem. If you want to be sure, simply set it back to 44.1 kHz and see if the audio still matches.
 
It's not like it was out of sync and then when I switched to 48,000 everything miraculously got better. It got a little better even before. I was just doing it to be on the safe side. Maybe it improved things, maybe it didn't matter. I'll have to render it again with the old setting to test it and I'm not sure I wanna do it for the whole project.

The thing is, at Euginia's it says to use the sample rate in your project settings:

http://eugenia.queru.com/2007/11/09/exporting-with-vegas-for-vimeo-hd/

But Vimeo says you should use 44,100 khz:

https://vimeo.com/help/compression

If using 44,100 khz on a 48,000 khz project would've thrown it out of sync, then it wouldn't be recommended in any case, would it?
 
You must log in or register to reply here.
Back
Top