My compressed audio messed up my synch

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My compressed audio messed up my synch

Postby DriftRoot » Fri Oct 19, 2007 9:20 am

It took me awhile to realize this, but my AMV (see banner below) developed a synching problem after I compressed my audio. It's so slightly off-synch that a lot of people would probably not even notice (it took me over a month, and I made it) or else assume I was just being sloppy...except that I wasn't sloppy. I spent a long, long, LONG time getting things to synch perfectly, only to have my uncompressed audio ruin all that effort. :x

1. Why did this happen?

2. How can I make sure it doesn't happen again?

I'm annoyed enough to want to re-upload the AMV WITH uncompressed audio, that's had badly compressing the audio screwed up my synching!!! But I can't have this continue to happen with my other projects, which can't absorb a 25MB audio track.
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Postby Sereenie » Fri Oct 19, 2007 10:18 am

I think something similar is mentioned in this thread.

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Postby DriftRoot » Fri Oct 19, 2007 11:23 am

Yeesh that's a long thread. @_@ And it seems that poor individual, who no doubt just gave me a preview of the hell I'm about the willingly enter, hasn't resolved this problem.

So what, there's only two people experiencing synch issues with compressed audio (who care about synch issues) out of how many editors around here? That seems a little unlikely.
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Postby Sereenie » Fri Oct 19, 2007 12:03 pm

Rereading the thread, it seems that the problem is not unheard of, it's just that no one really noticed or cared...

This post is the one where Kero777 reports on what did work for him. Actually, page 3 of the thread seems to be the most useful one, screenshots and all.

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Postby DriftRoot » Fri Oct 19, 2007 2:22 pm

Sereenie wrote:Rereading the thread, it seems that the problem is not unheard of, it's just that no one really noticed or cared...


I don't know how the vast majority of people can fail to notice or care, it's not a minor problem, IMO - then again, if one's synch is off to begin with, being off a little more is hardly going to matter (heck, it might improve things). And when I say perfectly synched, I mean a specific frame is synched to a specific place in the audio, where being off by one or two frames means your synch is off...yes, that's how particular I am about synching, that's how carefully I synch my stuff, that's why I'm mad about this, because the way my AMV looks, it seems like I didn't care (or didn't do it right).

Sereenie wrote:Actually, page 3 of the thread seems to be the most useful one, screenshots and all.


And yeah, that post is nice, until you read the next one they made:

"Unfortunately, I was wrong about what I posted yesterday. Sad I was dumb and previewed a part that didn't really have as much "timing" to it as other. It's still... off..."

What I basically got out of that entire thread is that I should try something other than XviD next time and hope to god it comes out OK. I was going to do this anyways, but it still disappointing not know how correct this problem.
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Postby DriftRoot » Wed Oct 24, 2007 11:10 am

Let me state, for the record, I was editing with uncompressed audio. I didn't edit with a compressed MP3, then export a WAV from Premiere, then compress that WAVed MP3 into another MP3.
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Postby Kero777 » Wed Oct 31, 2007 3:01 pm

Unfortunately Sereenie, DriftRoot is right. I never was able to fix the problem no matter what I did. Even when I used MP4/MKV: timing was still off. I think it's partly because of the very, very tiny bit of silence that Lame mp3 adds at the beginning and end to ensure that none of the song is cut off during the compressing.

DriftRoot wrote:Let me state, for the record, I was editing with uncompressed audio. I didn't edit with a compressed MP3, then export a WAV from Premiere, then compress that WAVed MP3 into another MP3.


Same thing here. MP3's can crash editing programs, so I always use Uncompressed WAVs. I'm not sure if it would make a difference either way though.

If anyone finds out anything out about this problem, please help us two very frustrated people out. :P Thanks.
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Postby lynit » Wed Oct 31, 2007 5:26 pm

Did you add any leaders or something?
I had that problem. Just removed them, marked where to sync it up in Vegas (I moved the audio, and added some blank space), then added some silence in Audacity using the stuff I marked in Vegas...

sounds like a lot, but it's really simple.
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Postby DriftRoot » Thu Nov 01, 2007 11:17 am

`Eclipse wrote:Did you add any leaders or something?
I had that problem. Just removed them, marked where to sync it up in Vegas (I moved the audio, and added some blank space), then added some silence in Audacity using the stuff I marked in Vegas...

sounds like a lot, but it's really simple.


Here's the thing, I do have bumpers, but should that really make any difference given the way they're attached to my AMV? In both the uncompressed video and uncompressed audio stages, the whole entire AMV (including bumpers) is one video segment and synchs perfectly with the music. When the audio is compressed, that's when things go screwy. Does silence get compressed a little more or something, moving the actual music up a half frame or so? Your resolution sounds like an extreme measure...I mean, I can't imagine doing that to synch up tracks in MEPs. :shock:

I had a theory I shared with Kero: perhaps its something system-specific causing this synch problem. I'd like to see someone who's NEVER run into this kind of synch issue take the same audio and video files we're using and compress them the same way we are. If it works perfectly, then it's probably something beyond out control and we're going to be stuck uploading AMVs with uncompressed audio for the rest of our editing lives.

If it was my bumpers causing the problem (if I still had my original AMV project file, I would test this out personally, but I don't so I can't [don't ask]), then how the heck do I get all my audio and video tracks and whatnot into one AMV without this synch problem? It took me forever to get my bumpers to play nice and I thought I finally figured it out. :cry:
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Postby Krisqo » Thu Nov 01, 2007 12:13 pm

This may not be the best solution but I do it all the time...

Export you audio uncompressed from your editing program so it will have any gaps you placed at either the beginning or end for bumpers and whatnot. Then compress THAT file. Seems to work for me :?
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Postby Kero777 » Thu Nov 01, 2007 9:53 pm

DriftRoot wrote:I do have bumpers, but should that really make any difference given the way they're attached to my AMV?


I don't think that's the problem. It happens to me even without the leaders. :? It's just that little bit that won't seem to fix... about 1, possibly 2 frame(s).

Since I have a pretty big file, it seems like I have three options:

1) Compress the music and have it off-sync with the video.

2) Keep the PCM audio and compress the video so much on the second pass that the video doesn't look appealing.

3) Keep the PCM audio and high quality video, but be left with a file that's 110MB in size.

*Passes out on desk* :sweat:
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Postby DriftRoot » Mon Nov 05, 2007 8:00 am

Krisqo wrote:This may not be the best solution but I do it all the time...

Export you audio uncompressed from your editing program so it will have any gaps you placed at either the beginning or end for bumpers and whatnot. Then compress THAT file. Seems to work for me :?


That's basically what I did with my bumpers. I made the intro/outro bumpers in AE, then plopped them, along with a giant, uncompressed AVI of my AMV, into one Premiere project and exported THAT, then compressed that. This is why I said perhaps the silence was being compressed more, but from what Kero says, that has nothing to do with it.

And my synch isn't even off by a few frames until the end of the AMV; the problem starts to get noticeable 20 seconds in or so, when it's off by a fraction of a frame. By the time you get to two minutes, though, all those fractions definitely added up.

2) Keep the PCM audio and compress the video so much on the second pass that the video doesn't look appealing.


You can always put a disclaimer in the AMV info about this problem to make people aware that you didn't have any choice but to massively compress the video.
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Postby Scintilla » Mon Nov 05, 2007 9:54 am

DriftRoot wrote:And my synch isn't even off by a few frames until the end of the AMV; the problem starts to get noticeable 20 seconds in or so, when it's off by a fraction of a frame. By the time you get to two minutes, though, all those fractions definitely added up.

Wow. That sounds as bad as if it was due to not being careful about the difference between 23.976 and 24 frames per second.

What did you use to compress the audio? BeSweet, VirtualDubMod, or something else?
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Postby DriftRoot » Tue Nov 06, 2007 3:20 pm

Scintilla wrote:Wow. That sounds as bad as if it was due to not being careful about the difference between 23.976 and 24 frames per second.

What did you use to compress the audio? BeSweet, VirtualDubMod, or something else?


That is not the problem. I don't think it is, anyways...great, now I'm paranoid. I've seen that problem before and as far as I recall, it's more obvious than what was going on with my AMV.

I used BeSweet.

Now I'm really paranoid. Tonight I'll remove the audio track and reattach it deliberately with 23.976 and 24 compression to see what happens. I didn't bother testing this before because I found it hard to believe I made that kind of blunder (I make worse blunders, though, so why in the world I couldn't do something like this is beyond even me). I think it's kind of funny no one's brought up this possibility to Kero or I before. :)
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Postby DriftRoot » Sat Nov 10, 2007 6:14 pm

*scratches her head* Ok, this just gets more and more bizarre...

I definitely had 24 FPS compressed audio, not 23.976 compressed audio, attached to my 24 FPS AMV. So that wasn't the problem.

Bizarreness: scrupulously watching my out-of-synch version and my in-synch version side by side, I am now finding it very difficult to see any synch issues with the former. This is maddening, because I know there were a number of places where the synch was off enough to make me cringe. What's changed? I have no idea.

I'm beginning to think that - for some reason - computers are occasionally having a harder time with the MP3 audio than the WAV audio. I've never seen the original WAV file out of synch, for whatever that's worth. This is fairly relieving (seems apparent I didn't mess up the audio), but also very worrying (something else is messing up the audio).

I'm going to keep an eye on this and see if the synch devolves again. I won't continue to fuss about it publicly, though, unless I figure out what the hell is going on. :P

Kero - if you're keeping tabs on this, I suggest you also try viewing your AMV on someone else's computer. I have no idea how bad your synch issue is, but if it's not too horrendous, it might be worth a shot.
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