Can you offset the audio from the video?

[Dr. Macenstein]

Is there any way to offset the audio when making an AVI?

The audio is ahead of the video in my finshed AVIs by about half a second or so. (this is when viewed on the player, not the computer.)
I have seen WinMEnc 0.61 has an extra tab, and you can enter "General -delay 0.7" to keep the audio from playing until a certain point)

Anyone know of a way to do this in ffmpegx?

[rumplestiltskin]

I use QTSync - http://www.qtsync.com/e/about.php

...but I'm not positive about all the formats with which it works. Worth a try.

[tomlee59]

The Tools section allows you to mux elementary streams together with a time offset you can specify. I have not used it with AVI files, but it would be very easy for you to find out whether it works as you need it to.

[Dr. Macenstein]

The Tools section allows you to mux elementary streams together with a time offset you can specify. I have not used it with AVI files, but it would be very easy for you to find out whether it works as you need it to.

hmm..

How exactly would you do that?
I tried selecting a QT movie for the movie, then the same movie for the audio1, then chose AVI + audio under "Mux As", and I cannot enter any values in the "sync" field".
Is that where you would change it? It won't let me.

Incidentally, if it DID, and you wanted the audio to start half a second later than it does, what would you enter there?
0.5?
-0.5?
1?

thanks!

-The Doc

[Case]

It won't let me.

Only MPEG with current version, if you read between the lines.

Incidentally, if it DID, and you wanted the audio to start half a second later than it does, what would you enter there?

500 (milliseconds)

[tomlee59]

Yeah, the guide is a bit mysterious in its wording. It explicitly mentions the sync offset parameter for mpeg muxing, and then talks about the mux tool also working for avi. But it doesn't explicitly state that the sync parameter is absent in that case (nor does it say it's still available, either). It actually sounds like you *might* still be able to dial it in, given what Dr. Macenstein wrote.

Dr. Macenstein: You are asking the tool to mux two things that are already muxed. As I mentioned earlier, you want to mux *elementary* streams. That means a VIDEO ONLY file, and another AUDIO ONLY file. "Mux" means "to combine" here. So if you give it a QT movie (that already contains video + audio) as a video file, and also give it that SAME thing as an audio-only file, the tool will balk.

Again, I repeat: Ask the muxing tool to mux only elementary streams. I suspect that it will then allow you to type in a value in the sync field. Give that a try and report back.

[tomlee59]

Oh, also, I think that Case got the sign wrong: If you want to delay *audio*, I think that the number (in milliseconds) has to have a negative sign. It's precisely the opposite of what VLC expects in its prefs. Btw, I routinely use VLC to figure out what the right number is, and then I just paste that into ffmpegX's muxing tool, with the opposite algebraic sign.

[tomlee59]

Well, I went home and tried it, but indeed you can't specify a time offset in the avi mux tool, even if you feed it truly elementary streams.

You'll have to use plan B.