23.97 to 29.97

[rjc7394]

How do you convert this? Won't the tone change if you do this?
GSPOT tells me my first video (MPEG1) is 23.97 Pics/sec and 29.97 FPS. I guess this was pulldown? So I demuxed this audio and muxed it with my second video: same video, different format (AVI) with 29.97 FPS. It stayed in-synch for a while then went out-of-synch. How do I get the first audio track in-synch with the second video?

[bond]

generally its better to change the framerate of the video to match the audio than changing the audio, as the later means quality loss as you need to reencode while the first is lossless

if you want to change the length of the audio to match the video you can use besweet

[Awatef]

Well, obviously it's not a framerate problem if you're talking about the same video but with framerates as far away from each other as 23.976 and 29.97.
I suggest you note the place where the audio goes out of sync and see why it is so in the video part. It's most of the time a matter of a few frames that are missing in one of the 2 files.
So if you find the audio to lag behind in the AVI, the AVI has more frames than it should, so look for the culprits and cut them away with VirtualDub.
If you find the audio to come after the video, your AVI is missing frames. Here you cut your AVI into 2 parts, the regular part, and the part where the audio is out of sync. Then you change the audio delay in the 2nd part so that it becomes in-sync. Then you put both parts again together.

[rjc7394]

But GSPOT says both video framerates are 29.97. Why would it start in-synch then go out-of-synch for the rest of the video if I swapped the audio from the MPEG1 and muxed it with the AVI? The MPEG1 audio is 23.976 pics/sec (which I'm not sure what that means) and fps=29.97. Both videos have fps=29.97.

[Awatef]

Well, I explained to you why it goes out of sync all of a sudden: there are some frames missing in the one or the other file in the middle. This does not have an influence on the framerate!
Example:
One clip has 2500 frames and 29.97fps: the duration would be 83.4 seconds.
The other clip has 2505 frames and 29.97fps: the duration would be 83.6 seconds.
So this 5 frames difference is enough to make a 200ms gap in the audio which is very noticeable (who thought the human being is so sophisticated that it could notice differences as small as a tenth of a second!)
So your mission is to remove that gap or to introduce one in the middle of the file where the sound begins to get out of sync!

PS: There is actually no audio framerate. When you see such a term, it actually means audio corresponding to an X fps video, since audio doesn't have frames.

[nickolasemp]

if you want to change the length of the audio to match the video you can use besweet

How could I do that? Thank you in advance..
Or could I change x264's framerate somehow so as to avoid re-encoding?

[nickolasemp]

I used BeLight although its soundtouch doesn't work at all... I entered from 7135 to 6849 and nothing happened. The audio remained the same... I've also used from 25000 to 23997 but still nothing.

Perhaps I should tll you that I have an mp3 as an input and a aac file as an output.