Re: [Avid-L2] 29.97 and HD / RANT

For sound, there is no difference for any framerate.

But of course there is. 

We are talking about either 

A) a 24 fps film played back at 23.976 fps, so slowed down

or  

B) a 23.976 fps film played back at 24.000 fps, so speeded up. 

The mix will need to be pulled up or down accordingly, or it will run out of sync with the picture.

For instance, if the film has been mastered to 24.000 fps, there will be 48000 Hz sound deliverables that run in sync with the picture as long as that runs 24.000 fps. If the picture is slowed down to 23.976 fps, the sound clock is then pulled back to 47952 Hz, so it will run in sync with that 23.976 fps picture, and then it is sample rate converted to 48000 Hz. This is commonly done without any correction to the slight change in pitch that is caused during this process. 

Going from 24 to 25 (or vice versa), the pitch change is more significant. A pitch correction always causes some sound quality loss. Some sound post folks will therefore not correct the pitch and put up with the changed pitch. Or they only correct the dialogue, or only the music. More commonly, the process individual stems with different methods, then mix those stems back together.

J