Converting PAL audio to NTSC Film

[zambelli]

I have some progressive PAL material that I'd like to convert to NTSC Film by doing a 25 --> 23.976 fps slowdown.

The lazy way to convert the audio would be to assume a sample rate of 46034Hz and then re-sample to 48000 without any pitch correction. However, if I could do a high quality time stretch (with preserving pitch) that sounds (almost) indistinguishable from the original, I'd much rather do that. I've searched the forum for past experiences, but a lot of the threads were pretty crusty - from 2-3 years ago - and I'm sure many tools have made progress since then.

Are there any tools that will do a quality 25-->23.976 audio time stretch without noticeable artifacts? Or am I better off just simply slowing down the samplerate and living with the lower pitch?

[Guest]

Why do you want to go to 23.976fps?

[Mug Funky]

soundtouch is very good for 2ch stuff.

however, you'll have to ascertain whether the PAL version was actually a straight resample or a timestretch in the first place. there's a lot of both out there...

if you can find some music from the original soundtrack and compare it to the PAL source you'll be able to tell.

also remember that no matter how good the timestretch, it risks introducing very unnatural artefacts, and there's not much advantage in preserving pitch when tempo is going to be off regardless :)

[edit]

if you're making a DVD, you could also simply resize the video, leave it at 25fps (ie no need to re-encode audio), and use DGpulldown to bump it to 29.97fps. this is probably the nicest solution, but obviously not do-able if you need the framerate to be 23.976

[zambelli]

however, you'll have to ascertain whether the PAL version was actually a straight resample or a timestretch in the first place. there's a lot of both out there...
It was neither. It's original PAL footage.

if you're making a DVD, you could also simply resize the video, leave it at 25fps (ie no need to re-encode audio), and use DGpulldown to bump it to 29.97fps. this is probably the nicest solution, but obviously not do-able if you need the framerate to be 23.976
I've considered that, but I am guessing many DVD players might struggle with interpreting that correctly in progressive scan mode. Would they be able to correctly convert the native 25p to 59.94p? At least we know for sure 23.976p-->59.94p would work correctly in 99.9% of prog scan players (assuming it's flagged correctly).

[Guest]

I've considered that, but I am guessing many DVD players might struggle with interpreting that correctly in progressive scan mode. Would they be able to correctly convert the native 25p to 59.94p? At least we know for sure 23.976p-->59.94p would work correctly in 99.9% of prog scan players (assuming it's flagged correctly). I am not aware of a single player that does not support the pulldown produced by DGPulldown. It relies on mandatory MPEG2 syntax that every player must support. Why don't you make a test disk and try it on a few random players?

[zambelli]

I am not aware of a single player that does not support the pulldown produced by DGPulldown. It relies on mandatory MPEG2 syntax that every player must support. Why don't you make a test disk and try it on a few random players?
The issue is not supporting pulldown - I understand that's common MPEG syntax. But the result of such a pulldown, just like with typical 3:2 pulldown, is a 29.97i decoded stream. It's typically the deinterlacing/IVTC hardware in a progressive scan DVD player (as most are these days) that creates a progressive 59.94p video out of it. Or if the DVD player doesn't, the progressive TV/display needs to anyway. Bottom line: at some point in the playback chain, an IVTC needs to be performed in order to restore the original 25p and convert it into 59.94p. I could be wrong, but my guess is that most average consumer hardware is not capable of detecting a 2:2:3:2:3 pattern in a 29.97i video.

So it's not that I have any doubts that DGPullDown produces NTSC compliant video. It's that I have doubts about how that video gets treated deep in the playback chain.

[dvdboy]

I'm also running into this problem at present wanting to do the best job on a PAL to NTSC transfer.

I have a PAL Digi-Beta of a film, so the footage has been sped up by 4% (?).

Capturing the film as progressive, I have used an AVISynth script to slow the footage down to 23.976fps, which I have then encoded with 3:2 pulldown to take to 29.97fps.

I know BeLight gives you the option to retime from 25000 to 23976 under advanced options but this seems to produce quite 'choppy' audio.

What would be the best way to slow the audio down (and also pitch correct it) so that the audio is 'correct'?

[zambelli]

What would be the best way to slow the audio down (and also pitch correct it) so that the audio is 'correct'?
I ended up using BeSweet for the slowdown, but it's somewhat confusing that there are 2 plugins in BeSweet that support this function: OTA and Soundtouch. I think I ended up using Soundtouch.

In general, stretching audio with mostly dialog seems pretty good, but stretching audio with music can get nasty.

[dvdboy]

Hmm, that's the problem; I've got a short film with music and dialog.

Just tried to use Time Stretch in Soundforge to create a new wav 104.27% the duration, but when I've synced to two files up in Scenarist, the picture is too slow to video.

Might have to give Soundtouch a go, can't remember which one I used last time!