converting NTSC 29.97 to PAL 25

[DrP]

Ok, this is a curly one. I have a mpeg of a show in NTSC and want to convert it to PAL format. Frame size is easy enough, but can anyone give me a step by step in how to drop the 29.97 rate of NTSC to 25 for PAL? I know i'm going to have to do either drop 1 in 1.1988 frames (ugly eh?) and this will give a slight jerkiness to the video or do a smoothed blend on a few frames (this is how the TV networks do it).

Curious thing I wasn't aware of, seems there is a bit of timebase mangling going on by TV networks / studios when they do this conversion themselves, an audio clip from the same show shown here in Australia Vs the version shown in the US had the US version 2 seconds longer and with the audio downshifted in frequency... hmmm... I thought networks / studios would have done a better job at it.

TX for any clues on how do do this....

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OK, worked out the audio thing. Seems the show was originally shot on film at 24fps and the easy coversion for networks is just to run it at 25fps when playing on PAL. As far as I can tell, the film was telecined (?) to 29.97 for US TV, then taken in video format to Australia and mangled to 25FPS as the telecining artifacts are still there. Sheesh - how messy can these guys get! Gonna de-telecine it and the bodge the frame rates etc.
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[Rob100]

Yes you are on the right track here. If it was originally shot at 24 fps, slowed to 23.976 fps and telecined up to 29.97 fps then that's easy enough. This is what I would do...

First demux the video and audio and convert the audio back to a wav. Actually you could use VirtualDub to load the MPEG1 and save the wav if you want.

Then increase the audio speed to 25 fps (from 23.976). I always used WaveLab (set ration for 0.9504 (23.976/25)) for this as I found Cool Edit to be very slow. Recently I've been using "OTA" - the best bet it to use BeSweet (go to www.doom9.net for download/guide).

As you suggest then IVTC the video stream back down to 23.976 fps and sync with new audio file. I'd use AviSynth to perform IVTC (use the "selectevery" function) and to speed up the video to 25 fps (use the "assumefps" function) and finally add the new audio track (using "audiodub" function).

Hope this helps.

Rob.

[DrP]

What I ended up doing was this... and its messy but it worked...

I stripped the audio out of the original file with virtualdub, the hex edited the sample rate to 45639Hz to take account of the eventual 23.976 to 25 fps rate change. Next I ran the video thru tmpgenc's de-telecine filter to a 23.976 avi, then fed the video through Virtualdub to resize it with a precise bicubic filter level .6. Virtualdub was used again to change the frame rate to 25fps. I used winamp to downsample the audio back to a nice 44100, and then fed the entire kit back into tmpgenc to recode it. at all stages the video was encoded with huffy to keep the quality as good as possible.

Long but it worked.