IVTC of 29.97 downloaded MPEG

[DRP]

Why is it sometimes not possible to IVTC a progressive 352x240 downloaded 29.97 MPEG with a view to doing a conversion to PAL?

I've just tried this today and the end result was a file that was way bigger than the capacity of the CD-R to which I intended to burn it and a progressive audio sync problem (yes I did adjust the audio for the NTSC -> PAL conversion).

Both problems are examples of the IVTC not working - ie. frames *not* being removed when they should have been. Why did the TMPGEnc IVTC *not* work?

[Gazorgan]

There are a number of reasons. One is it was never a 23.97 fps source? There's nothing to IVTC....

Another is it's a non-stnadard pattern, and TMPGEnc only IVTC's the standard pattern. You can try VDUB or AVISynth to do the IVTC then frameserve it.

[DRP]

Okay I've tried that. I used the "Reconstruct from fields - adaptive" option in the IVTC section of VDub and it appears to have worked - a little too well if anything. It appears to have done an IVTC but... and here's the weird thing... I frameserved it through to TMPG and did the re-encoding with a specified output of 25fps.

The resulting MPEG-2 file multiplexed with the MP2 that came out of the original MPEG-1 file I started with seems to play perfectly with no audio sync problem or anything. How can that be possible? How can you IVTC a 29.97 MPEG-1 *and* convert it to 25fps and *not* have an audio sync problem when you multiplex it back together with the original unmodified audio track that came out of the original 29.97 NTSC MPEG-1 file?

Is the IVTC option I used in VDub something special or tricky?