progressive scan PAL to NTSC (not necessarily progressive scan) suggestion needed

[leonid_makarovsky]

I have an AVI file that I captured from PAL VHS. The source there is film (top and bottom fields are the same). The end result should be an NTSC DVD. Not necessarily progressive scan one.

One solution is very simple. Convert 25fps AVI file to 23.976fps AVI file with AssumeFPS(23.976), stretch the audio and feed it to an MPEG encoder.

However, I do notice that the sound is rather slow.

The other solution is to make regular PAL to NTSC conversion. Something like:

AVISource("pal.avi")
AssumeFrameBased()
AssumeTFF()
TDeint(mode=1,order=1,type=2)
LanczosResize(704,480)
ChangeFPS(59.94) # Use replication...
#ConvertFPS(59.94) # ...or interpolation to change to 59.94p fps
AssumeFrameBased()
AssumeTFF()
SeparateFields()
SelectEvery(4,0,3)
Weave()

The sound will be the same, but the quality of course won't be the same. I'm looking for suggestions.

--Leonid

[stickboy]

You can try using the internal TimeStretch filter to stretch the audio while preserving the pitch.

[manono]

Hi-

That assumes that it has the correct pitch to begin with, which is by no means guaranteed. In most cases, slowing it back to 23.976fps without keeping the pitch will restore it to the way it sounded originally. My understanding is that when converted to PAL, the audio is usually not pitch corrected, but winds up a semi-tone higher than the original.

I'm assuming the source was originally 24fps film before being converted to your PAL videotape.

I'd definitely go with the AssumeFPS(23.976) solution.

[leonid_makarovsky]

Hello,

>That assumes that it has the correct pitch to begin with, which is
>by no means guaranteed.

Yes, it has the correct pitch.

>I'm assuming the source was originally 24fps film before being
>converted to your PAL videotape.

No, this is incorrect. This is a musical concert (for refererence Black Sabbath - Cross Purposes Live double pack VHS / CD). I played the CD and VHS back to back. The speed was exactly the same. And yes, this is a progressive footage. The only interlaced piece was the running credits at the end while the rest of the footage was still progressive. In addition to PAL double pack I do own the NTSC version of the double pack. NTSC version is also synched to the CD. The NTSC version is NOT a progressive scan one. It does NOT have 3:2 pulldown pattern at all. I looked closely at the NTSC version and noticed that each field (not a frame - a field) have 2 original PAL frames combed together.

>I'd definitely go with the AssumeFPS(23.976) solution.

Would you still go with AssumeFPS(23.976) assuming that the 25fps is a correct speed?

Oh, and by the way, the reason I don't go with NTSC VHS is 'cause PAL VHS has way better image quality and a WAY better sound. That makes me think that NTSC VHS was recorded from PAL VHS commercially on the fly.

--Leonid

[manono]

Hi-

Would you still go with AssumeFPS(23.976) assuming that the 25fps is a correct speed?

I would, but now that the picture is clearer, so-to-speak, I can see where someone else might do it another way. For me, clean detailed frames are paramount. It might be argued that there's not much detail to begin with when the source is VHS. But I see so many PAL to NTSC DVDs all full of nasty blended fields, that I'll always take a progressively encoded DVD over anything else. Since you saw the bad NTSC version of the same concert, then you know what can happen. In addition, by encoding at 23.976fps and running pulldown afterwards, the available bits are spread among fewer frames, when compared to encoding at 29.97fps, resulting in higher quality.

As for the audio, it looks like stickboy's suggestion was the better one. I don't know how to do what he suggested, although I don't guess it's too hard. I suppose you could do the same thing (slowing the audio, and at the same time preserving the pitch) in a good WAV editor. I only have Cool Edit Pro, and it does a very bad job at that, making the audio all warbly.

[leonid_makarovsky]

Thank you, Manono.

I'll do what you suggested.

--Leonid

[Mug Funky]

hmm. probably the best solution is the "changefps(59.94).separatefields().selectevery(4,1,2).weave()" approach. this way you don't get blends (which hurt compression and give a smear effect which is more a feeling than a definite visible problem when you're working with film speeds).

though if you're going to DVD bitrates, there's no reason not to field-blend unless your destination format is a progressive screen (in which case VHS will look shitty no matter what) - a good encoder can manage blended fields at high bitrates, and the only people it annoys really are us encoders...

of course, you could make a PAL DVD of it :)

yeah, i'd say go the changefps route rather than the convertfps route.