framerate switcheroo

[AlecWest]

Purists would likely gnash their teeth at the thought (grin). But, there's something I'd like to do anyway and just need to know how to do it properly.

I have a fanfilm (Star Trek New Voyages - "World Enough and Time") that originally came in a high-res H264/MP4 format with a 24fps framerate. I've already created an NTSC DVD ISO, preserving that framerate, and it looks great. But PAL is something else. There's always this teensy jerkiness to it.

Anyhow, since 24 and 25 are so close together (and the switcheroo would be less noticable), I'd like to "speed up" the framerate to 25 to get a non-jerky PAL result. Yes, I know this would shorten the program time of the episode. But I doubt characters would start looking like Keystone Cops with voices sounding like Alvin and the Chipmunks (grin) with a framerate change so slight. What's the best way to "speed up" such a file so the video/audio remain in sync?

[Midzuki]

What the devil is a ``switcheroo´´

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[jagabo]

Speeding up the frame rate from 24 fps to 25 fps is the usual method used by movie studios for film to PAL conversion.

[Midzuki]

So be it.

http://avisynth.org/mediawiki/AssumeFPS

( and maybe http://avisynth.org/mediawiki/TimeStretch as well )

+++++++++

[freebird73717]

Alecwest. I noticed in another thread someone talking about doing a framerate conversion. Here is what they did.

Made and AVisynth script with assumefps(25.00) and encoded to 25fps. Then used dgpulldown and did a custom pulldown with the correct fps ( in this case 24.00 -> 29.97 )

That in essence allowed you to encode at the source fps then add pulldown. Might be worth a try.

from this thread
https://forum.videohelp.com/topic335127

You may experience diffiiculties encoding to MPEG2 with the non-standard framerate 20fps. The solution is encoding to the nearest legal value (like 23.976). To force this in any encoder without duplicating or blending frames (important) you can assume that different framerate in AviSynth with 'AssumeFPS(23.976)' command. This will change video duration correspondingly (all available frames will get different time code) but you can turn duration value back in DGPulldown if you type 20fps for input framerate (instead of actual encoded value 23.976) and perform 20=>29.97 pulldown.

Or if you really want to go to pal you could just do a custom 24.00->25.00 dgpulldown. That way you don't even have to touch the audio.

[Cornucopia]

I'm not sure, but I thought what Alecwest was asking about was how to change MP4 framerates WITHOUT reencoding. If so, that greatly narrows the options. I myself don't know of any apps that'll do that for MP4, but it ought to be possible (much like Restream or DVDPatcher for MPEG2).

However, framerate isn't the only thing that would need to change--there's also resolution. You couldn't do both without reencoding. Even the sly DGPulldown methods require reencoding because of resolution changes.

Also, if you ARE trying to just do a framerate adjustment (in the headers/fields), thereby making all pix run through quicker, you'll also need to do a TIMECOMPRESSION of the audio--to the tune of 4% faster, in order to keep in sync.

Scott

[AlecWest]

I'm not sure, but I thought what Alecwest was asking about was how to change MP4 framerates WITHOUT reencoding. If so, that greatly narrows the options. I myself don't know of any apps that'll do that for MP4, but it ought to be possible (much like Restream or DVDPatcher for MPEG2).

I think DVDPatcher might be the tool I'm looking for. I can easily convert a 24fps MP4 to a 24fps MPEG2 file ... and burn it to an NTSC DVD that plays without jumping. So, I'll do the MP4-to-MPEG2 conversion again ... then try DVDPatcher to see what happens.

Thanks to all who made suggestions. If DVDPatcher doesn't work, I'll revisit them.

Regards,
J. Alec West