[FFmpeg-user] Proper way to reverse PAL Speed up?

Bernd Butscheidt bbutscheidt at yahoo.de
Mon Feb 4 15:20:31 CET 2013

> From: Carl Eugen Hoyos <cehoyos at ag.or.at>
>To: ffmpeg-user at ffmpeg.org 
>Sent: Monday, February 4, 2013 12:00 AM
>Subject: Re: [FFmpeg-user] Proper way to reverse PAL Speed up?

>So why are you targeting a frame rate of 24000/1001 
>instead of 24fps?

Because from what I've learned even BluRay are actually 23.976 and not pure 24fps like cinema. However, 23.976 is nearly 24 fps, so even I don't bother the difference and ntsc film is a well spread standard. But I wouldn't assume that the audio offset I worry about derives from not choosing true 24pfs but 23.976? If you like, I can add examples targeting real 24 fps.

>But are you sure that the pitch wasn't changed 
>by 4% for tv transmission? 

No, to my knowledge you can't be sure. Normally I would aspect the pitch not be changed but I wondered many times why American actors have these high voices ...

> I wonder if it is 

>a good idea to change the playback speed with 
>FFmpeg, especially since you can change it at 
>playback time anyway.)

I cannot change the speed on my hardware movie players. They only accept true PAL or ntsc input and play them at the speed proposed with it. And all I tried so far with vlc & Co which means changing speed during playback time lead to poor audio quality. And it would need quite a strong PC to be used to play movies like this. 

In addition I wouldn't wonder if the combination of asetpts and aresample keeps the pitch.

Maybe speeding up or slowing down a video is a senseless task anyway. Still I wonder if I apply the filters setpts and asetpts the right way, which I thought could be applied for this.

Kind regards

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