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

[Bernd Butscheidt]

----- Original Message -----

> From: Carl Eugen Hoyos <cehoyos at ag.or.at>
> To: ffmpeg-user at ffmpeg.org
> Cc: 
> Sent: Sunday, February 3, 2013 7:12 PM
> Subject: Re: [FFmpeg-user] Proper way to reverse PAL Speed up?
> 
> Bernd Butscheidt <bbutscheidt <at> yahoo.de> writes:
> 
>>  The source is a German TV Recording (ZDF HD) 
>>  broadcast in 50fps. I indeed want to speed down 
>>  to double ntsc-frame rate (asetpts, setpts)


!!! and then drop every second frame to result in standard ntsc film = 23.976  fps !!!!


 
> Why do you think that this is a good idea?

Cinema source is recorded at 24 fps, to make it broadcast due to PAL standard the television stations or all DVD releases of movies are speed up to 25 fps. So films on DVD or broadcasts of movies on PAL-television are about 4 percent shorter than the cinema version.

You can reverse this effect e.g. with mencoder using the -speed option, but mencoder is not supposed to be the future as read in the mencoder user list frequently. 
Avidemux offers such a filter as well, still, the 2.6 version is already very promising but not ready in every point of view.

Since ffmpeg offers new filters which look promising to do this task, I try to do video speedup/ speedown with it. Of course there is "no need" to do such things. But you could argue that it is better to read than to watch television as well .... The simple idea is to play the PAL recordings at the speed they originally were recorded.

But maybe this gives the opportunity to put my question in another way:
Is my way of using asetpts, setpts and aresample a proper way to do with ffmpeg what the option -speed can do in mencoder, which is speed up or down a video without dropping or duplicating frames.

If so, am I right that an offset of about 250 ms is needed to be added to the audio? The samples I provided suggest this but to be honest this doesn't seem right to me.

Kind regards
Bernd