[MPlayer-dev-eng] Custom soft-telecine patterns

[D Richard Felker III]

On Thu, Mar 17, 2005 at 05:56:18PM +0100, Nico Sabbi wrote:
> Hi,
> reading this thread:
> 
> http://forum.doom9.org/showthread.php?s=b38c32c3b426dec0e3e614a00ef7ba80&threadid=88031&perpage=20&pagenumber=3
> 
> (relevant quote is this:)
> 
> OK, about the dropping... I don't drop anything. Instead I just don't do 
> any repeats for a cycle so that there is one less display frame. So 
> normally, I do (for TFF):
> 
> a) 3 0 1 2 2
> 
> Where bit 0 is RFF and bit 1 is TFF. That makes 6 frames out of 5. Then 
> every 1001 display frames, I use:
> 
> b) 2 2 2 2 2
> 
> So once every 1001 I generate one less display frame.

This is very idiotic, IMO. It will lead to a slight jerkiness every
1001 frames. If you want a pattern like this, it can be done slightly
better (not a whole 5 frames at a time) but it's still a dumb idea
IMO. Why? See...

> it seems that using pattern a) it's possible to telecine 25 fps 
> progressive video to 30 fps,
> and with pattern b) 25fps -> 29.97

Stupid goal. 25fps progressive video was almost ALWAYS sped-up from
24fps film to make a PAL DVD. The solution is to slow it back down and
fix the audio at the same time. MEncoder can finally do this now, with
-speed. Use -speed 24000/25025 to convert PAL to NTSC FILM rates, etc.

> It sounds convincing. Is it really? :)
> 
> If it's so I can extend the mpeg muxer to accept a custom telecine 
> pattern (keeping
> predefined ones such as 3:2 , a) and b)   ).
> 
> Opinions are welcome.

Defining a pattern is stupid, IMO. On the other hand, supporting
arbitrary input framerates to telecine is not a bad idea. But your
muxer should generate the natural pattern itself (there's a way to do
it without following any "pattern", just comparing timestamps and
setting the flags accordingly) rather than having users specify stupid
patterns to it. :)

Rich