[MEncoder-users] Re: vf_decimate vs 24p->60p content

[Rich Felker]

On Wed, Dec 21, 2005 at 10:42:24PM -0800, Scott W. Larson wrote:
> Rich Felker wrote:
> 
> >On Wed, Dec 21, 2005 at 04:16:15PM -0800, rob pfile wrote:
> > 
> >
> >>so i tried vf_decimate on my tv show, but it didnt work so well. so i 
> >>instrumented the code and discovered that it wasnt actually dropping 
> >>very many frames.
> >>
> >>   
> >>
> >
> >Yes, you'd have to tune the thresholds. :(
> > 
> >
> 
> The best decimate parameter I've found so far for turning filmed 720p 
> content into 24 fps is "decimate=-1:50:1000:.001". That's the only 
> filter I use.
> 
> It's still not perfect. Oddly many duplicate film frames have greater 
> differences than non duplicate frames and can easily throw decimate off 
> the pattern, especially in dark scenes. When that happens it's ugly.
> 
> This seems to be less of a problem with Fox programs since they're 
> encoded by the network instead of being reencoded at your local ABC 
> station. I think the ABC stations' encoders are trying to keep a 
> constant bit rate and end up encoding extra detail in the duplicate 
> frames making them less identical.
> 
> It's a shame they didn't include a "repeat_progressive_frame" flag in 
> MPEG-2. :(

They did. It's called a no-change P frame. :) However no one uses it.

Rich