[XviD-devel] scene change detecting in Bframes mode

[Christoph Lampert]

On Sun, 18 Aug 2002, Radoslaw Czyz wrote:

> > we have to get rid of the image_mad method to detect scene changes
> > in B-frames mode. This makes too many mistakes... And a B-frame where
> > indeed an I-frame should have been set is ugly.
> 
> Oh yes, I wanted to ask: do we have any scene change detection in
> bframe mode? I ask because in my encodings, there were I frames only
> every 10 seconds + a series of i-frames when people were shooting at
> each other in Matrix lobby. It was wrong, anyway.

Yes, we have, but it's MAD-based and not too good. Search for

image_mad

in encoder.c, that the line where the check is. I had to lower the
threshold from fixed 30 to 20, otherwise I had hardly any keyframes at
all. 

> I was thinking about it and that's what I think:
>  - when we encode a 'future' P-frame, we should use normal I-frame
> detection method


The problem is: "normal I-frame detection" is a full P-frame motion
search and the result is useless afterwards, exept for I-frame yes/no.


We might want to go somehow histogram based, that's more reliable against
motion than image_mad. 

Christoph 

-- 
Christoph H. Lampert chl@math,uni-bonn,de | Diese Signature wurde maschi-     
Beringstr. 6, Raum 14 Tel. (0228) 73-2948 | nell erstellt und bedarf
Sprechstunden: keine, aber meistens da    | keiner Unterschrift. AZ 27B-6