[XviD-devel] option for GMC with 1 warp point

[Christoph Lampert]

On Fri, 3 Sep 2004, glfinish wrote:
> My suggestion is to have a 'reduced GMC quality' mode that will make 
> xvid GMC encodes
> play correctly on this chip.
> I did the necessary modification to the 1.0.2 source tree.
> I tested the encoding with this mode on a real player -- it plays correctly.

Hi,

have you also tested if enabling this mode is beneficial to encoding 
efficiency in any way? Because, XviD (of course) had 1-point GMC in the 
beginning, but it turned out to be plain useless. 1-point GMC can 
encode translational-only camera motion at the expense of 1 extra bit per 
MB. But translational motion is already easily captured by block motion 
ME, and due to prediction and differential encoding, this comes 
essentially without any bit penalty. 
So, instead of adding 1pt-mode, it's simpler to just switch GMC of, get 
the same results (in terms of quality) and have no problems with 
compatibility at all. 

gruel

P.S. IIRC, even DivXnetworks doesn't recommend actually using their 
1-pt-GMC.