[XviD-devel] Global Motion Compensation

[Michael Niedermayer]

Hi

On Tuesday 22 October 2002 11:34, Christoph Lampert wrote:
> Hi,
>
> two questions for the experts, since I started to look at GMC again but
> have no reference material (there's no DivX5pro for Linux and micro$oft
> reference software doesn't compile).
momusys does compile on linux

>
> 1) What parameter models does DivX5 support for GMC encoding/decoding
>   (affine, 4?, 6?)
LOL

translation only (=1)
but they transmit it as several warppoints, at least they did in the past, 
havnt checked the latest version, that means the 2nd one is allways (0,0)

>
> 2) What parameter models does ffmpeg support for decoding
>   (there's no encoding, yet, right?)
no encoding
decoding support is complete that means 3 points max as the standart only 
allows 1,2,3 for GMC, 4 points is only allowed for sprites

>
> 3) How much work would it be to add GMC decoding to XviD decoder API-3?
>    I guess it's the only feature missing to be a full Advanced Simple
>    profile decoder and for testing I would love to be able to use
>    xvid_stat.
hmm advanced simple allso requires the error resilience stuff IIRC (i might be 
wrong though)

btw, iam not sure if GMC encoding with >1 warp point is such a great idea, the 
speed loss is huge for decoding and that would make the files unplayable on 
older CPUs

btw: 
1 warp point  -> translation
2 warp points -> means translation+rotation+scaling
3 warp points -> affine
4 warp points -> perspective (not allowed in GMC)

[...]

Michael