[Ffmpeg-devel] Snow?

[matthieu castet]

Hi,

Michael Niedermayer wrote:
>>From google all I've found out is 
>>that it's an experimental wavelet codec written by the ffmpeg team. What
>>kind of wavelet transform does it use? Daubechies? Symmetric? Does it
> 
> 
> a symmetric biorthoginal integer approxmation of the 9/7 daubechies wavelet
> 
> 
> 
>>use motion vectors? 
> 
> 
> yes
> 
> 
> 
>>3D wavelets? 
> 
> 
> no, normal 3d wavelets are simply a very bad choice for video compression, 
> there are other lifting based temporal transforms which do work well, but 
> they add some delay, higher memory requirment and they would slow snow down 
> further
> 
> 
> 
>>Are there any license/patent issues?  
> 
> 
> iam not aware of any patents which cover it except one from IBM which IIRC 
> will expire in a few month if it didnt already
> if you want a certainly patent free codec you have no choice except using one 
> which is older then the expiration timespan for patents
> anyone who claims that a codec which is less old to be patent free is lying 
> the number of patents is so huge that checking them all is simply not 
> possible
> 
> [...]

Somebody posts a topic about snow in dirac forum [1] in november 2004 
and a developper asks information about snow.
I copy and pastle your post, and he replies  :

"FWIW I've just uploaded a mod so that Dirac can use a range of wavelet 
transforms, including the approximate Daubechies (9,7) one. As far as I 
can see from the snow code, the choice of wavelet filter is a 
compile-time selection.

I don't know what the patent position with snow is, because there's no 
documentation of the algorithm, so it's hard to tell where it might 
infringe prior art. As far as I can tell from the code, it's similar in 
overall structure to Dirac, but less flexible in terms of chroma 
formats, block sizes and temporal prediction formats. We've not done any 
tests to compare quality, though. Perhaps someone can have a go?

Thomas "


Matthieu

[1] http://sourceforge.net/forum/forum.php?thread_id=1172641&forum_id=353620