[MPlayer-users] Fractals and wrong colors on H264-Video

[Loren Merritt]

On Thu, 20 Oct 2005, Ergzay wrote:
> On 2005/10/20, at 9:56, Hanno Böck wrote:
>
>> Trying out this video:
>> http://images.apple.com/movies/us/hd_gallery/gl1800/480p/BBCMG_Andes-r2_480p.mov
>> I get really bad fractals all over the video, along with wrong colors (pink 
>> rectangles).
>> I'm using current cvs version of mplayer.
>> 
>> Can anyone confirm this?
>
> The problem is most definintly with mplayer or ffmpeg. I tried playing with 
> quicktime and plays beautiful. I get the horrizontal band across the middle 
> as well as an effect that looks like what happens when you have 
> -hardframedrop on and you lose lots of frames.
>
> Ergzay

The bug is in apple's encoder. The H.264 reference codec displays the same 
artifacts as ffmpeg does.

As for what the bug actually is: probably a desync in intra prediction.
The artifacts appear first in I-frames, where the left edge of the screen 
is correct, and the DC of both luma and chroma gradually drift as you 
approach the right edge of the screen. (Since each intra block is 
predicted from the neighbors, a small error will be compounded >50 times 
after the width of the screen). The banding appears because this file 
uses multiple slices, which are coded independently and thus drift 
independently. The blocks in P-frames are just the same artifacts after 
being broken up by motion compensation.

--Loren Merritt