[XviD-devel] iDCT cooefficients different...

[Winnie Weber]

>The standard allows (I)DCT coefficients to slighty differ from
>reference implementation, as far as I know, +-1 is the threshhold, so it's
>rounding effects are covered, but "calculation errors" are not. 

Hm, very interesting to hear.....

What about a sequence where the 'correct IDCT value should be '0, but the
MMX version yields '1' for a duration of 180 p-frames?

In fact, we have this effect here: The image is getting worse, because
the ('wrong') MMX values of 1 add 'something' to the image which is
NOT correct. And 180 frames is a LONG time.....

At next I-frame, we notice a 'hard' picture pop, if we get back to the
'correct' picture.

In a word, getting 0 or something different from 0 in IDCT is very 
important, isn't it?

Winnie

-- 
GMX - Die Kommunikationsplattform im Internet.
http://www.gmx.net