What is iDCT and how it affects encoding DivX ?

[dihelson]

Hello, All,

I'd like to know what iDCT means and what it does, and what's the best one ?
I use Xmpeg 4.5 and Flask 060 and 078.39.
iDCT affects only the velocity of compression or it can affect the QUALITY of the image also ?
If so, what's the best iDCT for my computer , an Athlon XP 2000 ??
I've tried some iDCTs and haven't noticed much difference on them.
The fastest iDCT gives a poor quality ??
What's the BEST of the BEST quality independent of speed iDCT ?

Thanks in advance ,

[khp]

iDCT is short for inverse Discrete Cosine Transform. It's the base of the mpeg-2 decoder, and yes it does have an effect on the quality of the decoded frames. The best one is the Reference idct, it uses floating point calculations, which is slower but more precise than integer or mmx.

But the difference is next to nonexistent. I tested it once, decoding to uncompressed avi files, and I absolutly could not tell any difference between any of them.

I would suggest that you use the 'preform test' function next to the idct selection box, and check if each idct meets spec limits, if it does, it should be perfectly OK.