Doom9's Forum - View Single Post - MeGUI - x264/XviD/lavc/Snow encoder with MP4/MKV/AVI output & audio

akupenguin · 27th December 2005, 13:39

Yes, XviD dithers the quants, 50% q2 and 50% q3.
lavc allows a qscale=2.5, and really does it (rounds to the nearest integer quant, but tweaks RD and trellis to get a quality point halfway between qscale=2 and qscale=3).

stax: Notice how your q2.5 is nowhere near halfway between q2 and q3. That's because the q3 half of the frames are lower quality, but most of the details missed there just have to be encoded in the next q2 frame. So overall you don't save many bits, and just lose a little compression efficiency.

27th December 2005, 13:39	#972 \| Link
akupenguin x264 developer Join Date: Sep 2004 Posts: 2,392	Yes, XviD dithers the quants, 50% q2 and 50% q3. lavc allows a qscale=2.5, and really does it (rounds to the nearest integer quant, but tweaks RD and trellis to get a quality point halfway between qscale=2 and qscale=3). stax: Notice how your q2.5 is nowhere near halfway between q2 and q3. That's because the q3 half of the frames are lower quality, but most of the details missed there just have to be encoded in the next q2 frame. So overall you don't save many bits, and just lose a little compression efficiency. Last edited by akupenguin; 27th December 2005 at 13:44.