[MEncoder-users] Experiences of video encoding

[Mathieu Monnier]

Some random thoughts/questions:

  * Quantizer scales in XviD/lavc and x264 differ. Going from 1 to 51 by 
step of 2 in x264 is fine, but doing so in mpeg4p2 isn't, because the 
quantizer scale is too coarse around 1. I would do 1, 2, 3 and 4, then 
by step of 2 till 16, then by steps of 4 or more. You'll do less tests 
that way, and the RD points will be more smoothly spread along the RD curve.

  * As Corey pointed, P/B quantizer offset is really important. You 
should at least use the same for XviD and lavc. For x264, the default 
one is good.

  * Why do you denoise the video ?

  * for XviD, I don't know if trellis & chroma motion are enabled by 
default. If not, you should do so.

  * XviD should be better, PSNR wise, for h263 quantization type.

  * The cartoon option is - as its name says - for cartoon/anime 
content. It favorizes the skip slightly. It has been implemented without 
any regards to metrics, so it's not surprising it doesn't do well in 
your tests.

  * How do you compare PSNR figures with different resolution ? In what 
resolution do you compute the PSNR. How do you conclude that native 
resolution is good up to 25, then resolution should be lowered ?

  * Your plots are mostly unreadable ( too many curves, not enough 
colors ), and hard to visualize in Firefow, imho ( the original size is 
too small, and zooming prevents you from seeing the big picture ).

  * What does the curves PSNR HD/native size try to show ?

Regards,

Mathieu