[MEncoder-users] Pulsating I-frames (keyint)

[nicolas.hesler at sheridanc.on.ca]

Because I had started going off on a tangent in my previous thread on B frames and GOP, I've decided to start this thread to address the specific issue started at the end of that thread.

http://lists.mplayerhq.hu/pipermail/mencoder-users/2007-June/006165.html


I'm trying to find a *sweet* highest quality mpeg-2 DVD encode for 24fps cartoon content.
I've noticed that on certain videos,  pulsating occurs on keyframes (I-frames),and especially visible in darker picture areas.  I adjusted lavcopts  vi_qfactor=0:vi_qoffset=0.1 (or as zeroed as possible) which seemed to *slightly minimize the pulsating.  After much shooting in the dark, I discovered that by changing lmin to a higher value (lmin=4 or lmin=5), I was able to eliminate the pulsating effect.  From what I understand, however, this decreases the overall quality (while increasing compressibility) but I'm aiming to get the best quality possible. 

1.  Can someone help me with other parameters that might solve the issue in a different way? (From what I gather it has something to do with manipulating quantizers? But with so many parameters and so many that seemingly affect one another, I don't know where to begin.)

2.  Are there drawbacks to setting vi_qfactor and vi_qoffset to the values I chose? (Am I sacrificing quality?)

Thanks, in advance

Nicolas