QUOTE (Kamedo2 @ Jun 3 2013, 19:16) <{POST_SNAPBACK}>
In case quality increase is minimal per bitrate increase, do not increase the quality and save the bit. In case bitrate increase is minimal per quality increase, increase the quality, at the cost of very little more filesize. Wikipedia has the article of rate–distortion optimization.
I see. Sure in an ideal world --cvbr auto should be according to rate-distortion optimization. Unfortunately we don't really know the rate-distortion optimum point. The situation is a bit similar to the choice of -Vn where it's pretty personal where to put the sweet spot. That's not exactly the situation though because I know a bit about --cvbr level dependent quality improvement and I have tried to share a bit of that in the documentation.
As for --cvbr auto: IMO -V5 and -V4 users are very aware of low bitrate, so I use a setting that yields only a small avg. bitrate increase. Quality improvement for samples like eig can be very audible though.
-V3 and more so -V2 users are much more quality aware and less sensitive to a somewhat higher avg. bitrate, that's why I allow for --cvbr 3 resp. nearly 5 here. This way probability for improvement of any issue is much higher, especially when using -V2 --cvbr auto. For -V1 and more so -V0 a pretty high --cvbr level 6 and higher can be used while keeping avg. bitrate increase small.
Individual needs may be different, that's why I gave an imagination for any --cvbr n which -Vx levels are most interesting to be used together with --cvbr n.
To me this makes sense, but I welcome any discussion about it.