In generic.h264 profile configuration, I'd like to see support for the Single Pass - Quality Quantizer Average mode, also known as the "CRF Mode".

It will encode with an average quantizer instead of a constant one. To be more precise, this mode encodes at a constant rate factor (CRF). The so-called "rate factor" is simply a different metric for quality. This suits human perception well. For example it will raise the quantizers in "fast" scenes where the loss won't be visible anyway and lower the quantizers in "slow" scenes.