Could you list the TOP most important parms for x264 ?

Thank you. Can I assume the first ones are the most important ?

If your goal is to improve quality at the cost of everything else (encoding time and bitrate), then I would use CRF, a custom CQM (such as *.mp4 guy's HRM matrix or the Prestige matrix, both of which can be found here) with AQ and avoid trellis. These are the settings I use: Code:

Here's a test I did a few days ago on 40,000 frames of a DVD movie (denoised with FFT3Dfilter). The "base" setting was --ref 16, --subme 7, --no-fast-pskip, --me umh, and so forth. To be exact: --trellis 2 --merange 64 --subme 7 --bframes 16 --ref 16 --no-fast-pskip --b-pyramid --partitions all --aq-strength 0.5 --8x8dct --me hex --bime --b-rdo --mixed-refs --direct auto --progress --weightb --threads 2 --thread-input --pass 2 --bitrate 1000 --deblock 0:0 Here is the loss in quality, respectively, for each of these changes: --ref 12 0.07% --ref 6 0.15% --ref 2 3.07% --ref 1 7.01% --trellis 1 3.12% --subme 6 1.48% --no-fast-pskip removed 1.43% --merange 32 -0.01% --merange 16 0.11% --me hex 1.70% High --ref values are quite literally useless on non-animated material. --trellis 2 proves to be pretty useful, and --subme 7 proves to be relatively ineffective: half as useful as --trellis 2 and about the same as --no-fast-pskip. --me umh also seems to be similar, but it halves encoding speed. --merange seems to be totally useless on most standard-def material.

Sagittaire measures it in % of bitrate at same PSNR, which is an OK way to do it. Dark Shikari uses his own formula based on SSIM ( 1/(1-SSIM) ), but it doesn't mean much as such.