u/egosumumbravir

For various reasons I've been attempting to determine a new workflow for dealing with media files and optimising storage requirements vs quality.

I've been comparing different settings and software - Fastflix for it's built in easy handling of HDR10+ & Dolby versus Handbrake. I'm far more interested in NVENC than CPU as the reasons I can't just pop out and buy a couple hundred TB of storage are the same reasons I can't just pop out and buy a TR 9995WX.

Anyway, as far as I know, both Handbrake and FastFlix are based on FFMPEG. Which in theory means that with the same settings, the outputs should be the same. However, analysis with FFMetrics v1.7 suggests something very different - Handbreak scores notably higher on VMAF for basically every bitrate, but also loses dramatically on PSNR, SSIM & XPSNR.

This has me thinking that HB is doing something under the hood that FF does not. I've been searching around to see if HB will tell me the FFMPEG command line it's doing without success. The resultant log file is pretty substantial, but I believe the relevant section from the encode log is this:

"Video": {
    "Encoder": "nvenc_h265_10bit",
    "Level": "auto",
    "Bitrate": 6000,
    "MultiPass": false,
    "Turbo": false,
    "ColorRange": 2,
    "ColorMatrixCode": 0,
    "Options": "",
    "Preset": "slower",
    "Profile": "auto",
    "HardwareDecode": 4
  }

Compare to the FF command line here:

NVEncC64.exe --avsw --device 0 -i TEST.1080p.SOURCE.mkv --video-metadata clear --metadata clear --chapter-copy -c hevc --vbr 6000 --bref-mode each --preset quality --tier high --lookahead 32 --no-aq --level auto --chromaloc auto --colorrange auto --colormatrix bt2020nc --transfer smpte2084 --colorprim bt2020 --master-display G(8500,39850)B(6550,2300)R(35400,14600)WP(15635,16450)L(10000000,1) --max-cll 0,0 --dhdr10-info copy --dolby-vision-rpu copy --dolby-vision-profile copy --output-depth 10 --multipass 2pass-full --mv-precision Auto --avsync cfr --audio-copy 1 --audio-metadata 1?language=eng --audio-disposition 1?default --tune uhq -o TEST.1080p.SOURCE-FFLIX_6000kbit.mkv

I'm hoping someone can offer me insights as to what I'm missing. AFIK, "slower" preset (HB) is equivalent to -P6 and "quality" preset (FF) is -P7. I've been using NVEncC over NVEnc in fastflix as it's been delivering better VMAF scores.