Since one of the developers let it drop that there's a new hevc decoder in the works, I decided to get ready by doing a bunch of transcodes with Vegas 19 to use as a basis of comparison. My results so far are in a google sheet here:
I used a lossless hevc clip I shot with my a ZcamE2 as the source for all the transcodes and quality comparisons. I used the ffmetrics tool to take all the measurements listing all 3 of the metrics it reports. For consistency with vmaf measurements I've done in the past, I used the latest N4.4 release version of ffmpeg from BtbN to power ffmetrics. Since the decoder is the root of all quality, I ran a bunch of different encodes for analysis. Looking forward to repeating these with vp20 as soon as the new decoder gets here. In the meanwhile, some of the results I got unexpectedly go against common wisdom.