letterboxed reference encode to no-letterbox causes artificially poor metrics? #169
Description
This may not be an issue with ffmetrics but a file mastering error. Can someone confirm?
Source: 1920x1080 AVC, possibly incorrectly mastered without anamorphic flag checked. source AR is 2.2:1
Transcoder: using handbrake, av1-svt 10-bit, RF22, preset 8, anamorphic settings auto-detecting and setting 1920x872 output, no other parameters.
Output file (5 min test) in ffmetrics reads as PSNR 20, SSIM 0.83, VMAF 4.9
Visually inspecting the output file - definitely not a 4.9/100. Looks good, I need to play with film-grain settings but it's definitely in the 90's for VMAF.
Tried re-encoding, same settings but turned off any scaling / anamorphic detection. Net file size was almost twice as large (probably since all the letterboxing was now encoded as black space).
Output file in ffmetrics reads as PSNR 43, SSIM 0.98, VMAF 94 - more like I would expect.
So, what can be done to fix this?
-can I "tell" ffmetrics that the reference is letterboxed? like override the metadata on the reference file?
-can I "tell" ffmetrics to add letterboxing to the output file if the AR doesn't match?
-do I need to "fix" the reference file's metadata prior to testing in ffmetrics?