Lossless export result isn't truly lossless

When comparing PSNR, SSIM and rawvideo hash, the exported footage seems to be losing data even if nothing was changed with the original footage in premiere.

Footage used: H.264 | yuv420p | bt.709/bt.709/bt.1886 | 23.976 fps
steps i took:
import the footage to premiere and immediately right click it > export media
Variations i've tried inside Voukoder designer:
encoder: ffv1 / utvideo
muxer: AVI / Matroska
pixel format was set to match original footage (yuv420p, 8bit)

After export i've proceeded to test differences between the original footage and the exported footage using the following:
ffmpeg -i original.mp4 -i rendered.avi -lavfi psnr="stats_file=psnr.log" -f null -
ffmpeg -i original.mp4 -i rendered.avi -lavfi ssim="ssim.log" -f null -

but results seem to differ than original footage.
not sure if this is an issue on Voukoder's side, but i'm wondering if u have any insight on why that happens.

of course, when using solely ffmpeg to convert the original footage to ffv1, the rendered footage showed identical results in every way i've tested, including rawvideo hashes. so my hunch is that something happens within premiere before Voukoder takes over the export process.

Zitat von Vouk

To me it most likely might be the data transfer from premiere / the nle to voukoder pro. That means slight losses can happen, because the video gets always decompressed, send to voukoder pro and then recompressed. but this is the way each nle works. there is no way around it.

That does seem to be the case. after more testing, the only way i was able to get identical results was by inserting the footage as an image sequence with specifically rgb24 as its pixel format, and then exporting the footage as an image sequence again. other than that, whether i use voukoder or just premiere, the export is a bit lossy. definitely an issue on premiere's side, thanks!