Gray line at the bottom of the frame

[kornelski]

Describe the bug
Encoding adds an artifact at the bottom edge of the image

To Reproduce
Encode this image:

Expected behavior
Pixels on the left side of the last line should all be white.

Required Information
Rust 1.55. x86-64 macOS 11.6. NASM version 2.15.05 compiled on Aug 29 2020. rav1e 0.5.0-beta.2

[barrbrain]

I was able to reproduce the issue with the default configuration of rav1e binary. Inspecting the output in AOM Analyzer, we see that the artifact is contained within a 32x64 block that straddles the lower boundary. Will need to look deeper to identify why the distortion occurs in this case. It is also notable that the frame dimensions are not multiples of 8.

[tdaede]

Not necessarily related but it's also interesting how bad the decision is in terms of distortion. The ringing is pretty severe.

[KyleSiefring]

Is distortion being measured in transform domain during partitioning? That might be what is giving bad results.

[KyleSiefring]

Is distortion being measured in transform domain during partitioning? That might be what is giving bad results.

    let use_tx_domain_distortion =
      config.tune == Tune::Psnr && config.speed_settings.tx_domain_distortion;

Doesn't look like it is.

[barrbrain]

It looks like the underlying cause is that our distortion measurement at the boundary expects input frames to be padded.

[tdaede]

We've merged a fix that fixes the image in this issue.

I've also managed to construct a worst case image that isn't fixed even by the merged fix, I've filed issue #2823 for it. This one isn't really a logic error like our merged fix, but is just a natural result of our edge conditions. The best solution I have so far to fix #2823 also causes metrics losses in non-worst-case pictures, so it's unclear if it's an overall improvement. Let me know if you see any actual real-world pictures that still cause artifacts.