can we convert PNG with specified sampling format？

[woshilaiba]

First，thank you for this very helpful tool ！ In my case， convert the png file to avif ，I found that it will generate a pink stripe at the right edge of the png file. It is the same situation in AOMediaCodec/libavif when encoding with the " -y 444" option, but not with "-y 420" or "-y 422" So, i guess it (Chroma Subsampling) is the cause of this little problem.

CLI: cavif -Q 50 test.png the original image for test:

after convert like this( a jpeg for just show what it looks like):

Thank U!

[kornelski]

This crate always uses 444 (highest resolution) color sampling, so it isn't supposed to cause any distortions like this.

Do I understand correctly that you've encoded this image using a different tool and still saw the incorrect line? That would suggest it's a bug in the decoder, not the encoder.

I would prefer to kill chroma subsampling for good. AV1 handles color quite well, and doesn't need to continue the tradition of using a mathematically-dubious hack invented for an analog TV signal from more than a half century ago.

[woshilaiba]

This crate always uses 444 (highest resolution) color sampling, so it isn't supposed to cause any distortions like this.

Do I understand correctly that you've encoded this image using a different tool and still saw the incorrect line? That would suggest it's a bug in the decoder, not the encoder.

I've encoded this image using "avifenc"， the cli is "avifenc -y 444 tray.png tray_avifenc.avif", and using "cavif" with "cavif -Q 50 tray.png" . They both get the incorrect line at the right edge, but It is correct when I encode it with "avifenc -y 422 xxxx.png xxx.avif". I'm not familiar with "Chroma Subsampling", just a guess!

operating system: Windows 10 subsystem for linux

[eugenesvk]

I've read in this blog that the vertical bar is an issue with Microsoft Photos, so might indeed be a decoder issue

Additionally, for avif images created by libavif, Microsoft Photos will have a strange vertical color bar on the right side of the images when the format is set to YUV444

[kornelski]

Yup, I think it's a decoder issue.