Subsampling Fails

[jimbo2150]

Describe the bug
Attempting to subsample colors causes encoding to fail.

To Reproduce
Add --resampling=2 (or any other valid value other than 1).
An error occurs: Failed to compress to VarDCT.

Expected behavior
Produce an image.

Environment

• OS: Windows 10
• Compiler version: various
• CPU type: x86_64
• cjxl/djxl version string: [v0.3.7 | SIMD supported: AVX, Scalar]

[veluca93]

Interesting, what is the image that reproduces this?

[jonsneyers]

I cannot reproduce. On PNG input, it works as expected. On JPEG input, doing lossless JPEG recompression, it does do something that it probably shouldn't do (it encodes something that is the top-left quadrant, upsampled 2x, that decodes to pixels but not back to the original jpeg). I couldn't find a way to make it not produce a jxl file though.

[jimbo2150]

Interesting, what is the image that reproduces this?

Every image I tried causes it to fail.

[jonsneyers]

Default cjxl options?

Are you using the current latest version from git?

(we should bump up the version number because 0.3.7 can mean anything at this point)

[jimbo2150]

I've tried with default and adding other options, nothing worked if resampling is set to anything other than 1.

It is 0.3.7, don't know the hash it was build on. Just using a build from the Discord links. Most don't work but the two I found that do both do the same thing. One appears to have SIMD while the other doesn't. They were both built around mid to end of May.
I can build one this weekend and see what happens.

[jimbo2150]

I just tried Raysar's new build and it works. Possibly the other builds floating around were missing something.

[jimbo2150]

Running into some issues again. Any photo I try to compress with quality below 52 fails.

[deymo]

@jimbo2150 what platform do you need builds for?

[jimbo2150]

@jimbo2150 what platform do you need builds for?

Windows 10, but don't really need it now. Someone just did a build - first one I've seen in a few weeks. I can build it myself, but would need to do it over a weekend. Thanks.

[jimbo2150]

Running into some issues again. Any photo I try to compress with quality below 52 fails.

[veluca93]

Ah, I know what is going on -- try passing --progressive_dc=0 too...

[jimbo2150]

Ah, I know what is going on -- try passing --progressive_dc=0 too...

That worked, but odd that you have to disable progressive decoding.

[veluca93]

Ah, I know what is going on -- try passing --progressive_dc=0 too...

That worked, but odd that you have to disable progressive decoding.

Progressive DC doesn't work with downsampling - but we should not turn it on by default then :)

[jimbo2150]

Also fails on any speed above 7.

[veluca93]

Ah, yes, I can see why that would be the case - we'll make sure to return an explicit error.

[ziemek99]

Any updates on this issue?