Transcode failure on iOS 17

[slimbuck]

I am raising this for visibility and in hopes others have found a solution.

Our users are reporting random failures of basis transcode on iOS 17.0.

It looks likely a regression in safari, I have reported the issue here:

https://bugs.webkit.org/show_bug.cgi?id=260252

Since iOS 17 is now released we may be forced to find a workaround.

[slimbuck]

Having test a little more, it's the call to file.transcodeImage on the final/smallest mipmap level which fails:

• only in basis format (ktx2 seems fine)
• compressed with ETC
• with no alpha channel
• larger images seem to fail more often (128x128 don't fail, 256x256 fail 1 in 10, 512x512 1 in 2, etc)

To reiterate, these failures are likely to be an issue with Safari 17 WASM engine, but we are trying to find a possible mitigation from our end.

[Ben-Mack]

Seem like you have found workaround for this problem: https://forum.playcanvas.com/t/important-basis-on-safari-17-0/33145

We found that recompiling the basis module with the latest emscripten toolchain seems to mitigate the issue

@richgel999 Can you update a version compiled with latest emscripten toolchain?

[richgel999]

@richgel999 Can you update a version compiled with latest emscripten toolchain?

Yes - no problem.