Visual artifacts for DXT-5 textures (black-blocks) in PepperFlash plugin

[mrchnk]

Problem Description:

Sometimes ATF DXT-5 textures decoded with visual artifacts: black blocks

Large textures corrupt more frequently than small ones

That artifact shows up only in PepperFlash plugin (Chromium-based browsers)

Steps to Reproduce:

• Goto https://rawgit.com/mrchnk/FlashPlayerDXT5Bug/master/bin/index.html
• Wait until frame counter stops with something visual like https://i.imgur.com/tntw9JV.png

You can grab full source code and assets from https://github.com/mrchnk/FlashPlayerDXT5Bug

Actual Result: Texture rendered with artifacts

Expected Result: Texture rendered without artifacts

Any Workarounds: Re-upload texture.

It's hard to automatically detect is it decoded normally or not.

Issue tracker link: https://tracker.adobe.com/#/view/FP-4198484

This bug still shows up in chrome version 66 and plugin version 29

OS version: Windows 10 x64, MacOS

GPU: various NVIDIA's and AMD's GPU's including gtx960, gtx970, gtx1070, gtx1080

I would like to start the discussion about that bug and found all affected machine setups.

[jeromiec83223024]

Just looking at our internal bug history, we've only been able to reproduce this with the textures that you provided in the bug.  The ones that we generate and use for testing don't exhibit this problem.

It might be helpful to understand exactly how you're generating those textures.