Cap crashes on launch with AMD Radeon 780M iGPU (atio6axx.dll, 0xc0000005)

[5401754017]

Cap.exe crashes immediately/repeatedly when using AMD Radeon 780M integrated graphics (Ryzen APU).

Crash details (consistent across 3 different AMD driver versions):

• Faulting module: atio6axx.dll
• Exception code: 0xc0000005 (Access Violation)
• Fault offset: 0x0000000000b4a7fa (identical across driver versions)

Tested driver versions (all crash identically):

• 31.0.22038.0
• 32.0.31021.1015
• 32.0.31021.5001

System:

• Cap version: 0.5.2.0
• GPU: AMD Radeon 780M (iGPU) + NVIDIA GeForce RTX 4060 Laptop GPU (dGPU), MSHybrid mode
• OS: Windows 11

The crash also occurred with webcam "heavy" background blur disabled, and with --disable-gpu flag (no effect, likely because Cap uses Tauri/native rendering, not Electron/Chromium).

Workaround: forcing the app to run on the NVIDIA dGPU instead of the AMD iGPU avoids the crash.

[linear]

CAP-742

[tembo]

This crash in atio6axx.dll (AMD's OpenGL/DirectX driver) at the same offset across multiple driver versions points to a driver-level bug triggered by Cap's GPU initialization path. The fact that forcing the app to the NVIDIA dGPU works confirms the AMD driver is the culprit.

Related context:

Issue #1756 reports a similar hybrid GPU problem on macOS (MacBook Pro with AMD dGPU + Intel iGPU), where Cap was selecting the wrong GPU. The code already requests PowerPreference::HighPerformance when initializing wgpu adapters (see gpu_context.rs:56-58 and crates/rendering/src/lib.rs:155-158), but on Windows hybrid systems the OS may still route through the iGPU driver.

Potential workarounds to try:

1. Force software rendering - Set environment variable CAP_RENDER_FORCE_SOFTWARE_ADAPTER=1 before launching Cap. This bypasses the AMD driver entirely by using CPU rendering (slower but stable).

2. Force DX12 backend - Cap on Windows prefers DX12 when available (lib.rs:147-166). You could try setting WGPU_BACKEND=dx12 to ensure it doesn't fall back to Vulkan, which uses different AMD driver code paths.

3. Windows GPU preference settings - In Windows Settings > System > Display > Graphics, add Cap.exe and explicitly set it to use the NVIDIA GPU (which you've already found works).

For the maintainers:

The crash happens during wgpu adapter initialization or first GPU operation, likely in prewarm_gpu() or the shared GPU context setup. Similar AMD Radeon 700M series driver crashes have been reported in other wgpu-based apps. A defensive approach would be to wrap the initial adapter probe in a catch for access violations and fall back to software rendering, similar to how init_gpu_inner() in gpu_context.rs:132-148 already handles panics.

The camera module already uses LowPower preference (camera.rs), which may avoid the problematic AMD iGPU on hybrid systems - a similar approach for the main rendering path on Windows could help.