bugfix: hardware decoder issue in certain files, added support to swi…

[anilabhadatta]

Edited player_bridge.cpp
Edited player_bridge.cpp
Viewed controls.html:1-23

Here is the updated Pull Request description that properly explains the codec and hardware decoder logic:

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Summary

Fixed playback black screens on Windows by correcting the decoderPriority UI-to-native mapping and resolving a critical hardware decoder codec compatibility issue by switching from forced D3D11VA to smart auto-probing.

PR type

• Reproducible bug fix
• UI glitch/bug fix
• Behavior bug/regression fix
• Small maintenance only, with no UI or behavior change
• Docs accuracy fix
• Translation/localization only
• Approved larger or directional change

Why

We discovered two major issues causing black screens and playback failures on Windows:

1. Hardware Decoder Compatibility (The Core Issue): Previously, the player was hardcoded to use hwdec=d3d11va (forcing the AMD GPU's Direct Rendering path). However, different GPUs support different codec profiles. For example, when playing a VC-1 or unsupported Dolby Vision stream, forcing the AMD decoder resulted in silent failures and black screens. By changing the base configuration to hwdec=auto, MPV is now allowed to intelligently probe the system's capabilities at runtime. On dual-GPU systems (e.g., AMD + NVIDIA), auto correctly discovers which GPU can actually handle the specific codec (e.g., selecting nvdec-copy via NVIDIA CUDA for VC-1) instead of forcing a crash on the AMD card.
2. Decoder Priority Mapping Offset: The UI settings send integer priorities (0: Device Only, 1: Prefer Device, 2: App Decoders/CPU), but the C++ bridge was checking for 1, 2, and 3. This meant user selections were completely ignored, falling through to broken base cases.

Desktop scope

Windows only (composeApp/src/desktopMain/native/windows/player_bridge.cpp).

Issue or approval

No linked issue - fixes direct playback crash/black screen regression on Windows native player.

UI / behavior impact

• No UI change
• No behavior change
• UI changed only to fix a documented glitch/bug
• Behavior changed only to fix a documented bug/regression
• UI change has explicit maintainer approval
• Behavior change has explicit maintainer approval

Policy check

• I have read and understood CONTRIBUTING.md.
• This PR is small, focused, and limited to one problem.
• This PR is scoped to the desktop app, desktop packaging, desktop documentation, or shared code required for desktop behavior.
• This PR is not cosmetic-only.
• Any UI change fixes a linked glitch/bug and includes visual proof, or this PR has no UI change.
• Any behavior change fixes a linked bug/regression or has explicit approval, or this PR has no behavior change.
• This PR does not bundle unrelated refactors, cleanups, formatting, or drive-by changes.
• This PR does not add dependencies, architecture changes, migrations, or product-direction changes without explicit approval.
• I listed the testing performed below.

Scope boundaries

This fix does not change the UI text or alter how the Kotlin UI handles its state. It strictly aligns the C++ backend to receive the correct state and lets the MPV engine perform native codec probing.

Testing

Tested on Windows with a multi-GPU setup (AMD + NVIDIA) using various codecs (including VC-1 and HEVC).

• Auto-probing success: Verified that decoderPriority == 0 (Device Only) runs hwdec=auto. Log outputs proved that MPV successfully tests and selects the optimal decoder (nvdec-copy on NVIDIA) when the AMD direct path fails.
• CPU Fallback: Verified decoderPriority == 1 (Prefer Device) correctly applies vd-lavc-software-fallback=yes alongside auto, providing a safety net if no GPU supports the codec.
• Pure Software: Verified decoderPriority == 2 (App Decoders) runs hwdec=no to force software decoding for absolute stability.

Screenshots / Video

Before:

After:

Breaking changes

None.

Linked issues

26

Note to Author:

Please do check if the code changes are as expected, and hopefully, it should not break in any scenario. If I am missing anything, do let me know.
I have done the changes only for the Windows OS,

Current System Specs
AMD Ryzen 6800HS
32GB DDR5
NVIDIA RTX 3080 8GB Laptop Variant