Investigation into unifying the playback backends (Linux/MPV, Android/ExoPlayer,
Windows/webview) onto one engine with hardware acceleration. Conclusion: video
cannot be unified onto a native engine; audio can.
The blocker is not mpv-specific. WebKitGTK, WebView2 and Android WebView each
draw into their own compositor surface, so a native video surface sits either
entirely above or entirely below the webview and cannot interleave with HTML.
GStreamer and libVLC fail identically. mpv would additionally regress streaming:
it has no adaptive bitrate, while the current hls.js path does.
Six specs added:
- playback-backend-unification: the analysis and decision, with evidence
- android-audio-settings-parity: set_audio_settings on ExoPlayerBackend
- android-native-video-spike: timeboxed test of SurfaceView compositing
- windows-native-audio-backend: replace the webview <audio> shim with libmpv
- libmpv2-migration: dead libmpv git pin -> libmpv2, plus a LICENSE file
- playback-docs-corrections: the requirement-status fixes applied here
Corrections to requirements.md, all verified against source:
- UR-031/DR-034 claimed crossfade was "Done (Linux only)". It is implemented
nowhere (mpv_backend.rs has a bare TODO) and is architecturally blocked on
mpv, whose single-stream audio chain cannot feed acrossfade's two inputs.
- Parity matrix listed crossfade as a Linux/Android gap; it is neither.
- The matrix omitted the equalizer, which has the same Linux-only shape.
- The suggested ConcatenatingMediaSource is deprecated in current Media3.
nativeAdapter.ts cited tauri#10152 as an upstream blocker for native Android
video. That issue is a stale feature request, dead since 2024-07-01; the
capability shipped in tauri 27d01834 (2024-09-02), and the related
black-screen bug was fixed in wry 0.39.4 (we ship 0.55.x). What is genuinely
unproven is SurfaceView-behind-WebView compositing, which the spike now tracks.
dtourolle
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