fix(mediaplayer): submit the Android Vulkan resolve from a plugin-owned command buffer

[towneh]

Summary

Fixes #922 — media player video crashed the client on Quest within about a second of the first decoded frame: a null-pointer dereference inside the Adreno driver's vkCmdExecuteCommands, on Unity's Vulkan submission thread. On-device isolation (detailed in the issue) pinned the trigger to the commands the present path recorded into Unity's command buffer via CommandRecordingState — a pipeline barrier plus the plugin's own render pass and draw. Declaring an outside-render-pass precondition didn't help; skipping the recorded work entirely removed the crash.

The present path no longer touches Unity's command buffers at all:

• The YCbCr→RGBA resolve records into a plugin-owned command buffer (one per import-ring slot, one shared pool) and is submitted on the graphics queue directly from the render event, which is now configured with kUnityVulkanGraphicsQueueAccess_Allow — Unity holds its own queue users off the queue while the callback runs.
• A fence per slot replaces Unity's safeFrameNumber for reclaiming imported AHardwareBuffers; release waits in-flight fences (capped) before destroying.
• The Unity RenderTexture's VkImage is queried with AccessTexture(ObserveOnly) — no barriers recorded on the plugin's behalf. No layout coordination with Unity is needed: the resolve render pass already takes the attachment from UNDEFINED (contents discarded — every draw overwrites the full frame) and returns it in SHADER_READ_ONLY, the layout Unity samples it in. Same-queue submission order plus the pass's external dependencies order the write against Unity's sampling.
• basis_gfx_vk_begin_record (the Unity command-buffer access) is removed.

Rebuilt libbasis_media_native.so (arm64-v8a, NDK r27c) is included.

Stacked on #921 — this branch is based on the multichannel-audio branch, so the diff shows #921's commits until that merges; the change to review here is the final commit (fix(mediaplayer): submit the Android Vulkan resolve from a plugin-owned command buffer).

Required checks

All boxes below must be ticked before this PR can merge. If a check is genuinely N/A, tick it anyway and explain under Notes.

• Tested — I built and ran this locally. The change works in the editor and (where relevant) in a built player.
• Transform access is combined and limited — In hot paths, transform reads/writes go through TransformAccessArray or are otherwise batched. I have not added per-frame transform.position / transform.rotation / transform.localPosition calls inside loops. Whenever I need both position and rotation, I use the combined APIs — SetPositionAndRotation / SetLocalPositionAndRotation for writes, GetPositionAndRotation / GetLocalPositionAndRotation for reads — instead of two separate property accesses; the combined call does one local-to-world matrix traversal instead of two.
• Addressables used for asset/memory loading — Any new asset loads go through Addressables. No new Resources.Load, no direct asset references that pull large content into memory on scene load.
• No new GetComponent / AddComponent where avoidable — Where unavoidable, the result is cached on a field, and any GetComponent<T> is replaced with TryGetComponent<T>(out var x) — bare GetComponent will be denied. TryGetComponent is the modern API (Unity 2019.2+) and skips the Editor-only GC allocation GetComponent causes when a component is missing: Unity wraps the null return in a managed "fake null" object so its overloaded == operator can still detect destroyed C++ objects, and constructing that wrapper allocates; TryGetComponent returns a bool plus out parameter and never builds the wrapper. None of these calls run inside Update, LateUpdate, FixedUpdate, jobs, or other per-frame code paths.
• Per-frame work is scheduled through BasisEventDriver — Any new per-frame work hooks into BasisEventDriver rather than adding standalone Update / LateUpdate / FixedUpdate callbacks on a MonoBehaviour.
• Anything added to BasisEventDriver is bulletproof, or guarded by try/catch — BasisEventDriver runs the single per-frame tick that drives the whole framework (network apply, local player sim, blendshapes, JigglePhysics, nameplates, and more) as one sequential chain. An unhandled exception anywhere in that chain aborts the rest of the tick, so every step after the throwing one is silently skipped for that frame. New work added to the driver must either be guaranteed not to throw, or be wrapped in a try/catch that contains the failure and surfaces it through BasisDebug — logged once / rate-limited, never every frame (see the existing HVRBasisBuiltInAddresses.Simulate() guard for the pattern). Expect this to be scrutinized closely in review.
• Considered jobification — I asked whether this work can be moved to a Unity Job (Burst-compiled where possible). If it can, it is. If it cannot, the reason is in Notes.
• No needless { get; set; } properties or access lockdowns — Public fields are fine; Basis is meant to be read and modified freely, so don't wall things off private/internal without a real reason. Don't wrap a field in { get; set; } when the accessors do nothing — property accessors have a real performance cost vs direct field access, and the lead maintainer prefers plain fields (or a method / setter-only property when only the setter needs logic) over a noop-getter pair. For .Instance singletons, callers reassigning Type.Instance is allowed; if that would break your code, log a warning or throw — don't block the assignment. Locking down access is not your call.
• Camera access goes through BasisLocalCameraDriver — Code that needs the local camera (transform, projection, rig data, etc.) pulls it from BasisLocalCameraDriver rather than looking one up itself. Don't roll a separate camera discovery path.
• Logging uses BasisDebug — All new logging calls go through BasisDebug.Log / BasisDebug.LogWarning / BasisDebug.LogError (with an appropriate LogTag) instead of UnityEngine.Debug.Log / Debug.LogWarning / Debug.LogError. BasisDebug routes through Basis's tagged, color-coded logger and respects the project-wide LoggingDisabled toggle so logging can be killed at runtime; bare Debug.Log calls bypass that and will be denied.
• No scene-wide discovery for dependencies — New code is architected so it does not need FindObjectOfType / FindObjectsOfType / GameObject.Find / FindGameObjectsWithTag to locate what it depends on. References are wired in — registered through an existing manager/driver, injected at init, or passed in by the caller — rather than discovered by scanning the scene at runtime. If a scene scan is genuinely unavoidable, justify it under Notes.
• No allocations in hot paths — Per-frame code (Update / LateUpdate / FixedUpdate, simulation loops, jobs, anything called once per frame or more) does not allocate. No new on reference types, no LINQ, no string concatenation/interpolation, no boxing, no foreach over interface-typed collections. Allocate once at init and reuse the buffer.
• No debugging in hot paths — No log calls of any kind on per-frame paths, including BasisDebug. Hot-path logging floods the console and incurs cost on every frame regardless of whether the message is filtered out downstream. If a hot-path log is needed while iterating, gate it behind #if UNITY_EDITOR and remove (or leave gated) before merge.
• Hot-path collection access is optimized — Cache .Count (lists) / .Length (arrays) into a local int before the loop instead of re-reading the property each iteration. Prefer T[] (with a separate length int when the array is over-sized) over List<T> where the data is hot — Unity's mono BCL doesn't expose CollectionsMarshal.AsSpan(List<T>), so a list can't be fed into Span<T> / unsafe paths cleanly. Where the perf justifies it, drop into Span<T> / ref locals / Unsafe.As / unsafe pointer code to skip bounds checks and copies, and call out the invariants you're relying on under Notes so reviewers can sanity-check them.

Testing details

Tick the platforms you actually tested on. Leave the rest unticked — these are informational and do not block merge.

• Windows
• Linux
• Android
• iOS
• macOS

Input / control mode coverage:

• Tested in VR (note headset under Notes)
• Tested in desktop / non-VR mode
• Tested with phone controls (mobile touch input)
• N/A — change does not touch player/XR/input code

Where applicable, confirm these flows still work after your changes:

• Hot-switching (desktop ↔ VR mode swap at runtime)
• Avatar swapping
• Server swapping (joining / leaving / changing servers)
• N/A — change does not touch any of the above

Notes

Scope / N/A checks: entirely a native C/C++ plugin change (Native~/android, Native~/unity, one internal header) plus the rebuilt arm64 .so — no C# is touched, so the Unity-side checks (transform access, Addressables, GetComponent, BasisEventDriver, properties, camera driver, BasisDebug, scene discovery, hot-path allocations/collections) have nothing to apply to. Jobification: N/A, native present path.

Tested on Quest Pro (Android 14), sideloaded build, H.264 + AAC over RTSP/TCP:

• Where the previous build crashed within ~1 second of the first decoded frame (identical tombstone across multiple runs — see Media player: video crashes on Quest (Adreno null-deref in vkCmdExecuteCommands from the Vulkan present path) #922), this build played through repeated runs and a multi-minute soak on a single process, including stream close and reload.
• Video output was verified against a reference frame extracted from the source file: colours (including the chroma-sensitive magenta/cyan bars), greyscale and orientation all match ground truth.
• 5.1 audio alongside video unaffected (as validated in fix(mediaplayer): decode discrete multichannel AAC on Android #921).

Trade-offs / caveats:

• The submit happens on the graphics queue once per decoded frame from the render event. GraphicsQueueAccess_Allow means Unity briefly holds its queue users off the queue during the callback; no frame-pacing impact was observed in the soak, but it's the structural cost of not sharing Unity's command buffers.
• Windows is untouched (the D3D11/D3D12 present path is separate; the Vulkan glue changes compile only on Android).