forked from unom/punktfunk
enricobuehlerandClaude Fable 5
f4c3a5d0c3
Live-diagnosed on the RTX box during the adaptive-bitrate A/B: 2 of 3 streams died with VK_ERROR_DEVICE_LOST at stream start or at a mid-stream encoder rebuild, then zombied — the demote-to-software path rebuilt the decoder against the same dead device, FFmpeg wedged inside the rebuild, and the pump flushed a never-draining backlog every 2 s forever. No OS TDR: the client's own Vulkan misuse. Two causes: 1. The presenter creates ONE graphics-family queue and hands FFmpeg's AVVulkanDeviceContext the same family (nb_graphics_queues=1 ⇒ queue 0) for its transfer/compute prep — so the pump thread and the presenter thread submitted to the SAME VkQueue with no shared lock, violating vkQueueSubmit's external-sync rule exactly when FFmpeg puts work on the graphics queue (decoder open / frames-context rebuild = stream start and every ABR encoder re-target). New guard-less QueueLock (FFmpeg's lock_queue/unlock_queue callbacks are a raw pair) shared by all four queue users: FFmpeg (callbacks installed via user_opaque), the presenter's submit/present/wait-idle, and the Skia overlay's flushes. 2. Swapchain recreation destroyed the old swapchain + render semaphores after ONE fence cycle — the fence proves our submit, not the presentation engine's semaphore consumption (VUID-vkDestroySemaphore-05149 + VUID-vkDestroySwapchainKHR-01282 on every recreate). Recreate now drains the queue (vkQueueWaitIdle under the shared lock — safe now that FFmpeg honours it) and destroys immediately; the deferred DisplayGarbage machinery is gone. Resilience: VK_ERROR_DEVICE_LOST anywhere in a present error chain is now fatal — the run loop fails the session loudly instead of demoting to software on a dead device (the zombie path). Verified on the RTX box (RTX 4090 → host .21) under VK_LAYER_KHRONOS_validation: 3/3 stream start/stop cycles clean, then 8 mid-stream encoder rebuilds in one session (4 ABR down-steps under 10% induced loss + 4 clean-link recovery up-steps — the exact scenarios that previously killed the device): 0 device losses, 0 wedges, both recreate VUIDs gone (previously fired on every path). Remaining validation messages are FFmpeg's own video-session VUIDs, untouched by this change. Linux: clippy -D warnings + tests green (home-worker-2). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>