claude-noether
a09c03c154
iter4 (385dee1) replaced the original media_request_reinit pattern with close+media_request_alloc per frame to escape an EINVAL on S_EXT_CTRLS that turned out to be a DPB-payload bug (74d8dd1, FFmpeg V4L2_H264_FRAME_REF semantics). The per-frame close+alloc model worked for mpv vaapi-copy (single-surface recycle) but raced under Firefox 150's MediaSource pipeline (multi-surface rotation): fd=30 got reused via lowest-free-fd allocation faster than the kernel- side per-buffer state-machine could tear down the prior request, producing intermittent VIDIOC_QBUF EINVAL on OUTPUT after 1..53 successful frames. Phase 2 telemetry confirmed: - DQBUF returned the index we passed (no FIFO mismatch) - SPS/PPS/DECODE_PARAMS/SCALING_MATRIX byte-identical between mpv and Firefox first 64 bytes - Pool size bump 4 -> 16 only delayed the failure (62 frames) - Different OUTPUT slot indices failed across runs (race signature) Fix: each OUTPUT pool slot owns a permanent request_fd allocated once at request_pool_init and REINIT'd between uses in RequestSyncSurface. 1:1 slot-to-fd binding eliminates cross-slot fd reuse entirely. Pool stays driver-wide (multi-context safe per iter5 Track E); slots cycle through 16 distinct fds in round-robin acquire. Files: - request_pool.h: add request_fd field to slot struct; init signature takes media_fd - request_pool.c: alloc per-slot fd at init, close at destroy - context.c: pass driver_data->media_fd; pool size 4 -> 16 - picture.c: BeginPicture binds slot->request_fd to surface; EndPicture's per-frame media_request_alloc removed - surface.c: RequestSyncSurface uses media_request_reinit instead of close+alloc; DestroySurfaces close removed (slot owns fd); error path close removed; surface_object NULL-init for the -Wmaybe-uninitialized warning fix Empirical verification (clean build sha ebe396d5..., no diagnostic instrumentation): - Firefox 150 + bbb_1080p30_h264.mp4 + LIBVA_DRIVER_NAME=v4l2_request + sandbox enabled: 35s+ playback, zero "Unable to queue buffer" / "Unable to set control(s)", lsof shows RDD process holds /dev/video1 + /dev/media0 throughout. Driver stderr: only the single cap_pool_init: 24 slots ready line. - mpv vaapi-copy 50 frames: zero errors, "Using hardware decoding (vaapi-copy)" - no regression vs iter5-end driver. Pool-size bump diagnostic (Phase 5 sonnet design review feedback): 4 -> 16 alone took 1->62 frames, far short of the 30s success criterion (~900 frames at 30fps). REINIT discipline is the actual fix; pool 16 is comfortable headroom over typical H.264 MaxDpbFrames. Phase 5 sonnet code review: APPROVE-WITH-CHANGES (one comment attribution corrected: cleanup runs at RequestTerminate, not RequestDestroyContext, since the pool is driver-wide). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
v4l2-request libVA Backend
About
This libVA backend is designed to work with the Linux Video4Linux2 Request API that is used by a number of video codecs drivers, including the Video Engine found in most Allwinner SoCs.
Status
The v4l2-request libVA backend currently supports the following formats:
- MPEG2 (Simple and Main profiles)
- H264 (Baseline, Main and High profiles)
- H265 (Main profile)
Instructions
In order to use this libVA backend, the v4l2_request driver has to
be specified through the LIBVA_DRIVER_NAME environment variable, as
such:
export LIBVA_DRIVER_NAME=v4l2_request
A media player that supports VAAPI (such as VLC) can then be used to decode a video in a supported format:
vlc path/to/video.mpg
Sample media files can be obtained from:
http://samplemedia.linaro.org/MPEG2/
http://samplemedia.linaro.org/MPEG4/SVT/
Technical Notes
Surface
A Surface is an internal data structure never handled by the VA's user containing the output of a rendering. Usualy, a bunch of surfaces are created at the begining of decoding and they are then used alternatively. When created, a surface is assigned a corresponding v4l capture buffer and it is kept until the end of decoding. Syncing a surface waits for the v4l buffer to be available and then dequeue it.
Note: since a Surface is kept private from the VA's user, it can ask to directly render a Surface on screen in an X Drawable. Some kind of implementation is available in PutSurface but this is only for development purpose.
Context
A Context is a global data structure used for rendering a video of a certain format. When a context is created, input buffers are created and v4l's output (which is the compressed data input queue, since capture is the real output) format is set.
Picture
A Picture is an encoded input frame made of several buffers. A single input can contain slice data, headers and IQ matrix. Each Picture is assigned a request ID when created and each corresponding buffer might be turned into a v4l buffers or extended control when rendered. Finally they are submitted to kernel space when reaching EndPicture.
The real rendering is done in EndPicture instead of RenderPicture because the v4l2 driver expects to have the full corresponding extended control when a buffer is queued and we don't know in which order the different RenderPicture will be called.
Image
An Image is a standard data structure containing rendered frames in a usable pixel format. Here we only use NV12 buffers which are converted from sunxi's proprietary tiled pixel format with tiled_yuv when deriving an Image from a Surface.