claude-noether
f1be489c75
Sonnet Plan-agent review of phase1_pi5_hevc plan. Empirically verified each finding against current source per feedback_review_empirical_over_theoretical BEFORE accepting: F1 (CRITICAL): #ifdef __arm__ at image.c:239+268 kills NC12 (and already-present NV15) detile on AArch64. fresnel iter39 5/5 PASS masked this because 10-bit path was never exercised. Fix: extend guard to __aarch64__. F2 (CRITICAL): destination_bytesperlines for NC12 source returns column-stride (1080) not linear-NV12 Y stride (1280). VAImage consumers see wrong pitch. Fix: override in RequestCreateImage when src=NC12, dst image=NV12. F3 (CRITICAL): request.c primary-driver detection has else-if branches for rkvdec and hantro-vpu only. On higgs (rpi-hevc-dec primary), neither matches → new fd pair stays -1 → routing no-ops. Fix: add explicit rpi-hevc-dec branch. F4 (accepted): add 1366x768 fixture to exercise column padding. F5 (verify-only): HEVC START_CODE_ANNEX_B may not work on rpi-hevc-dec (kdirect uses NONE). Don't pre-gate; verify empirically in Phase 7. F6 (CRITICAL): iter25 synthetic-SPS pre-seed fires for HEVC regardless of driver_kind. Would issue HEVC_SPS to rpi-hevc-dec which doesn't need it AND uses different submission order. Fix: gate on driver_data->video_fd != video_fd_rpi_hevc_dec. F7/F8 (no findings): image.c gate predicate sound; cross-device regression scope clean. Amended Phase 6 step list with 3 new gating actions. Phase 7 verification expanded with empirical START_CODE check + 1366 fixture. Co-Authored-By: Claude Opus 4.7 <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.