claude-noether
3ffa9d0d17
Phase 6 implementation. Backend builds clean on higgs (Debian 13 trixie, aarch64), vainfo lists VAProfileHEVCMain via rpi-hevc-dec, multi-device probe finds /dev/video19 + /dev/media1, CreateContext + S_FMT + REQBUFS + STREAMON all succeed. Phase 7 partial: infrastructure works, 10 frames flow through the pipeline (correct byte counts produced — 13824000 for 1280x720 x 10 NV12 frames). But every DQBUF CAPTURE returns V4L2_BUF_FLAG_ERROR so output content is wrong (libva sha != kdirect sha). The decode itself is failing on the rpi-hevc-dec side despite all ctrl submissions returning success. Code changes: - request.h: video_fd_rpi_hevc_dec / media_fd_rpi_hevc_dec slots + has_hevc_ext_sps_rps_rpi_hevc_dec flag (mirrors iter38 + iter2 pair-of-flags pattern, naturally false on Pi). - request.c: known_decoder_drivers gains rpi-hevc-dec; primary-driver probe gets an else-if branch setting the new fds (Phase 5 F3); request_switch_device_for_profile prefers 'p' for HEVC when rpi-hevc-dec present. - context.c: per-fd want_pixfmt (NC12 on Pi), capture_pixelformat taken from video_format slot (not hardcoded NV12/NV15); synthetic-SPS pre-seed gated off for Pi (Phase 5 F6); destination_sizes uses nv12_col128_uv_plane_offset for NC12 SAND layout (Phase 5 F2); per-driver HEVC_START_CODE (NONE on Pi, ANNEX_B on RK); per-driver context_object->h264_start_code (skip prepend on Pi). - video.c: NV12_COL128 video_format entry (8-bit SAND, single buffer, 2 planes, NV12 drm_format with MOD_NONE so detile branch fires rather than tiled_to_planar). - nv12_col128.c/.h: detile primitive (Y + UV per-plane, kernel hevc_d_video.c bytesperline formula + ffmpeg/Kynesim per-pixel offset). UV plane offset = 128 * ALIGN(h, 8) — within-column (SAND interleaves Y+UV per column, NOT plane-concatenated; earlier wrong formula caught by Phase 7 SEGV). - image.c: #ifdef __arm__ extended to __arm__ || __aarch64__ (Phase 5 F1 — guard was killing detile path on all aarch64 hosts including fresnel iter39 NV15 path, masked because 10-bit never exercised); RequestCreateImage NC12 → NV12 stride override (linear width, not column-stride); copy_surface_to_image NC12 detile branch (gates on fourcc + v4l2_format). - nv15.h: fallback V4L2_PIX_FMT_NV15 define (Debian 13 headers omit it though they have NC12). - nv12_col128.h: fallback V4L2_PIX_FMT_NV12_COL128 + V4L2_PIX_FMT_NV12_10_COL128 (Arch / mainline pre-Pi headers). - tests/test_nv12_col128_detile.c: hand-crafted-bytes unit test; passes (8 cases: Y + UV for 4 widths incl. 1366 misaligned; UV-offset helper). - meson.build / nv12_col128 sources listed. Phase 7 status: not yet bit-exact. Remaining diagnosis: per-frame S_EXT_CTRLS payload diff vs kdirect (kdirect sends 4 ctrls SPS+PPS+decode_params+slice_array; ours sends 5 incl. scaling_matrix; field ordering differs). Likely the slice_array contents need per-driver handling for rpi-hevc-dec's expected layout. Beyond in-session reach. iter38 5/5 baseline on fresnel + ampere should be unaffected (new fd stays -1 on non-Pi hosts; all gates either short-circuit on fd-not-present or no-op). 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.