claude-noether
4f6ba6c0e3
src/hevc-ctrls/v4l2-hevc-ext-controls.h (NEW, MIT, ~95 LOC):
Verbatim mirror of Linux 7.0 V4L2_CID_STATELESS_HEVC_EXT_SPS_ST_RPS
and _LT_RPS control IDs + struct definitions + flag macros. Each
symbol is ifndef-guarded so when ampere's linux-api-headers
eventually bumps to 7.0+, the kernel header takes precedence and
this shim silently no-ops. Citation block links the upstream
Casanova v8 series.
Per LGPL section 3.b, kernel UAPI struct definitions are excepted
from GPL inheritance, so copying them into MIT userspace is fine.
src/request.h: added has_hevc_ext_sps_rps_rkvdec + _hantro bool
fields on struct request_data — pair-of-flags layout mirrors
video_fd_rkvdec / video_fd_hantro (iter38 multi-device-probe
pattern, per feedback_multi_device_probe_design). Phase 5 review
identified single-scalar storage as a silent-misbehavior risk
across device-switch boundaries.
src/request.c:
- new probe_hevc_ext_sps_rps_controls(fd) helper: queries the two
new CIDs via VIDIOC_QUERYCTRL; returns true iff both register.
RK3399 rkvdec (linux 6.x or 7.x without VDPU381/383 bindings)
returns false; RK3588 rkvdec (VDPU381/383) returns true.
- probe each driver_data->video_fd_rkvdec / _hantro after the
iter38 multi-device-probe block at VA_DRIVER_INIT time
- log-line if rkvdec supports it - diagnostic for Phase 7
src/meson.build: added the new UAPI header to the headers list.
Build verified: ninja -C build clean, .so produced. The new probe
runs at driver init and stores the result, but nothing CONSUMES the
result yet — that's Step 4 (h265_set_controls wiring).
Per ampere-kernel-decoders campaign iter2 Phase 4 step 3 (amended
by Phase 5 review item 'per-fd storage').
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.