claude-noether
f61f736380
Fixes the rkvdec_hevc_prepare_hw_st_rps out-of-bounds kernel OOPS that blocked HEVC decode on ampere (RK3588) per marfrit/libva-v4l2-request-fourier#3 and ampere-fourier iter1 close. Mechanism (Phase 5 amendment to issue body): The new EXT_SPS controls are registered as V4L2_CTRL_FLAG_DYNAMIC_ARRAY in vdpu38x_hevc_ctrl_descs (rkvdec.c:279/284) with cfg.dims = { 65 }. The v4l2-ctrl framework init-allocates 1 zeroed element (ctrls-core.c:2116). When num_short_term_ref_pic_sets > 1, rkvdec_hevc_prepare_hw_st_rps (rkvdec-hevc-common.c:393-405) iterates idx 0..N-1 and overruns the 1-element kernel allocation. Submitting an N-element dynamic-array control via S_EXT_CTRLS extends the framework allocation. Userspace fix: - VIDIOC_QUERY_EXT_CTRL probe at first HEVC CreateContext sets driver_data->has_ext_sps_rps (true on VDPU381/383, false on legacy RK3399 — control unregistered there, so fresnel iter38 5/5 + iter39 sub-profile paths are byte-identical to pre-iter2). - When set, h265_set_controls appends EXT_SPS_ST_RPS + _LT_RPS as calloc'd zero arrays, sized by VAAPI's count fields and capped at H.265 §7.4.3.2 spec maxima (ST 64, LT 32). Min 1 (kernel rejects 0). - Free post-S_EXT_CTRLS. Decode correctness scope: VAAPI does NOT expose per-set st_ref_pic_set syntax elements (delta_idx_minus1, delta_rps_sign, etc.) — confirmed in va_dec_hevc.h. All-zero entries give empty inter-pred RPS per set, which is correct for IDR-only streams and incorrect for streams with inter-pred RPS dependence. iter2 acceptance: stop the OOPS. Decode-correctness for inter-RPS content is a known follow-up requiring either bitstream-snoop or SPS-passthrough via a new VAAPI extension. Files: - include/hevc-ctrls.h: #ifndef-guarded fallback definitions for V4L2_CID_STATELESS_HEVC_EXT_SPS_{ST,LT}_RPS + structs (ampere host is on linux-api-headers 6.19-1; the new CIDs land in 7.0). - src/request.h: driver_data->has_ext_sps_rps (persists for driver lifetime; gated solely by HEVC code path so cross-codec leakage impossible). - src/context.c: probe at HEVC CreateContext via v4l2_query_ext_ctrl. - src/h265.c: controls[5] → controls[7]; #include <hevc-ctrls.h> (replaces <linux/v4l2-controls.h>) for forward UAPI compatibility. Compile-tested on boltzmann (aarch64 native, gcc 15.2.1): clean .so, 0 new warnings. Fresnel cross-device safety: legacy RK3399 rkvdec_ctrl table omits the CIDs; probe returns false; new code path never executes. iter39 sub-profile work (commits662f887+8746690) is preserved in-tree; iter2 is a forward-compatible additive change. Refs: marfrit/libva-v4l2-request-fourier#3 ampere-fourier/iter1_close.md HEVC blocker ampere-fourier/iter2_phase0_findings.md 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.