test0r
c45fea96e3
Compound patch carrying the fork's pre-Step-1 substrate, originally authored by Jernej Škrabec / fourier on top of bootlin'sa3c2476: - src/h264.c + src/picture.c: V4L2_CID_MPEG_VIDEO_H264_* renamed to V4L2_CID_STATELESS_H264_*, struct shapes tracked to mainline (V4L2_CID_STATELESS_H264_DECODE_MODE/_START_CODE added to the passthrough shim). - include/hevc-ctrls.h: redirect shim to <linux/v4l2-controls.h> (kernel-side HEVC controls now live in the canonical UAPI header). - src/meson.build: src/h265.c / src/h265.h commented out — HEVC build path is excluded from this fork (RK3568 hantro G1/G2 has no HEVC, and the kernel-side HEVC controls have a separate rework in flight upstream). - src/tiled_yuv.S: aarch64 stub for tiled_to_planar (assembly source was sunxi-cedrus armv7-only; aarch64 needs a stub to keep the build linking). - include/h264-ctrls.h: removed (dead post-fourier — no source includes it; the passthrough shim's CID aliases live in the kernel header now). Functionally equivalent to the prior fork master commits:c1f5108V4L2_PIX_FMT_H264_SLICE rename4ccbfe9Strip HEVC build pathda9f2a5include/h264-ctrls.h passthrough + CID aliasesfc4bb10src/h264.c track upstream UAPI shape13e9b64src/h264.c drop num_slices field4d14ffbsrc/tiled_yuv.S aarch64 stub1b02c9bsrc/h264.c include utils.h Folded into one commit during 2026-05-04 Step 1 reconciliation (see ../phase0_evidence/2026-05-04/findings.md). Per-patch history of the early fork commits preserved on the pre-step1 branch. 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.