claude-noether
bed75c0cef
RK3588 has THREE hantro-vpu instances (legacy MPEG2/VP8 at /dev/video2,
encoder at /dev/video3, vpu981 AV1 at /dev/video4). The existing
2-device probe is "RK3399-shaped knowledge" — silently picks the first
hantro-vpu and never finds vpu981.
This commit adds:
- video_fd_vpu981 + media_fd_vpu981 slots to request_data
- video_node_supports_output_fmt(): capability probe via VIDIOC_ENUM_FMT
on OUTPUT/OUTPUT_MPLANE queues
- find_decoder_device_by_driver_with_fmt(): walks /dev/media* matching
driver name AND capability filter (V4L2_PIX_FMT_AV1_FRAME for vpu981)
- 'a' kind in request_device_kind_for_profile (VAProfileAV1Profile0)
- 'a' branch in request_switch_device_for_profile
- vpu981 probe at backend init, alongside existing rkvdec + hantro
- vpu981 fd cleanup in RequestTerminate
- VAProfileAV1Profile0 → V4L2_PIX_FMT_AV1_FRAME in codec.c
Verified on ampere:
$ LIBVA_DRIVER_NAME=v4l2_request ffmpeg ... 2>&1 | grep iter38
v4l2-request: auto-selected codec device: /dev/video1 + /dev/media0
v4l2-request: iter38: also opened hantro-vpu decoder at /dev/video2 + /dev/media1
v4l2-request: ampere-av1: vpu981 AV1 decoder at /dev/video4 + /dev/media3
Three devices opened. HEVC still works (iter2 EXT_SPS_RPS probe still
triggers on rkvdec, sibling-campaign bit-perfect behaviour preserved).
Next steps: config.c advertise VAProfileAV1Profile0, surface.h add
av1 substruct, picture.c dispatch, av1.{c,h} for the codec dispatch
(~700 LoC mirroring Kwiboo v4l2_request_av1.c).
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.