test0r
50e0c2b996
Two related fixes that surfaced during the first hantro-vpu (RK3568) smoke test of the multiplanar build: 1. **OUTPUT queue must be non-empty at STREAMON.** Hantro's vb2_start_streaming rejects an empty queue with EINVAL. Some VA-API callers (notably ffmpeg's vaapi-copy path) call vaCreateContext with num_render_targets=0 and allocate render targets lazily. The OUTPUT (bitstream-input) pool must NOT be sized off surfaces_count alone — it is a request-time resource, not per-surface. Quick fix: floor the pool to 4 buffers when the caller passes 0. (A proper decoupling of OUTPUT pool from surface lifecycle is documented in upstreamable_design.md.) 2. **Device-wide stateless H.264 controls before STREAMON.** The V4L2 stateless framework requires V4L2_CID_STATELESS_H264_ DECODE_MODE and START_CODE be set on the device fd (request_fd=-1) before stream start. Per-request controls (SPS/PPS/SLICE_PARAMS/etc.) attached to a request_fd come later via h264_set_controls(). hantro-vpu accepts only DECODE_MODE_FRAME_BASED; START_CODE_ANNEX_B matches what the existing slice-assembly path emits. This is set unconditionally for now (errors silently ignored) to keep cedrus and other backends compatible — they may default to SLICE_BASED and not expose DECODE_MODE at all. Probe-then-set via VIDIOC_QUERYCTRL is the upstream-correct approach (see upstreamable_design.md §3). After this patch, vainfo still enumerates as before, but the first mpv vaapi-copy attempt advances past STREAMON and into actual decode submission. Signed-off-by: Markus Fritsche <fritsche.markus@gmail.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.