claude-noether
27d82e3cf4
Three sites enabling VP8 profile recognition through the libva config
path:
1. RequestQueryConfigProfiles: NEW enumeration block probing
V4L2_PIX_FMT_VP8_FRAME against single + MPLANE OUTPUT formats.
Mirrors iter2 HEVC enumeration block. Surfaces VAProfileVP8
Version0_3 in vainfo on hantro env binding.
2. RequestCreateConfig: NEW case VAProfileVP8Version0_3 with
break — same shape as iter1 MPEG-2 + iter2 HEVCMain (no
profile-specific config validation in the libva backend;
validation deferred to vaCreateContext / control submission).
3. RequestQueryConfigEntrypoints: VAProfileVP8Version0_3 added to
the existing fall-through case list — surfaces VAEntrypointVLD.
After this commit alone, vainfo lists VP8Version0_3 (Phase 1
criterion 1) but vaCreateContext / runtime decode would fail at
later stages because no codec dispatcher exists yet (added in
commit B + C).
Refs:
../fresnel-fourier/phase4_iter3_plan.md (Commit A site list)
../fresnel-fourier/phase2_iter3_situation.md (B1, B2, B3
bug enumeration)
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.