claude-noether
229d6d11be
Fix-forward for commit C (3aab187): Phase 2 source-read missed a
third occurrence of #include <mpeg2-ctrls.h> in src/context.c:42.
The Phase 2 grep audit reported only two callsites
(src/config.c:37, src/mpeg2.c:38), both removed in commit B.
After commit C deleted include/mpeg2-ctrls.h from disk, the build
broke on context.c with:
../src/context.c:42:10: fatal error: mpeg2-ctrls.h:
No such file or directory
42 | #include <mpeg2-ctrls.h>
| ^~~~~~~~~~~~~~~
The include in context.c was vestigial — context.c references no
V4L2_CID_MPEG_VIDEO_MPEG2_* symbols and never needed the header
even before iter1's rewrite. The Phase 2 grep was simply incomplete.
This commit drops the orphan include line. Build now passes; install
clean; Phase 1 criterion 4 (DMA-BUF GL HW=SW byte-identical pixel
hashes) still PASS:
HW frame 1: 6e7873030dbf0403c67f35dd106ebef3c7909a0fd12433b82ad758e7fee9f092
SW frame 1: 6e7873030dbf0403c67f35dd106ebef3c7909a0fd12433b82ad758e7fee9f092
HW frame 2: ccc7ce08810d4a96e9ba7a19f4f95bbf6cc861bda9337604b5c668ad52bef7de
SW frame 2: ccc7ce08810d4a96e9ba7a19f4f95bbf6cc861bda9337604b5c668ad52bef7de
Per feedback_dev_process.md Phase 6 discipline:
"If a plan revision is needed mid-implementation, surface it
explicitly and re-enter Phase 4."
This is a 1-line scope expansion of commit B's "drop mpeg2-ctrls.h
include from all callsites" intent. Surfacing explicitly here
rather than silently amending B (which is already pushed). No
re-lock of plan needed; the spirit of File 1+2 in
phase4_iter1_plan.md was "drop the include from every file that
has it." The audit method (Phase 2 grep) was the gap.
Lesson for Phase 8 memory update: a more authoritative completeness
check than naive grep before deleting a header — recursive build
attempt to drive out hidden includes, or grep with no path filter
would have caught it.
Refs:
../fresnel-fourier/phase4_iter1_plan.md (File 3 + audit)
../fresnel-fourier/phase2_iter1_situation.md Bug 3 (incomplete
audit)
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.