marfrit
a7d585eee8
ffmpeg -hwaccel vaapi → libva-v4l2-request-fourier → /dev/video0 → daedalus_v4l2 kernel → REQ_DECODE on the chardev → daemon FFmpeg decode → byte-exact NV12 (FNV-1a 0x1eb34bfe, same hash the standalone test_m2m_stream produces for the same 128x96 VP9 keyframe). The pixel-correct decode through the libva path is the milestone. What's NOT yet working: libva times out on the media_request fd because buf_request_complete never fires (vb->req_obj.req is NULL when buf_done runs — the S_EXT_CTRLS EINVAL leaves the buffer un-bound to the request even though the buffer queues anyway). Phase 8.13 fixes the EINVAL so the request bind takes and the completion signal propagates. Kernel V4L2 request API integration: - media_device_ops.req_validate / req_queue = vb2_request_ validate / v4l2_m2m_request_queue (Phase 8.11) — MEDIA_IOC_REQUEST_ALLOC succeeds. - vb2_queue.supports_requests = true on OUTPUT queue — without this v4l2-core rejects S_EXT_CTRLS(REQUEST_VAL). - vb2_ops.buf_request_complete = daedalus_buf_request_complete → v4l2_ctrl_request_complete(req, &ctx->hdl). Without this v4l2-core WARNs at videobuf2-v4l2.c:440. - vb2_ops.buf_out_validate: sets field=V4L2_FIELD_NONE on OUTPUT buf. Required for the same WARN check. - requires_requests intentionally NOT set: lets the existing test_m2m_stream (direct QBUF, no request) keep working alongside the libva path. Stateless control re-registration: - Switched from v4l2_ctrl_new_std_compound(NULL p_def) to v4l2_ctrl_new_custom(&cfg, NULL) — pattern rkvdec / cedrus / hantro use. v4l2-core auto-fills elem_size + type from std table (verified: VP9_FRAME elem_size=168, matches sizeof(struct v4l2_ctrl_vp9_frame)). - No-op s_ctrl callback so SET requests don't crash — daemon ignores values, FFmpeg re-parses the bitstream. Verification on hertz (Pi 5, 6.12.75+rpt-rpi-2712): ffmpeg -hwaccel vaapi -i vp9_small.ivf … daemon: REQ_DECODE cookie=1 codec=1 bitstream=1566 bytes capture=128x96 1 planes daemon: decoder: opened vp9 context daemon: decoder: OK 128x96 fmt=0 (yuv420p) fnv1a=0x1eb34bfe … Same FNV-1a hash as the standalone test_m2m_stream produces for the same VP9 keyframe. End-to-end through libva. Remaining (Phase 8.13): - S_EXT_CTRLS EINVAL on V4L2_CID_STATELESS_VP9_FRAME despite matching elem_size — needs deeper validate-path debugging. - Once the request bind takes, buf_request_complete fires on buf_done, request fd signals completion, libva DQBUFs the decoded NV12. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
daedalus-v4l2
V4L2 stateless decoder for the Raspberry Pi 5 / CM5, backed by the
daedalus-fourier kernel library (VP9 + AV1 CDEF + H.264 video
decode kernels on VideoCore VII compute + ARM NEON).
Status: scaffold (2026-05-18). Architecture locked per daedalus-fourier session memory; implementation not yet begun.
What this is
Sibling repo to daedalus-fourier (the kernel library; cycles 1-9 closed).
A two-piece userspace + kernel-module stack that exposes a V4L2
stateless decoder interface (/dev/videoNN) so that
libva-v4l2-request-fourier → firefox-fourier /
chromium-fourier can drive it the same way they drive existing
hardware-decode pipelines on Pi 5 / RK3588.
+-----------------------------------------------------------+
| firefox-fourier / chromium-fourier (existing) |
+-----------------------------------------------------------+
| VA-API |
+-----------------------------------------------------------+
| libva-v4l2-request-fourier (existing, sibling project) |
+-----------------------------------------------------------+
| V4L2 stateless ioctl uAPI |
+-----------------------------------------------------------+
| daedalus-v4l2 kernel module (`kernel/`) |
| - registers /dev/videoNN |
| - parses V4L2 stateless ioctls (VP9/AV1/H.264 controls) |
| - forwards bitstream + controls to userspace daemon |
| via chardev or netlink |
+-----------------------------------------------------------+
| daedalus-v4l2 userspace daemon (`daemon/`) |
| - takes bitstream blobs + per-slice controls |
| - drives FFmpeg parsers via dlopen (Option γ) |
| - dispatches per-block ops via daedalus-fourier |
| public API (daedalus_dispatch_*) |
| - posts decoded frames back to kernel module |
+-----------------------------------------------------------+
| daedalus-fourier kernel library (sibling project) |
| - exports include/daedalus.h public API |
| - per-kernel CPU NEON + opportunistic V3D QPU dispatch |
| - 9 closed cycles across VP9, AV1 CDEF, H.264 |
+-----------------------------------------------------------+
| V3D 7.1 (Mesa userspace v3dv) + ARM NEON (BCM2712) |
+-----------------------------------------------------------+
Why this architecture (Option B + γ + sibling)
Locked by user 2026-05-18 from 3 options in
daedalus-fourier/docs/phase8_scoping.md:
- Option B over A (userspace v4l2loopback): real
/dev/videoNN, proper DRM PRIME / dmabuf for browser zero-copy. - Option γ: dlopen FFmpeg as parser at runtime. No vendoring, fastest to v1.
- Sibling repo: per
project_consumer_targetconvention, V4L2-side work lives outside daedalus-fourier so the kernel-library has a clean API boundary.
Status
Initial scaffold only. See docs/architecture.md for the
deeper design and docs/roadmap.md for the
sub-phase breakdown.
Repo layout
kernel/— Linux kernel module (V4L2 device registration + ioctl handling + userspace chardev bridge). Out-of-tree.daemon/— userspace decoder daemon (linkslibdaedalus_core.afrom sibling daedalus-fourier; uses dlopen for FFmpeg parser).include/— shared headers between kernel and daemon.docs/— architecture + roadmap.
License
Kernel module: GPLv2 (required for kernel-tree compatibility). Userspace daemon: BSD-2-Clause (matches daedalus-fourier).