Files

T

marfrit c7d8050cc9 Initial scaffold: daedalus-v4l2 sibling repo

V4L2 stateless decoder for Pi 5, backed by sibling
daedalus-fourier kernel library (VP9 + AV1 CDEF + H.264 video
decode kernels on VideoCore VII compute + ARM NEON).

Architecture locked 2026-05-18 by mfritsche per
daedalus-fourier/docs/phase8_scoping.md:
- Option B: Linux kernel V4L2 shim + userspace daemon (not
  v4l2loopback). Real /dev/videoNN; proper DRM PRIME for
  browser zero-copy.
- Option γ: dlopen FFmpeg at runtime as parser. No vendoring;
  fastest to v1.
- Sibling repo (this repo): V4L2-side work outside of
  daedalus-fourier so kernel-library API stays clean.

Components:
  kernel/ - Linux out-of-tree kernel module (GPLv2; V4L2
    device + chardev bridge to userspace daemon)
  daemon/ - userspace decoder daemon (BSD-2-Clause; links
    libdaedalus_core.a from sibling; dlopens FFmpeg)
  docs/   - architecture + 7-phase roadmap (8.1..8.7)
  include/ - shared headers between kernel and daemon

Roadmap (7 sub-phases, ~1 week each):
  8.1 kernel skeleton (/dev/videoNN with no-op ioctls)
  8.2 chardev bridge (kernel ↔ daemon ping-pong)
  8.3 daemon FFmpeg dlopen + parse path
  8.4 VP9 end-to-end via daedalus_dispatch_*
  8.5 dmabuf / DRM PRIME for zero-copy
  8.6 AV1 + H.264 codec support
  8.7 performance: hit 30fps@1080p (project floor)

No code yet — only README + design docs + directory structure.
First implementation work starts in Phase 8.1 next session.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

2026-05-18 14:54:56 +00:00

2.3 KiB

Raw Blame History

daedalus-v4l2 — roadmap

Sub-phases

Phase 8.1 — kernel module skeleton

Out-of-tree kernel module that:

Registers /dev/videoNN with VFL_TYPE_VIDEO + a no-op V4L2 stateless dispatch table.
Accepts open/close, S_FMT, REQBUFS ioctls without doing anything (yet).
Builds against /lib/modules/$(uname -r)/build.

Deliverable: modprobe daedalus_v4l2 works, v4l2-ctl --list-devices shows the new device.

Phase 8.2 — kernel ↔ daemon chardev bridge

Kernel module creates /dev/daedalus-v4l2 chardev.
Defines a simple req/resp protocol in include/daedalus_v4l2_proto.h.
Daemon connects, exchanges echo requests.

Deliverable: ping-pong test passes.

Phase 8.3 — daemon FFmpeg dlopen + parse

Daemon links libdaedalus_core.a from sibling.
Daemon dlopens FFmpeg.
Test program: feed a VP9 IVF file to FFmpeg parsers, extract block-level metadata, validate against expected.

Deliverable: daemon can parse a VP9 frame and walk the block-level info.

Phase 8.4 — VP9 end-to-end via daedalus-fourier

Wire daemon's per-block walker to daedalus_dispatch_* calls.
Kernel module passes bitstream + controls to daemon over chardev.
Daemon decodes, writes pixels to a shared buffer, returns result to kernel.
Kernel returns via DQBUF.

Deliverable: v4l2-ctl --stream-from=foo.ivf produces decoded frames (output via --stream-to PNG dump).

Phase 8.5 — dmabuf / DRM PRIME

Kernel module allocates dma-coherent buffers.
Export via VIDIOC_EXPBUF.
Daemon writes via mmap into kernel-allocated dmabuf.
Test: v4l2-ctl --capture-mmap-dmabuf works.

Deliverable: dmabuf-fd is exportable; first browser-friendly frame.

Phase 8.6 — AV1 + H.264

Add codec support for AV1 (using CDEF QPU helper) and H.264 (using deblock QPU helper for the one cycle 8 path, everything else CPU).

Deliverable: real AV1/H.264 clips decode end-to-end.

Phase 8.7 — performance + 30fps@1080p

Profile end-to-end pipeline.
Eliminate copies where possible.
Hit 30fps@1080p for daily YouTube videos (the project's user-facing success criterion per 30fps-floor-is-fine memory).

Deliverable: 30fps stable on real content.

Effort estimate

Each phase: ~1 week of focused work (~40 hours). Total: 7 weeks for v1.

Could be split across multiple sessions / contributors.

2.3 KiB Raw Blame History