marfrit
c7d8050cc9
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>
81 lines
2.3 KiB
Markdown
81 lines
2.3 KiB
Markdown
# daedalus-v4l2 — roadmap
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## Sub-phases
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### Phase 8.1 — kernel module skeleton
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Out-of-tree kernel module that:
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- Registers `/dev/videoNN` with `VFL_TYPE_VIDEO` + a no-op
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V4L2 stateless dispatch table.
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- Accepts open/close, S_FMT, REQBUFS ioctls without doing
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anything (yet).
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- Builds against `/lib/modules/$(uname -r)/build`.
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Deliverable: `modprobe daedalus_v4l2` works, `v4l2-ctl --list-devices`
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shows the new device.
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### Phase 8.2 — kernel ↔ daemon chardev bridge
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- Kernel module creates `/dev/daedalus-v4l2` chardev.
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- Defines a simple req/resp protocol in `include/daedalus_v4l2_proto.h`.
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- Daemon connects, exchanges echo requests.
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Deliverable: ping-pong test passes.
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### Phase 8.3 — daemon FFmpeg dlopen + parse
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- Daemon links `libdaedalus_core.a` from sibling.
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- Daemon dlopens FFmpeg.
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- Test program: feed a VP9 IVF file to FFmpeg parsers,
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extract block-level metadata, validate against expected.
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Deliverable: daemon can parse a VP9 frame and walk the
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block-level info.
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### Phase 8.4 — VP9 end-to-end via daedalus-fourier
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- Wire daemon's per-block walker to `daedalus_dispatch_*` calls.
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- Kernel module passes bitstream + controls to daemon over
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chardev.
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- Daemon decodes, writes pixels to a shared buffer, returns
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result to kernel.
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- Kernel returns via DQBUF.
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Deliverable: `v4l2-ctl --stream-from=foo.ivf` produces
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decoded frames (output via `--stream-to` PNG dump).
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### Phase 8.5 — dmabuf / DRM PRIME
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- Kernel module allocates dma-coherent buffers.
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- Export via VIDIOC_EXPBUF.
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- Daemon writes via mmap into kernel-allocated dmabuf.
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- Test: `v4l2-ctl --capture-mmap-dmabuf` works.
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Deliverable: dmabuf-fd is exportable; first browser-friendly
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frame.
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### Phase 8.6 — AV1 + H.264
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- Add codec support for AV1 (using CDEF QPU helper) and
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H.264 (using deblock QPU helper for the one cycle 8 path,
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everything else CPU).
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Deliverable: real AV1/H.264 clips decode end-to-end.
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### Phase 8.7 — performance + 30fps@1080p
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- Profile end-to-end pipeline.
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- Eliminate copies where possible.
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- Hit 30fps@1080p for daily YouTube videos
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(the project's user-facing success criterion per
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`30fps-floor-is-fine` memory).
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Deliverable: 30fps stable on real content.
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## Effort estimate
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Each phase: ~1 week of focused work (~40 hours).
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Total: 7 weeks for v1.
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Could be split across multiple sessions / contributors.
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