Scaffold: community VC7 codec firmware (empty, Phase 0 pending)
Empty project skeleton + README laying out the wax-and-feathers rationale (VC7 is programmable silicon sitting unused; YouTube's VP9 / AV1 codecs map to Pi 5's biggest energy cost; higgs is battery-powered; saving electrons saves the planet — at least that seems to be consensus). Includes: - README.md with rationale, scope (in/out), conventions, 5 Phase-0 open questions, layout, sibling-project orbit. - docs/dev_process.md (mirror of feedback_dev_process.md). - src/, tests/ empty placeholders. No build system yet. No PKGBUILD. Phase 0 not started. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
@@ -0,0 +1,161 @@
|
||||
# daedalus-fourier
|
||||
|
||||
Community-built video codec firmware for the VideoCore VII processor
|
||||
on Broadcom BCM2712 (Raspberry Pi 5, Compute Module 5). Targets the
|
||||
codecs Pi 5's purpose-built hardware doesn't cover — primarily VP9
|
||||
and AV1 — by running software decoders on the programmable VPU cores
|
||||
already sitting on the die.
|
||||
|
||||
> Daedalus built the Labyrinth for King Minos, then escaped from it
|
||||
> by hand-forging flight firmware out of feathers and wax when no
|
||||
> sanctioned exit existed.
|
||||
|
||||
That's the project shape. The Broadcom-locked VideoCore VII is the
|
||||
Labyrinth; the Pi Foundation's "use the HEVC block and live with
|
||||
software decode for everything else" is the official non-exit; and
|
||||
this project is the wax-and-feathers attempt to make the silicon do
|
||||
what its instruction set says it can.
|
||||
|
||||
**Status: empty scaffold.** Phase 0 not yet started. Don't try to
|
||||
build this. Don't expect a milestone schedule. This is research-track
|
||||
work that may take years or may turn out structurally impossible.
|
||||
|
||||
## Why this exists (rationale)
|
||||
|
||||
higgs is a Raspberry Pi Compute Module 5 in a small portable
|
||||
chassis with a battery. Watching nerds review *Star Wars* on YouTube
|
||||
while putting Mac Studios into virtual shopping baskets is a
|
||||
core workload for the higgs class of device.
|
||||
|
||||
YouTube serves H.264 (legacy), VP9 (typical 4K), and AV1 (newer
|
||||
high-bitrate / high-resolution content). It does not serve HEVC.
|
||||
Pi 5's BCM2712 has one HW decoder block: HEVC. The intersection
|
||||
of {what YouTube serves} ∩ {what BCM2712 decodes in HW} = ∅.
|
||||
|
||||
Every YouTube frame on higgs today is software-decoded on Cortex-A76
|
||||
cores at ~50–90% CPU per video stream. Software decode at 1080p VP9
|
||||
draws roughly 4–7 W under sustained load on Pi 5. HW decode of the
|
||||
same content, if achievable, would draw under 1 W and free the CPU
|
||||
for everything else.
|
||||
|
||||
For a battery-powered higgs that's a 3–5× session-time improvement.
|
||||
For the global ~10M-unit Pi 5 install base watching mostly-VP9
|
||||
video, it's measurable embodied-electron savings. Saving electrons
|
||||
saves the planet — at least that seems to be consensus.
|
||||
|
||||
The Pi Foundation isn't going to do this work (per their own
|
||||
statement: chromium-patch sustainment was too much; firmware-codec
|
||||
sustainment would be moreso). The kernel `rpi-hevc-dec` series has
|
||||
been 17 months in review for one decoder block they DID write
|
||||
themselves. Whatever ships here ships through the community.
|
||||
|
||||
## Scope
|
||||
|
||||
### In scope (research-grade, no schedule)
|
||||
- **VideoCore VII ISA + toolchain reverse-engineering.** Extending
|
||||
the existing VC4/VC6 community work (Mesa `vc4`/`v3d`, `vc4-asm`,
|
||||
Eric Anholt's docs) to VC7. VC4's ISA is open-sourced; VC6/VC7
|
||||
is mostly extrapolation but the boot path / firmware-load
|
||||
interface is documented enough to load custom code.
|
||||
- **AV1 software decoder on VC7.** AV1 is the larger long-term win
|
||||
(newer codec, growing share, no licensing landmines comparable
|
||||
to HEVC). dav1d's reference C implementation is the porting
|
||||
target — significant work but a clean reference exists.
|
||||
- **VP9 software decoder on VC7.** Older but currently the dominant
|
||||
4K YouTube codec. libvpx as porting target.
|
||||
- **V4L2 stateless / stateful uAPI exposure.** Once firmware
|
||||
decodes, surface it as `/dev/videoNN` so existing userspace
|
||||
(ffmpeg, mpv, firefox-fourier via libavcodec) consumes it
|
||||
identically to rpi-hevc-dec. Reuse libva-v4l2-request-fourier
|
||||
+ firefox-fourier plumbing unchanged.
|
||||
|
||||
### Out of scope
|
||||
- HEVC (Pi 5 has a dedicated HW block; rpi-hevc-dec covers it).
|
||||
- Pi 4 / BCM2711 / VideoCore VI. Different ISA, smaller compute
|
||||
budget, likely insufficient for VP9/AV1 even in optimal firmware.
|
||||
- Non-Pi targets. VideoCore is Broadcom-Pi-specific silicon.
|
||||
- Encode. Pi Foundation explicitly removed all HW encode in Pi 5;
|
||||
firmware encode on VC7 is a separate (larger) project.
|
||||
- Replacing the existing GPU firmware. Custom codec firmware
|
||||
coexists with the graphics path; doesn't displace it.
|
||||
|
||||
## Conventions
|
||||
|
||||
This project follows the same 9(+1)-phase dev process as the rest
|
||||
of the fresnel/ampere/firefox-fourier campaigns. See
|
||||
`docs/dev_process.md` (mirrored from
|
||||
`~/.claude/projects/-home-mfritsche-src/memory/feedback_dev_process.md`).
|
||||
|
||||
- Phase 0 (substrate / motivation / inventory) opens the chapter.
|
||||
- Phase 5 (second-model review) is mandatory before implementation.
|
||||
- Phase 8 (package & ship) goes through `marfrit-packages` ALARM.
|
||||
- Phase 9 distills lessons into memory entries.
|
||||
|
||||
Gitea identity: `claude-noether` (per
|
||||
`feedback_gitea_as_claude_noether.md`). No `marfrit` pushes from
|
||||
Claude sessions.
|
||||
|
||||
## Open questions for Phase 0
|
||||
|
||||
Lock these empirically before Phase 1.
|
||||
|
||||
1. **Is VideoCore VII's ISA reachable from userspace today?** The
|
||||
Mesa `v3d` driver exposes compute shaders. Can arbitrary
|
||||
bytecode load via that path, or do we need a custom firmware
|
||||
loader through the mailbox interface?
|
||||
2. **What's the VC7 instruction throughput envelope?** VC4 hit ~8
|
||||
GFLOPS at full clock. VC7 has 12 cores at higher clock. Need
|
||||
actual benchmark numbers for the kind of integer / SIMD load
|
||||
AV1 / VP9 entropy decode demands. Decode is fundamentally
|
||||
serial in places — does VC7's parallel structure even help?
|
||||
3. **Is the boot / firmware-load path documented enough to load
|
||||
community firmware safely?** Pi Foundation publishes some VC
|
||||
binaries (`start.elf`, `fixup.dat`). What's the contract for
|
||||
side-loaded code that wants to coexist with the GPU path?
|
||||
4. **What's the state of the prior art?** Search Mesa community,
|
||||
Phoronix archives, Eric Anholt's old posts, Herman Hermitage's
|
||||
VideoCore reverse-engineering. The "v3d firmware decode"
|
||||
concept may have been tried and abandoned for documented
|
||||
reasons we should learn before re-doing.
|
||||
5. **Is dav1d / libvpx structurally amenable to GPU-shader-style
|
||||
parallelism, or does it assume conventional CPU execution?**
|
||||
This may be a hard architectural blocker that no amount of
|
||||
firmware brilliance fixes.
|
||||
|
||||
## Layout
|
||||
|
||||
```
|
||||
daedalus-fourier/
|
||||
├── README.md ← this file
|
||||
├── docs/
|
||||
│ └── dev_process.md ← reference copy of the 9(+1)-phase loop
|
||||
├── src/ ← empty; VC7 codec firmware lives here
|
||||
└── tests/ ← empty; unit-test rig for individual
|
||||
decode primitives
|
||||
```
|
||||
|
||||
No build system yet. No PKGBUILD. Adding those before the first
|
||||
real compilation unit is scaffold-creep.
|
||||
|
||||
## Sibling projects in the same orbit
|
||||
|
||||
- `libva-v4l2-request-fourier` — VA-API consumer-side backend.
|
||||
Would receive daedalus-fourier's decoded surfaces transparently
|
||||
once firmware exposes a V4L2 stateless / stateful node.
|
||||
- `firefox-fourier` — Firefox fork that routes stateless V4L2
|
||||
through libavcodec's `v4l2_request` hwaccel. Same pickup point.
|
||||
- `chromium-fourier` — sibling for Chromium.
|
||||
- `kernel-agent` — manages the kernel-side bring-up. The V4L2
|
||||
driver wrapping daedalus's firmware would land here.
|
||||
- `ampere-av1-enablement` — software-side AV1 bring-up on RK3588
|
||||
(rkvdec / vpu981). Provides the userspace conformance harness
|
||||
daedalus would reuse for VC7-AV1 verification.
|
||||
|
||||
## Source attribution
|
||||
|
||||
Daedalus-the-myth is public domain. The wax-and-feathers
|
||||
metaphor is older than software engineering.
|
||||
|
||||
Anyone wanting to fail at this project: please file your failures
|
||||
under `branches/icarus/`. Built-in self-deprecation slot, with
|
||||
honor.
|
||||
Reference in New Issue
Block a user