enricobuehlerandClaude Opus 5
3055e29ebb
Phases 0-3 of design/audio-quality-and-latency.md, host side.
**WP2.1 — the 2026-08-03 root cause.** The client-only loopback preference took Steam's
Streaming *Microphone* render endpoint over real hardware unconditionally, because it is
silent on the host. But that endpoint exists to carry remote VOICE, and nothing checked
whether it could carry music: on the reporter's box it won all 31 loopback opens across 25
sessions while a clean AMD HD Audio endpoint sat idle, and the whole desktop mix went
through it before reaching Opus. A silent sink now has to EARN its preference — if its mix
format narrows the mix it drops below real hardware. It is still taken when nothing better
exists (narrow audio beats no audio), but flagged so the capture side says why.
`plan_with_formats` takes a probe rather than reading WASAPI, so all 26 wiring-plan tests
still run on every platform. An unknown format counts as fine, which is asserted:
`unknown_formats_reproduce_the_formatless_plan` proves a probe failure can never make the
plan worse than it was before formats existed.
**WP0.1 — log the endpoint's ACTUAL mix format.** Everything the old log printed ("48 kHz
f32 channels=2") was our REQUEST; with `autoconvert` WASAPI converts silently from whatever
the endpoint really runs. That is why a 3,600-line log filed over an audio-quality
complaint contained nothing that could diagnose it.
**WP0.2 — count what we drop.** The capture->encode handoff was a silent lossy `try_send`:
a stalled encode thread lost chunks, the encoder concatenated across the hole, and nothing
recorded it — a click plus a permanent shift of everything after. Now counted and warned,
alongside per-window peak/RMS/delivered% so a quiet host, a broken endpoint and a stream we
are damaging ourselves stop looking identical.
**WP2.4 — stop the default-device tug-of-war.** In Assert mode the capture is bound to the
planned endpoint EXPLICITLY, so a hijacked default changes only where apps render — the old
full reopen tore the capture down for nothing. The field log shows the cost: something
re-set the default every ~4 s and each round was a teardown, a wiring pass with
IPolicyConfig writes, and an audible dropout — seven in sixteen seconds, one ending in a
2 s error backoff. Now: put the default back, keep the stream, and after four rounds in
twenty seconds concede for a minute and say so once.
**WP1.1/1.2 — encode quality.** Constrained VBR (the hard-CBR comment justifies itself with
GameStream's audio FEC, which this plane does not have) and `AudioTier::High` by default:
stereo 128 -> 256 kbps, ~1 % of a 20 Mbps session. GameStream's encoder is deliberately
untouched — its FEC really does need fixed-size packets.
**WP3.1 — redundant `0xD2` plane**, sent when the client asked for it.
**WP2.2 — `audio.output_mode`** as a first-class setting (`client_only` / `host_and_client`
/ `follow_default`), superseding the two undocumented env vars, which stay honoured. The
enum lives in pf-host-config, which is deliberately dependency-free, so the tier table stays
in core where the codec knowledge is.
`capture_policy.rs` is split out for the same reason `wiring_plan.rs` is: both encode field
behaviour, so their tests must run on Linux CI, not only on a Windows box. That split
immediately earned itself — `capture_stats_separate_silence_from_signal` caught RMS being
divided by the FRAME count while summed over interleaved SAMPLES, which inflated it by
sqrt(channels) and made a sine report an RMS equal to its own peak.
WP4.5 (open the loopback at the minimum device period) is deliberately NOT done: in shared
mode `IAudioClient::Initialize` cannot change the engine period at all, so it would be a
no-op at best and a new failure path at worst. Recorded in the code. WP2.3 (force the parked
endpoint's volume) is deferred — `wasapi` keeps IMMDevice private, so it needs new raw COM
on a path this tree cannot compile, let alone test; its diagnostic half ships as the RMS
line above.
Verified: punktfunk-host + pf-host-config clippy --all-targets -D warnings and the audio
test suite under Linux/docker (gate proven non-vacuous with a planted type error); 26
wiring-plan tests standalone; fmt. The Windows-only halves of wasapi_cap.rs and
audio_control.rs are NOT compile-verified anywhere yet.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
punktfunk-host
The streaming host — the program you run on the machine whose desktop or games you want to stream. For each client that connects, it spins up a virtual display sized to that device, captures it on the GPU, encodes with hardware NVENC/VAAPI/AMF/QSV, and sends it out over a low-latency transport — no physical monitor, no letterboxing, no rearranging your real screens.
It speaks two protocols from one process:
- GameStream — so any Moonlight / Artemis client works day one.
punktfunk/1— punktfunk's own faster protocol (QUIC control plane, GF(2¹⁶) FEC + AES-GCM data plane) that the native clients use.
Runs on Linux (the primary, most battle-tested path) and Windows (x64). The shared protocol,
FEC, and crypto live in punktfunk-core; this crate is everything
platform-facing around it.
What it does
- Per-client virtual displays at the exact WxH@Hz. Linux uses per-compositor backends — KWin, gamescope, Mutter, and Sway/wlroots; Windows uses its own all-Rust IddCx virtual display, even on the secure desktop (UAC / lock screen).
- GPU zero-copy capture → encode. dmabuf → CUDA/Vulkan → NVENC on Linux; on Windows the host pushes frames straight into its own IDD (sealed IDD-push, no screen-scraping) → GPU encode. Encoders auto-select by GPU vendor: NVENC (NVIDIA), VAAPI (Linux AMD/Intel), AMF/QSV (Windows AMD/Intel), or software H.264 as a floor. HDR/10-bit and HEVC 4:4:4 supported.
- Input injection. Mouse/keyboard (libei / gamescope EIS / wlr / Windows SendInput) and virtual gamepads — Xbox 360/One, DualSense, DualShock 4 — with rumble and HID feedback back-channels.
- Audio both ways. Opus audio host→client, plus a virtual microphone the client can talk into.
- Trust & discovery. A persistent host identity, SPAKE2 PIN pairing (default) or TOFU, and mDNS auto-advertisement so clients find the host without typing an IP.
- Management API + web console. A REST API (
mgmt.rs, OpenAPI atapi/openapi.json) drives status, paired devices, and on-demand pairing; the browser UI is inweb/.
Run it
punktfunk-host serve runs inside your desktop session. Bare serve is the secure native-only
default (punktfunk/1 + the management API); add --gamestream on a trusted LAN to also accept
stock Moonlight clients.
# Linux, from the repo root (see the repo README "Running on this box" for the headless recipe):
cargo run -rp punktfunk-host -- serve # native-only (secure default)
cargo run -rp punktfunk-host -- serve --gamestream # + Moonlight compatibility
Then pair from the web console (https://<host-ip>:47992) or the client app.
Most people should install a package rather than run from source — see
packaging/ (apt · rpm/COPR/bootc · Arch/sysext · Windows installer) and
the per-platform guides at docs.punktfunk.unom.io/docs/install.
Subcommands
| Command | Purpose |
|---|---|
serve |
The host (native punktfunk/1 + mgmt API; --gamestream adds Moonlight). |
punktfunk1-host |
Standalone native-protocol listener for testing/measurement (--source virtual, --max-sessions). |
openapi |
Print the management-API OpenAPI spec (regenerates api/openapi.json). |
library |
Inspect the multi-store game library. |
service · driver · web |
Windows: SCM service, driver install, bundled web console. |
*-test / *-selftest / *-probe |
Diagnostics (input, zero-copy, HDR, compositor, gamepads). |
--help lists them all.
Layout
src/
main.rs CLI + subcommand dispatch
config.rs · session_plan.rs · session_tuning.rs · pipeline.rs session setup + the frame pipeline
vdisplay/ per-compositor virtual outputs (kwin · gamescope · mutter · wlroots)
capture/ · capture.rs screen/dmabuf capture (+ Windows IDD-push)
encode/ · encode.rs per-GPU encoders (nvenc · vaapi · ffmpeg_win (AMF/QSV) · sw)
linux/zerocopy/ dmabuf → CUDA → NVENC bridges (EGL/GL tiled, Vulkan LINEAR)
inject/ · inject.rs input backends (libei · wlr · uinput gamepads · UHID DualSense/DS4)
audio/ · audio.rs Opus out + virtual mic (PipeWire / WASAPI)
gamestream/ Moonlight compat: nvhttp · pairing · rtsp · control · stream · gamepad · apps
native.rs the native punktfunk/1 host (QUIC control + native-thread UDP data plane)
mgmt.rs · native_pairing.rs · stats_recorder.rs management API, pairing, perf capture
hdr.rs · library.rs HDR metadata; multi-store game library
linux/ · windows/ platform-confined backends
Related
punktfunk-core— the shared protocol · FEC · crypto core- Clients — the apps that connect (Apple · Linux · Windows · Android · probe)
- Packaging & docs — install & operate
- punktfunk-planning (internal planning repo) — architecture rationale and deep-dive plans