enricobuehler
fc5b6296e3
WP1 of design/presenter-cadence-rework-implementation-plan.md. Shared core
type plus the Android binding; desktop and Apple follow.
Every stat we publish is a latency — a difference between two points on one
frame. No latency can see judder, because judder is a property of the
SEQUENCE. A stream that shows each frame one refresh early and the next one
late has excellent percentiles and looks broken; a stream whose every
interval is exactly two refreshes has worse latency than one alternating 1
and 3, and looks perfect. That blind spot is why a smoothness complaint
could not be confirmed or refuted from our own telemetry.
PresentIntervals quantises the spacing between consecutive on-glass instants
onto the learned panel grid and reports the modal spacing plus the fraction
of intervals that miss it — the judder number, in permille to match the
phase coherence already next to it. Scale-free: the mode absorbs the cadence
ratio, so 60-on-120 and 120-on-120 are both "one tall bucket" and directly
comparable. That is what makes it usable as one ruler across clients,
refresh rates and stream rates, and for a feature-on/off A/B.
Deliberate choices, each with a test:
- fed the MEASURED on-glass instant, never the requested present time,
which would measure our own intent and always look perfect
- fed SurfaceFlinger's raw CLOCK_MONOTONIC render stamp, not the
realtime-rebased one the latency stats use: cadence is about spacing,
and a realtime clock step would forge a hitch that never happened
- stalls (>8 refreshes) and out-of-order callbacks counted apart from the
ratio, so a window that looks smooth because the stream was PAUSED
cannot be mistaken for a good one
- sub-refresh jitter is not judder: the display quantises it away, so the
metric must too
- the predecessor survives a window drain, else one interval per window
would go unscored forever
Always-on via the 1 Hz pf.present line, so the HUD-off wireless A/B the
baseline measurement needs is readable from logcat. HUD surfacing waits on
the stats-unification spec amendment (plan S3) and on the in-flight HUD work.
Gates: punktfunk-core 189 tests green (10 new); cargo ndk check + clippy
arm64 clean — the 5 remaining warnings are pre-existing and in other files.
punktfunk — Android client (phone & TV)
The native Android app for streaming a punktfunk host to your phone, tablet, or Android TV. A Compose app that finds hosts on your network, pairs with a PIN, and streams at the display's own resolution — with hardware HEVC decode, HDR10, and controller support, built for both touch and the couch (D-pad / gamepad focus navigation).
Features
- Hardware decode — NDK
AMediaCodecHEVC →SurfaceView, including HDR10 (Main10 / BT.2020 PQ), with low-latency tuning and a live stats HUD. - Audio both ways — Opus + AAudio playback with a jitter ring, plus mic uplink to the host.
- Controller support — buttons + axes with rumble and HID feedback (lightbar / adaptive triggers); D-pad / gamepad focus navigation for TV and phone.
- Find hosts automatically — native mDNS discovery; first connect does a one-time SPAKE2 PIN pairing (or TOFU on trusted LANs), then reconnects on a Keystore-wrapped, pinned identity.
- Compose UI — Connect / Settings / Stream screens with Material You theming.
Built for arm64-v8a + armeabi-v7a + x86_64 — the 32-bit armeabi-v7a slice is what keeps the
app installable on the many 32-bit Google TV / Android TV streamers (Walmart onn. 4K, Chromecast with
Google TV, budget Amlogic boxes) that otherwise reject a 64-bit-only build as "not compatible".
Get it
Published to Google Play (Internal Testing) — join the beta via the Discord. Per-device setup and pairing: docs.punktfunk.unom.io/docs/install-client.
How it's built — Rust-heavy
Kotlin can't import the cbindgen C header the way Swift can, so a native bridge is unavoidable. We
write it in Rust and link punktfunk-core directly — so the Android client reuses the Linux
client's orchestration (audio jitter ring, VK keymap inverse, latency/skew math, capture state
machine, trust logic) instead of re-porting it into Kotlin.
| Side | Owns |
|---|---|
Rust (native/ → libpunktfunk_android.so) |
the JNI seam, NativeClient (QUIC control + UDP data plane), AnnexB → AMediaCodec decode (incl. HDR10), Opus + AAudio audio + mic, controller feedback, latency math, trust/pairing, mdns-sd discovery |
Kotlin (app/, kit/) |
Compose UI, SurfaceView lifecycle, input capture, the Wi-Fi MulticastLock + permission UX, Keystore identity |
The single seam is io.unom.punktfunk.kit.NativeBridge ⇄ Java_io_unom_punktfunk_kit_NativeBridge_*.
native/ Rust cdylib (workspace member) — links punktfunk-core directly
src/lib.rs crate doc · JNI_OnLoad · version probes
src/session/ session lifecycle: connect/pair + trust, plane start/stop, input shims
src/decode.rs AnnexB → AMediaCodec HEVC hardware decode → SurfaceView (incl. HDR10)
src/audio.rs · src/mic.rs Opus + AAudio playback / mic uplink
src/feedback.rs · src/stats.rs rumble + HID feedback; live video stats
src/discovery.rs native mdns-sd browse of the host's _punktfunk._udp advert
app/ :app — Compose UI: Connect / Settings / Stream (phone + TV)
kit/ :kit — NativeBridge · native mDNS discovery · Gamepad · Keymap · Keystore identity
Build & run
Prerequisites: Android SDK + NDK r30 (30.0.14904198), platforms;android-37.0,
build-tools;37.0.0, cmake;3.22.1 (builds libopus); JDK 21 (AGP 9.2 runs on JDK 17–21, not
a newer default); Rust with rustup target add aarch64-linux-android armv7-linux-androideabi x86_64-linux-android and
cargo install cargo-ndk. Toolchain is pinned (AGP 9.2 · Gradle 9.4.1 · Kotlin 2.3.21 · Compose BOM
2026.05.01 · compileSdk 37 · minSdk 28).
Android Studio: open clients/android — it uses its bundled JBR 21, and the cargoNdk* task
builds the .so as part of the normal build.
CLI (point Gradle at JDK 21 if your machine default is newer):
export JAVA_HOME="$(/usr/libexec/java_home -v 21)" # or your Temurin 21 path
cd clients/android
./gradlew :app:assembleDebug # cargo-ndk cross-compiles libpunktfunk_android.so first
./gradlew :app:installDebug # onto a running emulator/device
# emulators from env setup: emulator -avd pf_phone | emulator -avd pf_tv
The debug APK lands in app/build/outputs/apk/debug/. Launch it, pick a host, pair, and stream.
Related
- Documentation — quick start, pairing, troubleshooting
- Project README — the host, the other clients, and how it all fits together