The 5dc24a0 low-latency overhaul regressed badly on some phones. Every piece
of it — decoder ranking, per-SoC vendor keys, the async decode loop, pipeline
thread boosts, the ADPF max-performance bias, game-tagged AAudio, DSCP marking,
the Wi-Fi low-latency lock, HDMI ALLM and the forced TV mode switch — now rides
the "Low-latency mode (experimental)" toggle, default OFF. Off restores the
pre-overhaul pipeline byte-for-byte: the sync poll loop, the platform-default
decoder, and the original format keys (standard low-latency + blind Qualcomm
twin + priority=0 + operating-rate=MAX together).
- New pref key (low_latency_mode_experimental): the old key shipped default-ON,
so any install that ever saved settings persisted true — flipping the default
under the old key would leave exactly the regressed devices stuck on.
- DSCP is applied at socket creation, so the toggle reaches the transport via
NativeBridge.nativeSetLowLatencyMode → transport::set_dscp_default, called in
the connect choke point before nativeConnect; the core DSCP default reverts
to off everywhere.
- nativeStartAudio(handle, lowLatencyMode) gates AAudio usage=Game.
- VideoDecoders.pickDecoder now skips `.secure` decoder twins and decoders that
require FEATURE_SecurePlayback: they need a secure surface, and a secure twin
could out-score its plain sibling (only it advertising FEATURE_LowLatency),
which black-screens a clear stream.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Close the latency gap on the Android client with per-SoC decoder tuning, an
event-driven decode loop, and full system integration.
- Decoder selection: rank MediaCodecList decoders in Kotlin (hardware/vendor
preferred, software avoided, FEATURE_LowLatency probed) and create the chosen
one by name. Per-SoC low-latency keys gated on the codec-name prefix: Qualcomm
picture-order + low-latency, Exynos (also Google Tensor), Amlogic, HiSilicon;
MediaTek vdec-lowlatency set unconditionally. operating-rate = MAX (Qualcomm)
vs priority = 0 (else) are mutually exclusive. NVIDIA/Rockchip/Realtek have no
vendor key — covered by ranking + the standard low-latency key.
- Async decode loop: AMediaCodec async-notify replaces the poll loop, presenting a
decoded frame the instant it is ready instead of waiting out a poll interval.
Behind USE_ASYNC_DECODE with the synchronous loop kept for A/B during bring-up.
- System integration: Wi-Fi FULL_LOW_LATENCY lock and HDMI ALLM
(setPreferMinimalPostProcessing) for the stream's lifetime; game_mode_config.xml
opting out of OEM downscaling / FPS overrides.
- Pipeline: boost the data-plane pump + audio thread priorities, AAudio usage=Game,
DSCP marking on by default on Android, ADPF setPreferPowerEfficiency(false),
and setFrameRateWithChangeStrategy(ALWAYS) to force the HDMI mode switch on TV.
- lowLatencyMode master toggle (default on) as the escape hatch; the stats HUD now
shows the resolved decoder name.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Three levers to lower and steady decode latency on Snapdragon (Adreno) devices:
- ADPF (Adaptive Performance Framework): a new dlsym-resolved hint session
(native/src/adpf.rs; API-33+, resolved at runtime so there's no build-time
link dependency and libpunktfunk_android.so still loads on API 31/32) tells
the CPU governor the video pipeline runs a per-frame real-time workload, so it
keeps those threads on fast cores at high clocks. It now covers all three
latency-critical threads — the pf-decode feed/drain/present loop, the core
data-plane pump (UDP receive + FEC reassembly), and the audio thread — via a
new generic hot-thread registry on NativeClient (register_hot_thread /
hot_thread_ids; the pump self-registers). The session is built lazily on the
first presented frame, since ADPF createSession rejects a set containing any
not-yet-live tid.
- operating-rate -> Short.MAX ("as fast as possible"): pushes the Qualcomm
decoder to run each frame at max clocks instead of merely sustaining the
display rate at a power-saving clock that adds per-frame decode latency.
- appCategory="game": makes the app eligible for OEM Game Mode / Game Dashboard
performance profiles.
The core registry is cross-platform (gettid on Linux/Android, a no-op
elsewhere) — no Android-specific pollution of the shared core. Host workspace +
64 core tests green; Android arm64-v8a + x86_64 (platform 31) build + clippy
clean. On-device Snapdragon validation pending.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehlerandClaude Fable 5