feat: promote linux native audio path

crates/chanora_audio/Cargo.toml

@@ -9,6 +9,10 @@ license.workspace = true
 repository.workspace = true
 publish.workspace = true
 
+[features]
+default = []
+bench-harness = ["dep:criterion", "dep:dhat", "dep:serde_json"]
+
 [dependencies]
 chanora_protocol = { path = "../chanora_protocol" }
 thiserror.workspace = true
@@ -29,10 +33,13 @@ audiopus = "0.3.0-rc.0"
 tsclientlib = { git = "https://github.com/ReSpeak/tsclientlib.git", rev = "04aa2491", default-features = false, features = ["audio"] }
 tokio = { version = "1", features = ["sync", "rt", "macros", "time"] }
 rustfft = "6.2.0"
+criterion = { version = "0.5", optional = true }
+dhat = { version = "0.3", optional = true }
+serde_json = { version = "1", optional = true }
 
 [target.'cfg(all(not(target_os = "android"), not(target_os = "ios"), not(target_os = "macos")))'.dependencies]
-# Desktop audio I/O for Windows capture/playback and Linux capture.
-# Linux playback uses SDL2; Apple platforms use direct VoiceProcessingIO
+# Desktop audio I/O for Windows capture/playback and Linux fallback metadata.
+# Linux voice I/O uses PipeWire first and PulseAudio as fallback; Apple platforms use direct VoiceProcessingIO
 # AudioUnits via `coreaudio-rs` for the voice path.
 cpal = "0.17.3"
 
@@ -101,34 +108,33 @@ tokio = { version = "1", features = ["sync", "rt", "macros", "time", "test-util"
 # Cross-platform recording Layer for the SDD-090 / DEC-027 privacy
 # invariant integration test (`tests/ptt_privacy.rs`).
 tracing-subscriber = { version = "0.3", features = ["registry"] }
-# SDD-120 §3 — criterion bench harness (realtime_capture / opus_codec /
-# resampler). `harness = false` per bench entry below disables the
-# default libtest harness so criterion can install its own.
-criterion = "0.5"
-# SDD-120 §3 item 1 — dhat is used as the global allocator inside
-# `benches/realtime_capture.rs` to count post-warmup heap allocations
-# on the realtime capture path. Dev-dep only — does NOT affect
-# production builds.
-dhat = "0.3"
-# SDD-120 §5 / §8 — JSON serialization for `emit_baseline` /
-# `compare_baseline` binaries that consume criterion's per-bench
-# `estimates.json` outputs and emit the SRS-217 baseline schema.
-serde_json = "1"
-
 [[bench]]
 name = "realtime_capture"
 harness = false
 path = "benches/realtime_capture.rs"
+required-features = ["bench-harness"]
 
 [[bench]]
 name = "opus_codec"
 harness = false
 path = "benches/opus_codec.rs"
+required-features = ["bench-harness"]
 
 [[bench]]
 name = "resampler"
 harness = false
 path = "benches/resampler.rs"
+required-features = ["bench-harness"]
+
+[[example]]
+name = "compare_baseline"
+path = "examples/compare_baseline.rs"
+required-features = ["bench-harness"]
+
+[[example]]
+name = "emit_baseline"
+path = "examples/emit_baseline.rs"
+required-features = ["bench-harness"]
 
 [target.'cfg(target_os = "linux")'.dependencies]
 # GNOME-on-Wayland Global Push-to-Talk uses the freedesktop
@@ -148,22 +154,8 @@ futures-util = { version = "0.3", default-features = false, features = ["std"] }
 # options. The portal recommends fresh tokens to scope its own
 # object paths per call.
 rand = "0.8"
-# SDL2 audio for Linux. Replaces the cpal playback path on Linux only;
-# cpal stays in use for Linux capture and Windows capture/playback.
-# Apple platforms use direct VoiceProcessingIO AudioUnits. Rationale: the
-# cpal Linux backend opens raw ALSA `default`, which on most Arch
-# / Fedora / Debian installs routes through `dmix` + `plug` with
-# nearest-neighbour resampling and very small period sizes — the
-# combination produces audible crackling/popping. SDL2 on the same
-# systems routes through PipeWire's PulseAudio compat bridge (or
-# real PulseAudio), both of which carry a high-quality resampler
-# and a sensible default period. The upstream tsclientlib audio
-# example (`tsclientlib/examples/audio_utils/ts_to_audio.rs`) and
-# the official Qint client both use SDL2 in exactly this shape;
-# this dep brings Chanora in line with that pattern.
-#
-# `bundled` is OFF deliberately — we link against the system
-# libSDL2.so. Arch ships `sdl2-compat`; Debian/Ubuntu ship
-# `libsdl2-2.0-0`; Fedora ships `SDL2`. The chanora-flutter Linux
-# build documentation lists this as a runtime dependency.
-sdl2 = { version = "0.37", default-features = false }
+# Linux-native voice I/O. PipeWire is primary on modern desktops;
+# PulseAudio is retained as fallback and for older environments.
+pipewire = { version = "0.10", features = ["v0_3_44"] }
+libpulse-binding = "2.30"
+libpulse-simple-binding = "2.29"