ALSA duplex bridge example (hardware testing Setup 1)#20
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examples/alsa_bridge.cpp implements the two-device real-clock harness from docs/HARDWARE_TESTING.md Setup 1: a capture thread blocks on snd_pcm_readi (paced by the input device's crystal) and feeds asrc.push(), a playback thread feeds snd_pcm_writei from asrc.pull() (paced by the output device's crystal). Per-second status line on stdout, optional --csv telemetry log, optional --dump of the post-ASRC float stream for offline analysis, and --tone <hz> to push a synthetic sine still paced by the input device's real clock. Negotiates FLOAT_LE with S16_LE fallback, recovers from xruns via snd_pcm_recover, clean SIGINT shutdown. examples/CMakeLists.txt guards the new srt_alsa_bridge target behind find_package(ALSA QUIET) so non-Linux CI configures unchanged; verified with -DCMAKE_DISABLE_FIND_PACKAGE_ALSA=ON. Built warning-clean under the srt_warnings flags (-Wall -Wextra -Wpedantic -Wconversion -Wshadow); smoke-tested --help, bad-option handling, and graceful failure when no audio device exists. https://claude.ai/code/session_01HuAFfoeD5a5Xe5aGNA16M9
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The Setup 1 deliverable from docs/HARDWARE_TESTING.md: a real-clock test harness bridging two independent ALSA devices through the converter — the canonical two-USB-dongle Raspberry Pi soak test.
What's in here
examples/alsa_bridge.cpp: capture thread (blockingsnd_pcm_readi→push()) and playback thread (pull()→snd_pcm_writei); CLI for devices/rate/channels/period/latency; once-per-second status line plus optional--csvtelemetry log (time_s,state,ppm,fill,underruns,overruns,resyncs) and--dumpof the post-ASRC float stream for offline analysis with the notebook tooling;--tonemode keeps the read cadence on the input device's real crystal but pushes a synthetic sine (clean-signal soak without trusting dongle analog); SIGINT-clean shutdown.snd_pcm_recover, fatal only if recovery fails; non-exactset_rate_nearis a hard error (both domains must be nominally equal for a near-unity ASRC).examples/CMakeLists.txt: built only whenfind_package(ALSA)succeeds — macOS/Windows/no-ALSA configures verified unaffected (including with-DCMAKE_DISABLE_FIND_PACKAGE_ALSA=ON).Verified
Warning-clean under the project flags;
--help/bad-args/no-device paths exit gracefully. Not verified: actual audio I/O — no hardware here. This is the piece you point at a Pi with two dongles; the README's hardware-testing doc now references the workflow.https://claude.ai/code/session_01HuAFfoeD5a5Xe5aGNA16M9
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