150 s boot with --apu=alsa --mute=false, tee in front of the paced pulse slave.
PulseAudio monitor, default 5.3 ms 39.3 percent silence 30.5 gaps/s
PulseAudio monitor, 200 ms 15.6 percent silence 3.5 gaps/s
PulseAudio monitor, 500 ms 50.1 percent silence 1.3 gaps/s
ALSA tee to paced pulse slave 9.98 percent silence 8.37 gaps/s
106.2 s captured over about 151 s of wall clock, i.e. 0.70x real time: the file
is SHORT rather than gap-riddled, which is the intended trade. Six distinct
channels, no duplicates, sensible peaks.
A format trap worth recording: xenia s ALSA driver is SND_PCM_FORMAT_FLOAT_LE and
its log confirms 6 channels, so the raw tee is float32 and not s16. Reading it as
s16 yields a plausible-looking file whose giveaway is peaks alternating exactly
-0.00 / -4.82 across channels -- the two halves of each float landing in
alternate channels. I measured it wrongly that way first.
The residual 10 percent silence is not removed, but its meaning has changed. It
is no longer invented by PulseAudio s monitor; the tee records exactly what Xenia
wrote, and Xenia wrote silence, because its writer thread pads whenever the guest
has not filled the ring. So the capture is faithful -- every sample in it is a
sample the emulator emitted -- while the emulator is still padding, because the
guest runs at about 0.7x real time here. No capture method can remove that.
So this is a 3.9x improvement in silence and a change of attribution, not a clean
capture. At 9.98 percent and 8.37 gaps/s it sits right on the port s fail bar,
and should not be treated as an oracle without saying which side of the line it
fell on.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QsEPXWVaEpyfudtR6re1Pd
371cd0d610