An underrun is audible and nothing counted it. When the ring is empty
BufferedStreamer.Stream zeroes the caller's buffer and returns ok, so a
run of zeros is spliced into the waveform and the step discontinuity at
each edge is a click; a series of short ones is static. That is the one
candidate in #135 whose audible signature matches the report.
`starved` and `starvedSince` already existed, from #122's stall fix,
and could not answer this: they are a *stall* detector, reset by every
arriving sample, because their job is to end a track whose source has
died and a merely slow source must not be cut short. That reset is
exactly what made the audible case invisible -- a hundred 20ms
underruns a minute never approach the give-up threshold, so they were
invisible to the log, to the UI and to every tier.
UnderrunStats counts runs, calls and samples for the life of the
streamer. Runs is the number that means something audible: one episode
is one pop however many callbacks it spans, and the ratio of runs to
calls is what separates clicking from dropping out.
Three things about the reporting are deliberate.
**Counting is in Stream and reporting is not.** Stream runs on the
speaker callback's real-time deadline, so a log line there would
allocate, format and write on the exact path whose missed deadline is
the defect -- measuring by making it worse. The count is two increments
under a lock that was already held; the report is on the 1 Hz position
ticker, which only runs while playing.
**An unchanged count is not logged**, which is emitStatus' rule one
package over. A healthy player is silent, so anything in the log is
news and the line appears exactly while it is popping.
**It is Info rather than Debug.** The default level is Info and a phone
has no convenient way to set YJ_LOG_LEVEL, so a debug line here would
be a counter nobody on the affected platform could read -- which is the
shape of the bug that made #160 necessary.
underrunDelta clamps at zero because the counter belongs to the
streamer and the streamer is replaced on every track: a baseline
carried across that boundary is the previous track's total subtracted
from a fresh zero. The baseline is reset at the load as well; a
negative count in a log line reads as a broken instrument and would
discredit the measurement this exists to make.
This is the instrument, not a fix. What it measures is on the issue.
