Two playback-audio defects found while chasing periodic pops, clipped
words and repeated phrases:
1. The playback clocks are created at engine init with the fallback
rate (hd_1080p25) and never updated, while audio chunks are sized by
the SEQUENCE time base (30/1 from the broken default). The playhead
advanced at 25 fps but each chunk carried only 1600 samples, so
production ran at 40000 samples/s against the device's 48000 -- ~17%
of playback time was zero-filled silence (clipped words). tick() now
syncs both clocks to the sequence's actual rate.
2. The underrun self-heal cleared the whole device queue (~190 ms of
unheard content skipped), reset the prefetch (whose first
re-rendered chunk was then always dropped as late) and re-anchored
the master clock, re-rendering already-played audio whenever the
playhead lagged (audible as a pop plus a repeated phrase, every
~1.1 s). It now trims just the stale lead from the queue
(PreviewAudioDevice::drop_front_frames): the zero-fill already
advanced the output clock past that content, so the rest of the
queue stays audible and the anchor stays valid.
Also adds the OAK_DEBUG_AUDIO event log used to diagnose all of this
(prefetch resets, late drops, underruns, heals, reanchor jumps,
per-tick queue state).
Mike-Solar
84caa3589b