Audio PTS are retrieved by AudioRecord.getTimestamp(), so they do not
necessarily exactly match the number of samples (this allows to take
drift and lag into account).
As a consequence, two consecutive timestamps in microseconds may
sometimes end up within the same millisecond, causing the warning. This
is particularly true for the Matroska muxer which uses a timebase of
1/1000 (1 ms precision).
Since this is "expected", lower the log level from warning to debug.
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