Use double microseconds for tracking back/front timestamp in AudioClock.
Back timestamp is computed by summing the new frames_written for every
call to WroteAudio. The number of microseconds per frame is often not
a whole number (e.g. 20.833 mu for sample rate of 48Khz). Prior to this
change, using TimeDelta to do the summing of frames_written meant we
truncated to the nearest microsecond with every call to WroteAudio. The
truncation error slowly accumulates in the back timestamp. After 2
hours of playback this error causes noticeable audio/video sync drift.
Having front_timestamp be a double is less critical. Front timestamp
is computed using back_timestamp at every call to WroteAudio, so fixing
back implicitly fixes front. Still, I've changed them both to double
for the sake of consistency and a slight improvement in accuracy.
BUG=564604
Review URL: https://codereview.chromium.org/1711473002
Cr-Commit-Position: refs/heads/master@{#376287}
(cherry picked from commit 2ed08018de0593b905c18500c1784464dcbe5468)
Review URL: https://codereview.chromium.org/1729273003 .
Cr-Commit-Position: refs/branch-heads/2623@{#503}
Cr-Branched-From: 92d77538a86529ca35f9220bd3cd512cbea1f086-refs/heads/master@{#369907}
3 files changed
