AudioTrack doesn't automatically ramp up the volume after a flush
(only when resuming with play after a pause), which causes audible
pop sounds in most cases. The issue can be avoided by manually
applying a short 20ms volume ramp, the same duration used by the
platform for the automatic volume ramping where available.
Together with the already submitted 6147050b90, this fixes the
unwanted pop sounds for most cases in the desired way. It only
leaves two cases that are not handled perfectly:
- If the media file itself contains a volume ramp at the beginning,
we wouldn't need this additional ramping. Given the extremely
short duration, this seems ignorable and we can treat it as a
future feature request to mark the beginning of media in a special
way that can then disable the volume ramping.
- For seamless period transitions where we keep using the same
AudioTrack, we may still get a pop sound at the transition. To
solve this, we'd need a dedicated audio processor to either ramp
the end of media down and the beginning of the next item up, or
apply a very short cross-fade. Either way, we need new signalling
to identify cases where the media originates from the same source
and this effect should not be applied (e.g. when re-concatenating
clipped audio snippets from the same file).
PiperOrigin-RevId: 676860234
5e3dcea1bf