Background:
1. When the player has multiple audio renderers, by default they share a
single AudioSink.
2. When any new renderer is enabled, all disabled renderers are reset
prior to the new renderer being enabled. This is to give them a chance
to free up resources in case the renderer being enabled needs them. These
reset calls are expected to be no-ops for renderers that have never been
enabled.
The issue:
The problematic case arises when there are two audio renderers and a third
renderer (e.g., text) is being enabled. In this case, the disabled audio
renderer's reset call ends up resetting the AudioSink that's shared with the
enabled audio renderer. The enabled audio renderer is then unable to make
progress, causing playback to freeze.
This is a minimal fix that directly prevents the mentioned issue. There are
multiple follow-ups that would probably make sense:
1. Having ExoPlayerImplInternal track which renderers need to be reset, and
only resetting those renderers rather than all that are disabled. This
seems like a good thing to do regardless, rather than relying on those
calls being no-ops.
2. If we want to continue sharing AudioSink, we need to formalize this much
better and make sure we have good test coverage. Messages like
MSG_SET_VOLUME are also delivered to the AudioSink multiple times via
each of the renderers, which works currently because DefaultAudioSink
no-ops all but the first call in each case. This is pretty fragile though!
Issue: #8203
#minor-release
PiperOrigin-RevId: 343296081
8c8176647c