This optimization allows a ChunkSampleStream to output track
formats as soon as they're parsed during an InitializationChunk
load, rather than waiting until after the InitializationChunk
load is completed.
In DASH VOD, a single InitializationChunk typically loads the
moov and sidx atoms in that order. Hence for long form content
where the sidx is a non-trivial size, this may result in the
track formats being output a non-negligible period of time
sooner than was previously the case. This allows downstream
renderers to start codec initialization sooner, potentially
decreasing startup latency.
For a single test stream on a fast & stable network, this
pretty consistently reduced elapsed time until both audio and
video codecs have been initialized from ~0.5s to ~0.3 seconds
on a Galaxy S8. For 5 test runs without and with these patches,
the eventTime logged by EventLogger for the second decoder
init were:
Without (secs): 0.47 0.47 0.45 0.48 0.46
With (secs) : 0.32 0.33 0.34 0.31 0.40
PiperOrigin-RevId: 289845089
