I’m working with the Push-to-Talk (PTT) framework and observing a consistent delay when starting audio capture.
Scenario:
- A PTT call is already active
- The AVAudioSession is fully configured
- I request beginTransmission on the PTT channel
- I start my Audio Unit for recording (AudioOutputUnitStart)
Observed behavior:
- AudioOutputUnitStart takes ~500 ms
- This happens whether I start the Audio Unit:
- after didBeginTransmission, or
- after AVAudioSession didActivate
Comparison:
- Using the same Audio Unit, same format, and same configuration
- Without the PTT framework, AudioOutputUnitStart takes ~200 ms
Additional notes:
- I am not modifying or reconfiguring AVAudioSession when requesting beginTransmission
- The audio session is already set up when the PTT call starts
- There are no interruptions or route changes at the time of starting the Audio Unit
Impact: This extra latency is significant for Push-to-Talk use cases where fast transmit start is critical.