Access time describes the interval between push to talk (PTT) and established voice communications between two communication devices. In voice systems, if a transmitting user speaks during access time the receiving user will not hear the transmitting device.
Indicators such as lights or beeps are used to inform the user that access time has passed and that it is safe to talk without truncation. Access time can be quite long relative to typical conversation. The need for indicators is considered an annoyance. Current buffering schemes eliminate truncated audio at the expense of delay.
This invention provides the means to eliminate truncated audio associated with speech during access time for a communication system whose transmitting devices employ digitally sampled microphone audio.
The invention is described in five steps:
1) Buffer audio after PTT in TX communication equipment.
2) Begin audio playback after channel access is gained.
3) Increase the rate of audio sample playback such that TX buffer is depleted faster than new audio samples are received from microphone A/D.
4) Adjust pitch of increased sample rate according to standard pitch preserving, time compressing algorithm at RX end.
5) Reduce TX sample rate playback to standard rate once TX can operate at normal throughput.
