Claims
- 1. A method of synchronizing the playback of a digital audio broadcast on a plurality of network output devices by inserting a control track pulse in an audio stream of the digital audio broadcast, comprising:
outputting a first control track pulse as part of an audio signal which has unique identifying characteristics and is regularly occurring; outputting a second control track pulse, consecutive to the first control track pulse, so that the time between the first and second control track pulses must be significantly greater than a latency between sending and receiving devices; and coordinating play of audio at the time of the occurrence of the transmission of the second control track pulse assuring the simultaneous output of the audio signal from multiple devices, the control track pulses having a value unique from any other portion of the audio stream, the digital audio broadcast from multiple receiving devices not presenting to a listener any audible delay or echo effect.
- 2. The method of claim 1, wherein the time between the first and second control track pulses is at least one second.
- 3. The method of claim 2, wherein the time between the first and second control track pulses is at least two seconds.
- 4. The method of claim 2, wherein the time between the first and second control track pulses is two seconds, plus or minus 50 milliseconds.
- 5. The method of claim 1, wherein the control track pulse is a single audio sample of maximum amplitude, while reducing any such naturally occurring value by one, so that the pulse value is unique in the digital stream.
- 6. The method of claim 1, wherein the latency is derived using each of the first and second control track pulses.
- 7. The method of claim 6, wherein a transmitting device sends out the first and second control track pulses and is clocked at a base clock rate.
- 8. The method of claim 7, wherein the latency is derived by enabling a counter from the time one of the first and second control track pulses is sent until the time of its return to the transmitting device, the counter being clocked at one half the base clock rate.
- 9. The method of claim 8, further comprising determining the time drift of a receiving device.
- 10. The method of claim 9, wherein the time drift includes the time for the operating system to respond to a command instruction after the control track pulse has been received by the receiving device.
- 11. The method of claim 1, wherein a transmitting device outputs the audio signal, the receiving devices are all in sync, the transmitting device is not in sync with the receiving devices, and one of the receiving devices generates and outputs the control track pulse.
- 12. The method of claim 1, wherein the audio signal is buffered by a transmitting device and the receiving devices.
- 13. The method of claim 1, wherein the playback of the audio by the receiving devices is manually fine tuned.
- 14. The method of claim 1, wherein global positioning system data is used by at least one of the multiple receiving devices.
- 15. A system for synchronizing audio playback of multiple receiving devices, comprising:
a transmitting device; and two or more receiving devices, wherein the receiving devices are synchronized through at least two of the group consisting of a control track pulse, communication latency, and processing latency.
- 16. The system of claim 15, wherein the system has a time drift detector.
- 17. The system of claim 15, wherein the system has a clock synchronizer.
- 18. The system of claim 15, wherein the system has a latency detector.
- 19. The system of claim 15, wherein the system has manual fine tune control.
- 20. The system of claim 15, wherein the system has a time drift detector, a clock synchronizer, a latency detector, and manual fine tune control.
- 21. The system of claim 15, wherein the receiving devices are synchronized through control track pulses and the communication latency is shorter than the time interval between consecutive control track pulses.
- 22. A system for synchronizing the audio playback of two or more receiving devices, comprising:
means for transmitting consecutive control track pulses in an audio stream; and means for receiving the consecutive control track pulses in the audio stream, the time the means for receiving the control track pulse takes to act upon the audio signal being determined by a communications latency between the transmitting means and the receiving means and a processing latency determined by internal processing by the receiving means.
- 23. The system of claim 22, further comprising means for synchronizing clocks located in the receiving means.
- 24. The system of claim 23, further comprising means for detecting time drift in the receiving means.
- 25. The system of claim 24, further comprising means for manual fine tune control of the receiving means.
Parent Case Info
[0001] This invention references a patent application entitled “A Method of Synchronizing Clocks the Playback of a Digital Audio Broadcast using an Audio Waveform Sample”, Gateway Docket No. 2414, and a patent application entitled “A Method of Manually Fine-Tuning Audio Synchronization of a Home Network”, Gateway Docket No. 2415.