Four channel audio recording in a packet based network
View Patent ↗An apparatus for and a method of audio recording in packet based telephony systems. Using the present invention, the equivalent of four audio channels are recorded utilizing only two recording channels. Each channel recorded comprises the stream of packets generated and transmitted by each endpoint to the other side. The RTP packets include the samples generated by the particular endpoint in addition to the timestamp of the samples received from the other side actually played by the endpoint. The recording device has knowledge of what was played at the other endpoint in order to accurately playback the audio samples generated by and received from the other endpoint. The recording device receives a packet stream containing the audio generated on each endpoint and the timestamp of the packet from the other side that was played on the endpoint. The recording device can reconstruct from this data the audio signal that was actually played on each endpoint.
1. A pseudo four-channel recording method for use in a packet telephony system, said system including a first endpoint, second endpoint and a recording device, said method comprising the steps of:
generating data samples on said first endpoint corresponding to a first audio signal and generating data samples on said second endpoint corresponding to a second audio signal;
tracking a second timestamp of data samples originating from said second endpoint that are played by said first endpoint and tracking a first timestamp of data samples originating from said first endpoint that are played by said second endpoint;
sending a first stream of packets from said first endpoint to said recording device, said first stream of packets containing data samples generated by said first endpoint, a first timestamp corresponding thereto and the second timestamp corresponding to data samples from said second endpoint played by said first endpoint at that moment in time;
sending a second stream of packets from said second endpoint to said recording device, said second stream of packets containing data samples generated by said second endpoint, a second timestamp corresponding thereto and the first timestamp corresponding to data samples from said first endpoint played by said second endpoint at that moment in time; and
recording said first stream of packets and said second stream of packets representing the signals generated and played on said first endpoint and said second endpoint, respectively.
2. The method according to claim 1 , wherein said packets comprise Real-Time Transport Protocol (RTP) packets.
3. The method according to claim 1 , wherein said packet telephony system is constructed in accordance with the International Telecommunications Union (ITU) H.323 protocols.
4. The method according to claim 1 , wherein said packet telephony system is constructed in accordance with the Internet Engineering Task Force (IETF) Session Initiation Protocol (SIP).
5. The method according to claim 1 , further comprising the step of compressing said first stream of packets and said second stream of packets before transmitting them to said recording device.
6. The method according to claim 1 , further comprising the step of decompressing said first stream of packets and said second stream of packets wherein pointer references to data samples are to uncompressed samples.
7. The method according to claim 1 , wherein a timestamp clock rate associated with an endpoint with is greater than or equal to a data sample clock rate.
8. The method according to claim 1 , wherein said first endpoint has knowledge of the sampling rate used by said second endpoint and said second endpoint has knowledge of the sampling rate used by said first endpoint and said recording device has knowledge of sampling rate used by said first endpoint and said second endpoint.
9. The method according to claim 1 , wherein said first timestamp and said second timestamp comprise a packet sequence number and a sample offset within said packet.
10. The method according to claim 1 , further comprising the step of playing back the audio generated on an endpoint utilizing the samples conveyed in a packet stream transmitted to said recording device.
11. The method according to claim 1 , further comprising the step of playing back the audio played on an endpoint utilizing a combination of an indication transmitted from one endpoint and the samples transmitted from another endpoint.
12. The method according to claim 1 , further comprising the step of synchronizing said first packet stream and said second packet stream received by said recording device.
13. A pseudo four-channel recording method for use in a packet telephony system, said system including a first endpoint, second endpoint and a recording device, said method comprising the steps of:
generating data samples on said first endpoint corresponding to a first audio signal and generating data samples on said second endpoint corresponding to a second audio signal;
tracking a second timestamp of data samples originating from said second endpoint that are played by said first endpoint and tracking a first timestamp of data samples originating from said first endpoint that are played by said second endpoint;
recording a first stream of packets at said first endpoint, said first stream of packets containing data samples generated by said first endpoint, a first timestamp corresponding thereto and the second timestamp of data samples from said second endpoint played by said first endpoint at that moment in lime; and
recording a second stream of packets at said second endpoint, said second stream of packets containing data samples generated by said second endpoint, a second timestamp corresponding thereto and the first timestamp of data samples from said first endpoint played by said second endpoint at that moment in time,.
14. The method according to claim 13 , wherein said packets comprise Real-Time Transport Protocol (RTP) packets.
15. The method according to claim 13 , wherein said packet telephony system is constructed in accordance with the International Telecommunications Union (ITU) H.323 protocols.
16. The method according to claim 13 , wherein said packet telephony system is constructed in accordance with the Internet Engineering Task Force (IETF) Session Initiation Protocol (SIP).
17. The method according to claim 13 , further comprising the step of compressing said first stream of packets and said second stream of packets before recording them.
18. The method according to claim 13 , further comprising the step of decompressing said first stream of packets and said second stream of packets wherein pointer references to data samples are to uncompressed samples.
19. The method according to claim 13 , wherein a timestamp clock rate associated with an endpoint with is greater than or equal to a data sample clock rate.
20. The method according to claim 13 , wherein said first endpoint has knowledge of the sampling rate used by said second endpoint and said second endpoint has knowledge of the sampling rate used by said first endpoint.
21. The method according to claim 13 , wherein said first timestamp and said second timestamp comprise a packet sequence number and a sample offset within said packet.
22. The method according to claim 13 , further comprising the step of playing back the audio generated on an endpoint utilizing the samples conveyed in a packet stream transmitted to said recording device.
23. The method according to claim 13 , further comprising the step of playing back the audio played on an endpoint utilizing a combination of an indication transmitted from one endpoint and the samples transmitted from another endpoint.
24. The method according to claim 13 , further comprising the step of collecting and matching call records associated with said first endpoint with call records associated with said second endpoint.
25. The method according to claim 1 , further comprising the step of placing a first indication in said first stream of packets sent to said recording device, said first indication operative to specify whether a packet, several packets, several sequential samples from the same packet or several sequential samples from different packets received by said first endpoint were replayed or that a silence was played.
26. The method according to claim 1 , further comprising the step of placing a second indication in said second stream of packets sent to said recording device, said second indication operative to specify whether a packet, several packet or several sequential samples from the same packet or several sequential samples from different packets received by said second endpoint were replayed or that a silence was played.
27. The method according to claim 13 , further comprising the step of placing a first indication in said first stream of packets operative to specify whether a packet, several packets, several sequential samples from the same packet or several sequential samples from different packets received by said first endpoint were replayed or that a silence was played.
28. The method according to claim 13 , further comprising the step of placing a second indication in said second stream of packets operative to specify whether a packet, several packets, several sequential samples from the same packet or several sequential samples from different packets received by said second endpoint were replayed or that a silence was played.