Simultaneous viewing and reliable recording of multimedia content over a network

1. A video surveillance system comprising:

a camera generating a video signal at a surveillance location;

an encoder receiving the video signal and generating real-time sequenced packets corresponding to the video signal;

a transmit buffer coupled to the encoder for buffering the sequenced packets;

a transmit controller coupled to the encoder and the transmit buffer, wherein the transmit controller transmits an original packet stream comprising the sequenced packets, and wherein the transmit controller is responsive to retransmission requests to transmit sequenced packets from the transmit buffer as a retransmission stream;

a receive controller at a monitoring location for receiving the original packet stream, wherein the receive controller detects missing packets from the original packet stream and transmits corresponding retransmission requests to the transmit controller for the missing packets;

a packet-based network coupling the transmit and receive controllers;

a decoder responsive to the original packet stream to generate a reproduced video signal for viewing at the monitoring location; and

a recorder for storing recorded video responsive to the original packet stream and the retransmission stream;

wherein the retransmission stream includes sequenced packets that are received too late to be used by the decoder for live reproduction, so that the recorded video provides a higher quality reproduced video signal than the reproduced video signal viewed in real-time at the monitoring location; and

wherein the receive controller detects missing packets according to a loss criteria, wherein the real-time sequenced packets each include a respective sequence number monotonically increasing, and wherein the loss criteria comprises detecting that an expected packet having an expected sequence number following the sequence number of an already received packet has not been received but a subsequent packet has been received having a sequence number greater than the expected sequence number by a predetermined threshold.

2. The system of claim 1 wherein the recorder is coupled to the decoder for replaying the recorded video.

3. The system of claim 1 wherein the packet based network is comprised of a wireless cellular data network.

4. The system of claim 1 wherein the sequenced packets in the original packet stream and the retransmission stream are comprised of real time protocol (RTP) packets.

5. The system of claim 4 wherein the retransmission requests are comprised of negative acknowledgement (NACK) messages.

6. The system of claim 4 wherein the original packet stream and the retransmission stream are sent within the same RTP session using respective synchronization source (SSRC) identifiers.

7. The system of claim 4 wherein the original packet stream and the retransmission stream are sent within different RTP sessions using an identical synchronization source (SSRC) identifier.

8. A method of providing video surveillance of a surveillance location from a monitoring location, comprising the steps of:

generating a video signal from a camera at the surveillance location;

encoding the video signal into real-time sequenced packets;

buffering the sequenced packets in a transmit buffer;

transmitting an original packet stream comprising the sequenced packets from the surveillance location to the monitoring location via a packet-based network;

receiving the original packet stream at the monitoring location and applying a loss criteria to detect when there are missing packets from the original packet stream;

when a missing packet is detected, then transmitting a corresponding retransmission request to the surveillance location;

decoding the original packet stream to generate a reproduced video signal for viewing at the monitoring location; and

recording the original packet stream supplemented by the retransmission stream;

wherein the retransmission stream includes sequenced packets that are received too late to be used by the decoder for live reproduction, so that the recorded video provides a higher quality reproduced video signal than the reproduced video signal viewed in real-time at the monitoring location, wherein the real-time sequenced packets each include a respective sequence number monotonically increasing, and wherein the loss criteria comprises detecting that an expected packet having an expected sequence number following the sequence number of an already received packet has not been received but a subsequent packet has been received having a sequence number greater than the expected sequence number by a predetermined threshold.

9. The method of claim 8 wherein the packet based network is comprised of a wireless cellular data network.

10. The method of claim 8 wherein the sequenced packets in the original packet stream and the retransmission stream are comprised of real time protocol (RTP) packets.

11. The method of claim 10 wherein the retransmission requests are comprised of negative acknowledgement (NACK) messages.

12. The method of claim 10 wherein the original packet stream and the retransmission stream are sent within the same RTP session using respective synchronization source (SSRC) identifiers.

13. The method of claim 10 wherein the original packet stream and the retransmission stream are sent within different RTP sessions using an identical synchronization source (SSRC) identifier.