System and method for low-delay, interactive communication using multiple TCP connections and scalable coding
View Patent ↗Systems and methods for communication of scaleable-coded audiovisual signals over multiple TCP/IP connections are provided. The sender schedules and prioritizes transmission of individual scalable-coded data packets over the plurality of TCP connections according to their relative importance in the scalable coding structure for signal reconstruction quality and according to receiver feedback. Low-latency packet delivery over the multiple TCP/IP connections is maintained by avoiding transmission or retransmission of packets that are less important for reconstructed media quality.
1. An audiovisual communication system including a communication network that uses the IP protocol and has a plurality of TCP connections to carry audiovisual signal data packets between a sender and a receiver, wherein audiovisual signals are scalable-coded by the sender into a set of scalable layers according to a scalable coding structure for transmission over the plurality of TCP connections, and wherein portions of the scalable layers data are designated as key frames, the system comprising:
a Scheduling Inverse Multiplexer (S-IMUX) coupled to the plurality of TCP connections at the sender, wherein the S-IMUX is configured to schedule transmission of individual scalable-coded data packets over the plurality of TCP connections;
a Feedback Multiplexer (F-MUX) coupled to the plurality of TCP connections at the receiver, wherein the F-MUX is configured to reassemble individual scalable-coded data packets received over different TCP connections in a single packet stream for decoding;
wherein the S-IMUX is configured to perform the steps of:
(a) transmitting a key frame over a particular open TCP connection, wherein the key frame is a picture or audio frame for which delivery is necessary in order to ensure an uninterrupted visual experience of media presentation at the receiver; and
(b) if receipt of the key frame over the particular open TCP connection is not acknowledged within a pre-determined time period ‘T’, transmitting the unacknowledged key frame over another open TCP connection,
wherein an open TCP connection is a TCP connection that is currently not waiting for an acknowledgement of the receipt of a previous transmission on the TCP connection.
2. The audiovisual communication system of claim 1 , wherein the S-IMUX is configured to repeat step (b) until either receipt of the key frame is acknowledged on a TCP connection or a pre-determined time period ‘T2’ expires.
3. The audiovisual communication system of claim 2 , wherein the S-IMUX is configured to discard, after receipt of a repeat transmission of the key frame is acknowledged on any of the TCP connections used, all following non-key frames until the next available key frame in the audiovisual signal, and to transmit the next available key frame on an open TCP connection.
4. A method for audiovisual communication over a communication network that uses the IP protocol and has a plurality of TCP connections to carry audiovisual signal data packets between a sender and a receiver, wherein audiovisual signals are scalable-coded by the sender into a set of scalable layers according to a scalable coding structure for transmission over the plurality of TCP connections, and wherein portions of the scalable layers data are designated as key frames, the method comprising:
at the sender, scheduling transmission of individual scalable-coded data packets of the audiovisual signal over the plurality of TCP connections;
at the receiver, reassembling individual scalable-coded data packets received over different TCP connections in a single packet stream for decoding;
wherein scheduling transmission of individual scalable-coded data packets of the audiovisual signal over the plurality of TCP connections comprises:
(a) transmitting a key frame over a particular open TCP connection, wherein the key frame is a picture or audio frame for which delivery is necessary in order to ensure an uninterrupted visual experience of media presentation at the receiver; and
(b) if receipt of the key frame over the particular open TCP connection is not acknowledged within a pre-determined time period ‘T’, transmitting the unacknowledged key frame over another open TCP connection,
wherein an open TCP connection that is a TCP connection that is currently not waiting for an acknowledgement of the receipt of a previous transmission on the TCP connection.
5. The method of claim 4 , wherein scheduling transmission of individual scalable-coded data packets of the audiovisual signal over the plurality of TCP connections comprises repeating step (b) until either receipt of the key frame is acknowledged on a TCP connection or a pre-determined time period ‘T2’ expires.
6. The method of claim 5 , wherein scheduling transmission of individual scalable-coded data packets of the audiovisual signal over the plurality of TCP connections comprises:
after receipt of a repeat transmission of the key frame is acknowledged on any of the TCP connections used, discarding all following non-key frames until the next available key frame in the audiovisual signal; and
transmitting the next available key frame on an open TCP connection.