System and method for low delay, interactive communication using multiple TCP connections and scalable coding
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:
transmit a non-key frame only once over a TCP connection even if receipt of the non-key frame by the receiver is unacknowledged within a pre-determined time period ‘T’, and
discard all non-key frames following the unacknowledged non-key frame until the next available key frame in the audiovisual signal;
wherein the S-IMUX is further configured to:
transmit a key frame over a particular open TCP connection; and
if receipt of the key frame over the particular open TCP connection is not acknowledged within a pre-determined time period ‘T’, transmit 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. 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:
transmitting a non-key frame only once over a TCP connection even if receipt of the non-key frame by the receiver is unacknowledged within a pre-determined time period ‘T’; and,
discarding all non-key frames following the unacknowledged non-key frame until the next available key frame in the audiovisual signal;
wherein scheduling transmission of individual scalable-coded data packets of the audiovisual signal over the plurality of TCP connections further comprises:
transmitting a key frame over a particular open TCP connection; and
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.
3. Non-transitory computer readable media comprising a set of instructions to perform the steps recited in the method claim 2 .