Technique for communicating variable bit rate data over a constant bit rate link
View Patent ↗Variable bit rate information is transmitted across a transmission link ( 20 ) at a constant bit rate by multiplexing individual variable bit rate elementary data streams ( 16 1 and 16 2 ) into a composite data stream ( 18 ) having a constant bit rate. A receiving device ( 22 ) receives the constant bit rate stream but delays processing thereof by an interval typically a fraction of the transmission interval. Following the delay interval, the receiving device processes the data at a rate that is independent of, but typically not greater than, the constant bit rate.
1. A method for communicating variable bit rate information, comprising the steps of:
receiving at a receiving device a composite data stream transmitted across a link at a constant bit rate not less than a highest peak rate of a set of variable bit rate elementary data streams that comprise composite data stream;
delaying processing at the receiving device of the composite data stream by a delay interval; and
processing the composite data stream at the receiving device after said delay interval to synchronize packet decoding at the receiving device with a current system time, the processing occurring at a rate independent of the constant bit rate and including the steps of:
recovering from the composite data stream clock references;
de-multiplexing the composite data stream into constituent elementary data streams;
determining if any elementary data stream has a packet with a time stamp matching the current system time, and if so,
determining whether the packet has a packet decode stamp matching the current system time, and if so, then decoding the packet;
determining if the packet has a presentation time stamp matching the current system time, and if so,
rendering the packet.
2. The method according to claim 1 wherein the processing rate of the receiving device does not exceed the constant bit rate.
3. The method according to claim 1 wherein the delay interval is increased if there exists a period during which the constant bit rate does not exceed a peak receiving device processing rate.
4. The method according to claim 1 wherein the receiving step includes the sub-steps of:
storing successive bytes of the composite data stream in a buffer;
checking whether a prescribed number of bytes have been stored; and
ceasing the storage of bytes once a prescribed number of bytes have been received.
5. The method according to claim 1 wherein the step of rendering the packet includes displaying the packet.
6. The method according to claim 1 wherein the step of rendering the packet includes further processing the packet via a CODEC.
7. A method for communicating variable bit rate information, comprising the steps of:
transmitting a composite data stream across a link at a constant bit rate, not less than a highest peak rate of a set of variable bit rate elementary data streams that comprise composite data stream;
receiving the composite data stream at a receiving device;
delaying processing at the receiving device of the composite data stream by a delay interval; and
processing the composite data stream at the receiving device after said delay interval to synchronize packet decoding at the receiving device with a current system time, the processing occurring at a rate independent of the constant bit rate at which the composite data stream is transmitted and including the steps of:
recovering from the composite data stream clock references;
de-multiplexing the composite data stream into constituent elementary data streams;
determining if any elementary data stream has a packet with a time stamp matching the current system time, and if so,
determining whether the packet has a packet decode stamp matching the current system time, and if so, then decoding the packet;
determining if the packet has a presentation time stamp matching the current system time, and if so,
rendering the packet.
8. The method according to claim 7 wherein the step of transmitting the composite data stream includes the step of multiplexing a plurality of elementary data streams to yield the composite data stream.
9. The method according to claim 7 wherein the processing rate of the receiving device does not exceed the constant bit rate at which the composite data stream is transmitted.
10. The method according to claim 7 wherein the delay interval is increased if there exists a period during which the constant bit rate does not exceed a peak receiving device processing rate.
11. The method according to claim 7 wherein the receiving step includes the sub-steps of:
storing successive bytes of the composite data stream in a buffer;
checking whether a prescribed number of bytes have been stored; and
ceasing the storage of bytes once a prescribed number of bytes have been received.
12. The method according to claim 7 wherein the step of rendering the packet includes displaying the packet.
13. The method according to claim 7 wherein the step of rendering the packet includes further processing the packet via a CODEC.
14. Apparatus for receiving variable bit rate information, comprising:
a receiving device that receives composite data stream transmitted across a link at a constant bit rate not less than a highest peak rate of a set of elementary data streams that comprise composite data stream;
the receiving device having a buffer for storing at least a portion of the composite data stream; and
the receiving device delaying processing the composite data stream by a delay interval; and following the delay interval, the receiving device processing the composite data stream at a rate independent of the constant bit rate to synchronize packet decoding at the receiving device with a current system time, the receiving device processing the data stream by the steps of:
and including the steps of:
recovering from the composite data stream clock references;
de-multiplexing the composite data stream into constituent elementary data streams;
determining if any elementary data stream has a packet with a time stamp matching the current system time, and if so,
determining whether the packet has a packet decode stamp matching the current system time, and if so, then decoding the packet;
determining if the packet has a presentation time stamp marching the current system time, and if so,
rendering the packet.
15. A communications system, comprising:
a transmitter for transmitting a composite data stream across a link at a constant bit rate not less than a highest peak rate of a set of variable bit rate elementary data streams that comprise composite data stream;
a receiving device that receives composite data stream transmitted across a link at a constant bit rate not less than a highest peak rate of a set of elementary data streams that comprise composite data stream;
the receiving device having a buffer for storing at least a portion of the composite data stream; and
the receiving device delaying processing the composite data stream by a delay interval; and following the delay interval, the receiving device processing the composite data stream at a rare independent of the constant bit rare to synchronize packet decoding at the receiving device with a current system time, the receiving device processing the data stream by the steps of:
and including the steps of:
recovering from the composite data stream clock references;
de-multiplexing the composite data stream into constituent elementary data streams;
determining if any elementary data stream has a packet with a time stamp matching the current system time, and if so,
determining whether the packet has a packet decode stamp marching the current system time, and if so, then decoding the packet;
determining if the packet has a presentation time stamp marching the current system time, and if so,
rendering the packet.