Transport stream dejitterer

A method of substantially removing jitter from a stream of packets transmitted from a transmission site to a reception site, the method comprising the steps of:

• receiving at an intermediate site a stream of frames, each frame encapsulating a set of packets, wherein selected packets include a timestamp defining a time value for a clock external to the intermediate site;
• de-encapsulating the set of packets from each frame;
• determining whether the set of packets from each frame includes a given selected packet having a timestamp therein;
• responsive to the set of packets including the given selected packet, determining a time offset for the given selected packet, wherein the time offset is based upon the position of the given selected packet within the frame in which the given selected packet was received, and stamping a new time value in the timestamp of the given selected packet, wherein the new time value is defined by subtracting the time offset from the time value for the external clock;
• and
• transmitting the packets from the intermediate site at a predetermined rate.

An apparatus for substantially removing jitter from a stream of packets transmitted from a transmission site to a reception site, the apparatus located at an intermediate site and comprising:

• a buffer having packets of the stream stored therein, wherein selected packets of the stream of packets include a timestamp, each timestamp having a time value from a clock external to the apparatus stamped therein;
• a buffer controller adapted to extract time values from the selected packets and extract packets from the buffer;
• a first locked loop having a first local clock, the first locked loop receiving time values from the buffer controller and locking the first clock thereto, wherein individual time values received by the first local clock are modified by subtracting a clumping error estimate therefrom, the clumping error estimate being based on an average bit rate of the stream of packets;
• a second locked loop having a second local clock, the second locked loop receiving timing information relative to the first local clock and locking the second local clock thereto, wherein the buffer controller receives timing signals from the second local clock and extracts buffered packets at a rate measured relative to the second local clock.

An apparatus for substantially removing jitter from a stream of transport packets transmitted from a transmission site to a reception site, the apparatus located at an intermediate site and comprising:

• an input port adapted to receive a stream of network frames carrying the stream of transport packets;
• a de-encapsulator in communication with the input port adapted to extract the transport packets from the network frames;
• a buffer in communication with the de-encapsulator having transport packets of the stream of transport packets stored therein, wherein selected transport packets include a timestamp, each timestamp having a time value from a clock external to the apparatus stamped therein;
• a first locked loop having a first local clock, wherein the first locked loop receives a time value related to the timestamp of the last buffered selected packet for locking the first local clock thereto;
• a buffer controller in communication with the buffer and the first locked loop, the buffer controller adapted to provide the time value related to the timestamp of the last buffered selected packet to the first locked loop minus a clumping error estimate that is based on an average bit rate of the stream of transport packets and extract packets from the buffer at a predetermined rate on a first-in first-out basis, and wherein the rate of extraction is such that the extracted packets are substantially jitter free;
• and
• a second locked loop in communication with the buffer controller and the first locked loop, the second locked loop having a second local clock, the second locked loop receiving timing information relative to the first local clock and locking the second local clock thereto, wherein the buffer controller receives timing signals from the second local clock and the rate of extraction is measured relative to the second local clock.