US 5,790,538 A · System and method for voice Playout in an asynchronous packet network

Abstract

A System for Voice Playout in an Unsynchronized Packet Network for use with isochronous and asynchronous data transmission over a communication network having at least one receiving unit and at least one transmitting unit each having independent clocks. A FIFO voice codeword storing device in the receiving unit removes timing jitter from incoming packets--and receives voice packets from a data network. A phase continuous packet clock thereafter removes packets from the FIFO voice codeword storing device which is synchronized to the incoming data rate using the fill status of the FIFO voice codeword storing device as a frequency control signal. A continuous phase resampler removes timing frequency offset without causing packet slips or loss of data. The transmitter inserts the contents of a free running packet counter into each transmitted packet, allowing the receiver to detect lost packets and to properly reproduce silence intervals during Playout. A receive sequence counter increments at the local packet rate to schedule Playouts for multiple voice segments. A clock frequency recovery is utilized where the receiver clock frequency differs from the transmitter clock frequency. When the receive clock is not available, such as voice over packet networks applications, the FIFO voice codeword storing device fill status can control the resampling rate.

Claims20

Dependent claims

A System for Voice Playout in an Asynchronous Packet Network comprising:

(a) a transmitting unit comprising a transmitting clock;
(b) a receiving unit comprising a receiving clock and a FIFO voice codeword storing device having a fill status;
and
(c) an incoming packet sequence stream comprising the fill status of said FIFO voice codeword storing device which is transmitted from said transmitting unit to said receiving unit, wherein said incoming packet sequence stream synchronizes said transmitting unit's transmitting clock with said receiving unit's receiving clock by detecting said fill status.

1 more element

A method of transmitting and recovering data in a System for Voice Playout in an Asynchronous Packet Network comprising:

(a) inserting a sequence scheme into incoming packet sequence streams, wherein said incoming packet sequence streams have an incoming data rate;
(b) transmitting said incoming packet sequence streams from a transmitting unit;
(c) receiving said incoming packet sequence streams into a receiving unit;
(d) analyzing said incoming packet sequence streams in said receiving unit;
(e) removing timing jitter from said incoming packet sequence streams;
(f) synchronizing said incoming packet sequence streams received in said receiving unit with said incoming packet sequence streams that were transmitted from said transmitting unit by using the fill status of a FIFO voice codeword storing device;
and
(g) playing said synchronized incoming packet sequence streams at playout.

5 more elements

Dependencies are inferred from the claim text.

System and method for voice Playout in an asynchronous packet network

Life of this patent

System and method for voice Playout in an asynchronous packet network

Life of this patent

Abstract

Claims20