Method of dynamically adapting the size of a jitter buffer

Abstract

The present invention relates to a receiver system in a communication system supporting packet-based communicatior (e.g., an IP-network), including a receiver, speech decoder (40) and a jitter buffer (20) for handling delay variations in the reception of a speech signal consisting of packets containing frames with encoded speech. A jitter buffer controller (50) is provided for keeping information about the functional size of the jitter buffer (20) and for providing the speech decoder (40) with control information, such that the speech decoder (40), based on that information. provides a dynamic adaptation of the size of the jitter buffer (20) using the received encoded, packetized speech signal. The invention also relates to a method of adapting the functional size of the jitter buffer of a receiver system.

Description

PRIORITY CLAIM [0001] This patent application claims priority to PCT patent application number PCT / SE01 / 01140 filed May 31, 2000.FIELD OF THE INVENTION [0002] The present invention relates, generally, to a receiver system in a communication system supporting packet-based communication of speech and data (e.g., an IP-network). More specifically, the present invention relates to a system comprising a receiver, a speech decoder and a jitter buffer for handling variations in the reception of a speech signal consisting of packets containing frames with encoded speech. BACKGROUND OF THE INVENTION [0003] One area undergoing fast development within telecommunications is voice over IP (VOIP) (e.g., Transmission Control Protocol / Internet Protocol-TCP / IP). Developments in this area initially focused on making phone calls at very low costs. Now, developments within this telecommunications area seem promising for new and different business applications. Because both speech and data use the same ...

AI Technical Summary

Benefits of technology

[0009] Therefore, a receiver, or a receiving module or function within a terminal unit, hereinafter commonly referred to as a receiver system, in a communication system is needed providing efficient handling of the variation in arrival time (i.e., packets that arrive irregularly) between consecutive packets. A receiver system is also needed through which the perceived speech quality will be good—particularly improved over conventional receiving systems. A receiver system is also needed to smooth out delay variations—especially by handling jitter in such a way that the size of the jitter buffer can be adapted in an efficient manner. A receiver system is also needed which contains a jitter buffer adapted to balance the delay at the receiving side while still optimizing packet loss. A receiver system including a jitter buffer is also needed to fulfill any requirements and recommendations relating to regular telephony services, and for which the jitter buffer can adapt in an easy manner.

[0011] Moreover, a system is needed for adapting the functional size of a jitter buffer in a receiver system, within a communication system supporting packet-based communication of speech and data, through which jitter buffer adaptations can be performed in an efficient and easy manner. A system is also needed to smooth out delay variations in the reception of consecutive packets containing speech. Moreover, a system is needed to provide good speech quality while reducing the risk of lost packets. Still further, a system is needed for improved perceived speech quality at the receiver. A system is also needed through which the jitter buffer handling capability, within a receiver system can be improved, facilitated and, particularly, optimized.

[0023] In one embodiment, a system handling delay variations of a jitter buffer in a receiver system in a communication system supporting packet-based communication of speech and data is provided, wherein packets with frames (one or more) of encoded speech are received in the jitter buffer from a transmitting terminal unit at a varying first frequency, and wherein the speech decoder fetches packets from the jitter buffer with a second frequency. The system comprises a jitter buffer controller to dynamically control the second frequency with which the decoder fetches packets from the jitter buffer, such that the size of the jitter buffer can be changed or adapted. The frequency at which fetching of packets is performed is controlled through increasing or decreasing the number of samples / pitch periods / frames contained in a packet, when decoded in the decoder.

[0024] In summary, the present invention provides a number of advantages over conventional systems and methods. With the present invention, receiver systems in a communication system provide for efficiently handling variations in arrival time (i.e. packets that arrive irregularly) between consecutive packets while providing improved perceived speech quality; and provide smoothed out delay variations at the receiver while efficiently adapting the size of the jitter buffer-balancing delays at the receiving side and optimizing packet loss. Other advantages offered by the present invention will be readily appreciated upon reading the below detailed description of the embodiments of the invention.

Problems solved by technology

Due to the nature of such networks, specific technical problems like the loss of packets, delay of packets, and jitter often occur.

If the size of the jitter buffer is too large, the one-way delay from mouth to ear will be too large, and the perceived quality will be degraded.

If the jitter buffer is too small, however, packets delayed more than the size of the jitter buffer will arrive too late for any speech synthesis, and will be seen as lost.

However, the above-mentioned conventional solution statically resets the jitter buffer to a certain level at the beginning of each talk-spurt.

Furthermore, if the jitter buffer size becomes too small, packets will be lost.

Similarly, if the jitter buffer becomes too large, an unnecessary delay is introduced.

In both cases, the perceived speech quality will be affected.

This is undesirable.

Moreover, because the jitter buffer is adapted only when there is a speech silence period, the problems will be even more severe during periods of long speech where no jitter buffer adaptations occur.

Images