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USING AN ULTRASOUND SIGNAL FOR CLOCK AND TIMING SYNCHRONIZATION FOR ACOUSTIC ECHO CANCELLATION WITH MULTIPLE TELECONFERENCE DEVICES IN THE SAME ROOM

IP.com Disclosure Number: IPCOM000247327D
Publication Date: 2016-Aug-24
Document File: 15 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database

Related People

Feng Bao: AUTHOR [+3]

Abstract

A solution is that provides clock and timing synchronization across audio devices using an ultrasound signal and ass a configuration parameter to conference bridges to identify devices in same room. Multiple audio devices can be used in the same conference room with their clock and audio packet timing synchronized to a master device by using an ultrasound signal. Each device can be connected to a digital network directly and without additional delay added to the system.

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using an ultrasound signal for clock and timing synchronization for Acoustic Echo Cancellation with multiple teleconference devices in the same room

AUTHORS:

Feng Bao

Subrahmanyam Kunapuli

Tor Sundsbarm

ABSTRACT

A solution is that provides clock and timing synchronization across audio devices using an ultrasound signal and ass a configuration parameter to conference bridges to identify devices in same room.  Multiple audio devices can be used in the same conference room with their clock and audio packet timing synchronized to a master device by using an ultrasound signal. Each device can be connected to a digital network directly and without additional delay added to the system.

DETAILED DESCRIPTION

In many applications, one teleconference device, such as a phone, is not enough to cover audio for an entire conference room. With advances in technology, laptops, tablets and even smart phones can be used as teleconference devices. However, loud speakers and microphones in these devices have a shorter range than normal teleconference endpoint devices. It will be much more convenient if multiple devices, both conventional conference devices and mobile devices, can be used in the same room, with each of the devices independently connected to a digital network.

With multiple devices in one room, conference bridges should not send a microphone signal from one device to other devices in the room.  Microphones on each device receive sound signals from loud speakers from all devices. Acoustic echo cancellation (AEC) on devices in the same room may not work properly due to the fact that each device has its own audio sampling clock. When each device is independently connected to the digital network, these devices may not receive audio signal packets exactly at the same time due to network jitter. Devices may play out the same audio signal received from remote sides with different delay, and the relative delay between different devices may change over time. To make AEC work properly, sampling clock and playback timing across all devices in the room should be synchronized.

IEEE 1588 and Audio Video Bridging (AVB) standards define hardware and software to accomplish synchronization of audio signals across devices. These features cannot be enabled without adding specialized hardware and software.

Presented herein is a software solution for clock and timing synchronization across audio devices using an ultrasound signal and to add a configuration parameter to conference bridges to identify devices in the same room.

A typical teleconference bridge receives compressed audio signal packets from all audio devices (, … ) through a digital network using the Real-time Transport Protocol (RTP), decodes and mixes them, encodes the mixed signals and sends compressed signal packets to remote devices over network (See Figures 1(a) and 1(b) below). The bridge assumes that no device picks up sound signal from same source as other devices. This is true when there is only...