Tone blocking using variable delay buffer

• US 5,604,793 A
• Filed: 08/03/1995
• Issued: 02/18/1997
• Est. Priority Date: 08/03/1995
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Dialogic, Inc. (Enghouse Systems Limited)
• Inventors: Lin, Wei, Chitrapu, Prabhakar
• Primary Examiner(s): Brown, Thomas W.
• Assistant Examiner(s): Wolinsky, Scott
• Application Number:
  US08/511,060
• Time in Patent Office: 565 Days
• Field of Search: 379/361, 379/283, 379/233, 379/202, 379/201, 379/351, 379/386, 379/67, 379/88, 379/89, 370/13, 370/110.1, 395/162
• US Class Current: 379/88.09
• CPC Class Codes: H04M 3/56 Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities video conference systems H04N7/15
• CPC Class Codes: H04M 3/568 audio processing specific to telephonic conferencing, e.g. spatial distribution, mixing of participants echo suppression in two-way loud-speaking telephone systems H04M9/02; sound field processing per se H04S7/30
• CPC Class Codes: H04M 9/08 Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic
• CPC Class Codes: H04Q 1/4575 which are transmitted in digital form

Abstract

A tone blocking system for use preferably in conferencing systems in order to prevent control tones from being transmitted to other conferees is disclosed. The buffer length used to process the signal and detect tones is varied, being increased when a tone is suspected to allow for sophisticated tone detection algorithms, and being decreased when silence is present by trimming the silence away. The technique minimizes delay, and its degrading effect on echo, but nonetheless provides for a lengthy buffer required to do reliable tone detection. The invention is applicable to any signal other than tone as well.

Claims

1. A method of processing storage blocks in a buffer comprising the steps of:

storing a received audio signal as a plurality of audio blocks;

setting an inpointer and an outpointer at predetermined ones of said audio blocks, the number of storage blocks between said inpointer and outpointer defining a length L of a delay;

increasing the length of the delay each time an additional new audio block is written in which tone is suspected; and

decreasing the length of the delay each time either (i) an output audio block in which there is speech is read out or (ii) an output audio block in which there is tone is confirmed and then discarded or (iii) an output audio block in which there is silence is read out.

2. The method of claim 1 wherein said step of decreasing the length of the delay includes the step of decreasing the length of the delay by a first amount when tone is confirmed and by a second amount when an output audio block comprising silence is read out, said first amount being greater than said second amount.