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AUTOMATIC GAIN ADJUSTMENT IN BASS MANAGEMENT

IP.com Disclosure Number: IPCOM000021403D
Original Publication Date: 2000-Nov-01
Included in the Prior Art Database: 2004-Jan-16
Document File: 1 page(s) / 58K

Publishing Venue

Sony Technical Digest

Related People

Chinping a. Yang: INVENTOR [+2]

Abstract

In DVD, D TV, and other A/V products, bass management is an important part of audio post processing. For some speaker configurations that lack a subwoofer, the combined low frequency components of the signals in the front and rear left channels, front and rear right channels, center channel, and LFE channel are sent to the two large speakers (see fig. 1). This may cause an overflow in the front channels and generate audible distortions, especially when the LFE signal is large.

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Sony Technical Digest, Volume 3, November 2000, ISSN 1521-5180

AUTOMATIC GAIN ADJUSTMENT IN BASS MANAGEMENT

Invention by:

Chinping a. Yang

Robert Du

In DVD, D TV, and other A/V products, bass management is an important part of audio post processing. For some speaker configurations that lack a subwoofer, the combined low frequency components of the signals in the front and rear left channels, front and rear right channels, center channel, and LFE channel are sent to the two large speakers (see fig. 1). This may cause an overflow in the front channels and generate audible distortions, especially when the LFE signal is large.

This invention describes an automatic gain adjustment scheme that can quickly detect overflow and adjust the gain to prevent audible distortions. In our implementation, we use a 24-bit fixed points DSP with 56-bit ALU registers, but the idea applies to other DSPs with guard bits in ALU. After adding the low frequency component to the front left or right channel, the DSP sets a flag if overflow happens. In theory, the DSP can adjust the gain on the current data, but this may cause iterative processing which results in undesirable and unpredictable real-time computational load. For example, this glitch can occur when the overflow happens and the DSP adjusts the gain downward repeatedly.

The approach used here involves processing one block of data (e.g. 32 samples) at a time, setting a flag if any of the operations in the block cause an overflow. That flag is...