Low bit rate multichannel audio coding methods and apparatus using non-linear adaptive bit allocation

• US 5,737,720 A
• Filed: 10/21/1994
• Issued: 04/07/1998
• Est. Priority Date: 10/26/1993
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Ueno, Masatoshi, Miyamori, Shinji
• Primary Examiner(s): MacDonald, Allen R.
• Assistant Examiner(s): Smits, Talivaldis Ivars
• Application Number:
  US08/327,282
• Time in Patent Office: 1,264 Days
• Field of Search: 352/27, 352/37, 369/85, 395/2.38, 395/2.39
• US Class Current: 704/200.1
• CPC Class Codes: H04B 1/665 using psychoacoustic properties of the ear, e.g. masking effect

Abstract

A low bit rate encoder for compression-encoding digital audio signals of a plurality of channels makes use of both the property of the audio signal and the hearing sense of the human being. The encoder includes: an energy detecting section for detecting energies of the digital audio signals every digital audio signals of the respective channel, a bit allocation amount determining section for determining bit allocation amounts to the respective channels on the basis of the detected result, a compression-encoding section for compression-encoding the digital audio signals on the basis of the bit allocation amounts allocated for every respective channel in accordance with the determined bit allocation amounts, and a multiplexing section for multiplexing the compression-encoded signals every respective channels. The bit allocation amount determining means operates to determine bit allocation amounts so that the relationship between the energy and the bit allocation amount of the digital audio signal represents a non-linear characteristic, such that according as energy of the digital audio signal increases, the bit allocation amount increases as a whole. Thus, redundancy of bit allocation amount in compression-encoding of the multi-channel system is eliminated, and high quality compression encoding/decoding can be realized.

Claims

1. A low bit rate encoder adapted for compression-encoding digital audio signals of a plurality of channels, the low bit rate encoder comprising:

energy detecting means for detecting energies of the digital audio signals of each respective channel;

bit allocation amount determining means for determining bit allocation amounts for the respective channels on the basis of the detected energies;

compression-encoding means for compression-encoding the digital audio signals on the basis of the bit allocation amounts allocated to the respective channels; and

multiplexing means for multiplexing the compression-encoded digital audio signals of the respective channels,

the bit allocation amount determining means operative to determine bit allocation amounts so that the relationship between the energy and the bit allocation amount of the digital audio signals represents a non-linear characteristic based upon human hearing sense such that, as energy of the digital audio signals increases, the bit allocation amounts, as a whole, increase, wherein the non-linear characteristic of the bit allocation amount determining means is approximated by a substantially S-shaped curve, beginning at a low bit allocation amount for a first energy level, increasing to a higher bit allocation amount for a second energy level higher than the first energy level, and decreasing to a bit allocation lower than the higher bit allocation amount for a third energy level higher than the second energy level.

2. A low bit rate encoder adapted for compression-encoding digital audio signals of a plurality of channels, the low bit rate encoder comprising:

energy detecting means for detecting energies of the digital audio signals of each respective channel;

bit allocation amount determining means for determining bit allocation amounts for the respective channels on the basis of the detected energies;

compression-encoding means for compression-encoding the digital audio signals on the basis of the bit allocation amounts allocated to the respective channels; and

multiplexing means for multiplexing the compression-encoded digital audio signals of the respective channels,

the bit allocation amount determining means operative to determine bit allocation amounts so that the relationship between the energy and the bit allocation amount of the digital audio signals represents a non-linear characteristic based upon human hearing sense such that, as energy of the digital audio signals increases, the bit allocation amounts, as a whole, increase, wherein the non-linear characteristic of the bit allocation amount determining means is such that, when energy of the digital audio signal is sufficiently large, the bit allocation amount decreases.

3. A low bit rate encoding method of compression-encoding digital audio signals of a plurality of channels, the method comprising the steps of:

detecting energies of the digital audio signals of each respective channel;

determining bit allocation amounts for the respective channels on the basis of the detected energies;

compression-encoding the digital audio signals on the basis of the bit allocation amounts allocated to the respective channels; and

multiplexing the compression-encoded digital audio signals of the respective channels,

wherein, in the step of determining bit allocation amounts, the relationship between energy and bit allocation amount of the digital audio signals represents a non-linear characteristic based upon human hearing sense such that, as energy of the digital audio signals increases, the bit allocation amounts, as a whole, increase, wherein the non-linear characteristic is approximated by a substantially S-shaped curve, beginning at a low bit allocation amount for a first energy level, increasing to a higher bit allocation amount for a second energy level higher than the first energy level, and decreasing to a bit allocation lower than the higher bit allocation amount for a third energy level higher than the second energy level.

4. A low bit rate encoding method of compression-encoding digital audio signals of a plurality of channels, the method comprising the steps of:

detecting energies of the digital audio signals of each respective channel;

determining bit allocation amounts for the respective channels on the basis of the detected energies;

compression-encoding the digital audio signals on the basis of the bit allocation amounts allocated to the respective channels; and

multiplexing the compression-encoded digital audio signals of the respective channels,

wherein, in the step of determining bit allocation amounts, the relationship between energy and bit allocation amount of the digital audio signals represents a non-linear characteristic based upon human hearing sense such that, as energy of the digital audio signals increases, the bit allocation amounts, as a whole, increase, wherein the non-linear characteristic is such that, when energy of the digital audio signal is sufficiently large, the bit allocation amount decreases.