Method and apparatus for adjusting dynamic range and gain in an encoder/decoder for multidimensional sound fields

• US 5,633,981 A
• Filed: 06/07/1995
• Issued: 05/27/1997
• Est. Priority Date: 01/08/1991
• Status: Expired due to Term

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Davis, Mark F.
• Primary Examiner(s): MacDonald, Allen R.
• Assistant Examiner(s): Dorvil, Richemond
• Application Number:
  US08/472,231
• Time in Patent Office: 720 Days
• Field of Search: 395/2.14, 395/2.15, 395/234, 395/238, 395/239
• US Class Current: 704/230
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: G11B 20/00 Signal processing not specific to the method of recording or reproducing; Circuits therefor
• CPC Class Codes: G11B 20/10527 Audio or video recording; Data buffering arrangements G11B20/12 - G11B20/18 take precedence
• CPC Class Codes: H04H 20/91 broadcasting computer programmes
• CPC Class Codes: H04S 3/008 in which the audio signals are in digital form, i.e. employing more than two discrete digital channels data reduction aspects thereof based on psychoacoustics G10L19/02

Abstract

An audio encoder/decoder system suitable for digital motion picture film soundtracks provides for adjusting playback signal gain and dynamic range by modifying the scale factors of scaled spectral information. In one embodiment of a transform coding system, transform coefficients are expressed in floating-point form and adjustments are made by modifying the exponents in the floating-point representation.

Claims

1. An encoder for encoding an input signal, said encoder comprising:

subband means for generating subband information for a plurality of subbands in response to said input signal,

means for representing said subband information in floating-point form comprising a plurality of exponents and a plurality of mantissas, each exponent associated with one or more mantissas,

means for generating modified subband information by adjusting either or both dynamic range and gain of said subband information by altering values of one or more of said exponents, and

means for assembling a representation of said modified subband information into a coded signal.

2. An encoder according to claim 1 wherein each of said plurality of subbands has a bandwidth substantially the same or less than that of a respective critical bandwidth of the human auditory system.

3. An encoder according to claim 1 wherein said altering is restricted to exponents of selected ones of said plurality of subbands.

4. A decoder for decoding a coded signal including a representation of subband information for a plurality of subbands of an input signal, said decoder comprising:

means for deriving said subband information from said coded signal and for representing said subband information in floating-point form comprising a plurality of exponents and a plurality of mantissas, each exponent associated with one or more mantissas,

means for generating modified subband information by adjusting either or both dynamic range and gain of said subband information by altering values of one or more of said exponents, and

synthesis means for generating an output signal in response to said modified subband information.

5. A decoder according to claim 4 wherein each of said plurality of subbands has a bandwidth substantially the same or less than that of a respective critical bandwidth of the human auditory system.

6. A decoder according to claim 4 wherein said altering is restricted to exponents of selected ones of said plurality of subbands.

7. A method for encoding an input signal, said method comprising:

generating subband information for a plurality of subbands in response to said input signal,

representing said subband information in floating-point form comprising a plurality of exponents and a plurality of mantissas, each exponent associated with one or more mantissas,

generating modified subband information by adjusting either or both dynamic range and gain of said subband information by altering values of one or more of said exponents, and

assembling a representation of said modified subband information into a coded signal.

8. A method according to claim 7 wherein each of said plurality of subbands has a bandwidth substantially the same or less than that of a respective critical bandwidth of the human auditory system.

9. A method according to claim 7 wherein said altering is restricted to exponents of selected ones of said plurality of subbands.

10. A method for decoding a coded signal including a representation of subband information for a plurality of subbands of an input signal, said method comprising:

deriving said subband information from said coded signal and representing said subband information in floating-point form comprising a plurality of exponents and a plurality of mantissas, each exponent associated with one or more mantissas,

generating modified subband information by adjusting either or both dynamic range and gain of said subband information by altering values of one or more of said exponents, and

generating an output signal in response to said modified subband information.

11. A method according to claim 10 wherein each of said plurality of subbands has a bandwidth substantially the same or less than that of a respective critical bandwidth of the human auditory system.

12. A method according to claim 10 wherein said altering is restricted to exponents of selected ones of said plurality of subbands.