Streaming normalization

• US 20030059064A1
• Filed: 07/25/2002
• Published: 03/27/2003
• Est. Priority Date: 07/25/2001
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Scarr, Christopher A., Dagani, Gabriel, Kridner, Jason, Millikan, Thomas, Hankins, Timothy C.
• Granted Patent: US 7,343,019 B2
• Time in Patent Office: Days
• US Class Current: 381/107
• CPC Class Codes: H03G 3/002 Control of digital or coded signals H03G3/3089 take precedence

Abstract

A normalization for streaming digital audio signals applies a gain factor according to the maximum sample magnitude in a window of samples and compare the gain factor to prior gain factors to adjust the gain factor for the samples in the window of samples. Adaptation of the gain factor with rapid decreases but slow increases avoids saturation but allows quiet passages.

Claims

1. A method of normalization for a sequence of digital signals, comprising:

(a) finding a first gain factor for a first block of digital signals of a sequence of digital signals;

(b) finding a second gain factor for a second block of digital signals; and

(c) adjusting said second gain factor depending upon said first gain factor.

2. The method of claim 1, wherein:

(a) said adjusting of step (c) of claim 1 (i) decreases said second gain factor when said second gain factor is greater than said first gain factor and (ii) increases said second gain factor when said second gain factor is less than said first gain factor.

3. The method of claim 2, wherein:

(a) said adjusting of step (c) of claim 1 (i) decreases said second gain factor by an amount equal to a first constant multiplied by the difference of said second gain factor minus said first gain factor when said second gain factor is greater than said first gain factor and (ii) increases said second gain factor by an amount equal to a second constant multiplied by the difference of said first gain factor minus said second gain factor when said second gain factor is less than said first gain factor, wherein said first constant is larger than said second constant.

4. The method of claim 1, wherein:

(a) said finding a second gain factor of step (b) of claim 1 uses the maximum digital signal value of the signals in said second block; and

(b) said finding a first gain factor of step (a) of claim 1 uses gain factors of said first block plus other ones of said digital signals in said sequence of digital signals.

5. The method of claim 4, wherein:

(a) said second gain factor is constrained to lie in the range 1.0 to K where K is a constant selected from a range of about 2 to 5.

6. A method of normalization for streaming digital signals, comprising:

(a) inputting a stream of digital signals into a playout buffer;

(b) finding a normalization for an output digital signal from said playout buffer by the steps of;

(i) finding the maximum digital signal magnitude of the digital signals in a sequence of digital signals in said playout buffer with said sequence including said output digital signal, (ii) finding a gain factor for said output digital signal using said maximum digital signal magnitude from (i), (iii) combining said gain factor from (ii) with a second normalization for a second output digital signal from said playout buffer where said second output digital signal preceding said output digital signal in said stream;

(c) outputting said output digital signal from said playout buffer and modifying said output digital signal with said normalization;

(d) repeating steps (b) and (c) for a digital signal following said output digital signal in said stream.

7. The method of claim 6, wherein:

(a) periodically repeating said step (a) of claim 6.

8. The method of claim 6, wherein:

(a) said combining of substep (iii) of step (b) of claim 6 is forming a piecewise linear combination of said second normalization and said gain factor.

9. A receiver for streaming signals, comprising:

(a) a playout buffer to receive input signals;

(b) a normalizer coupled to said playout buffer, said normalizer including a current gain circuit, a memory for a prior normalization, and a combiner circuit for updating a prior normalization with a current gain; and

(c) an output coupled to said playout buffer and said normalizer.