Method and apparatus for level control in blending an audio signal in an in-band on-channel radio system

Patent metadata

Field	Value
Publication number	US-9755598-B2
Application number	US-201514974809-A
Country	US
Kind code	B2
Filing date	Dec 18, 2015
Priority date	Dec 18, 2015
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

A method for processing a digital audio broadcast signal includes: separating an analog audio portion and a digital audio portion of the digital audio broadcast signal; determining the loudness of the analog audio portion and the digital audio portion over a first short time interval; using the loudness of the analog and digital audio portions to calculate a short term average gain; determining a long term average gain; converting one of the long term average gain or the short term average gain to dB; if an output has been blended to digital, adjusting a digital gain parameter by a preselected increment to produce a digital gain parameter; if an output has not been blended to digital, setting the digital gain parameter to the short term average gain; providing the digital gain parameter to an audio processor; and repeating the above steps using a second short time interval.

First claim

What is claimed is:

1. A method for processing a digital audio broadcast signal, the method comprising:
(a) separating an analog audio portion of the digital audio broadcast signal from a digital audio portion of the digital audio broadcast signal;
(b) determining a loudness of the analog audio portion over a first short time interval;
(c) determining a loudness of the digital audio portion over the first short time interval;
(d) using the loudness of the analog audio portion and the loudness of the digital audio portion to calculate a short term average gain;
(e) determining a long term average gain;
(f) converting one of the long term average gain or the short term average gain to dB and providing the converted average gain to an audio processor;
(g) if an output of a receiver has been blended to digital, adjusting a digital gain parameter toward the long term average gain by a preselected increment to produce an adjusted digital gain parameter;
(h) if the output of the receiver has not been blended to digital, setting the digital gain parameter to the short term average gain;
(i) providing the digital gain parameter adjusted by step (g) or step (h) to the audio processor; and
(j) repeating steps (a) through (i) using a second short time interval.

2. The method of claim 1 , wherein:
the short term average gain is a linear ratio of analog audio power and digital audio power.

3. The method of claim 1 , wherein:
the digital gain parameter is adjusted toward the short term average gain; and
the preselected increment is 1 dB.

4. The method of claim 1 , wherein:
the long term average gain comprises a running average of the short term average gain.

5. The method of claim 1 , wherein:
the long term average gain is determined independently of the short term average gain.

6. The method of claim 1 , wherein:
the long term average gain is converted to dB if a long time interval has been met and the short term average gain is converted to dB if the long time interval has not been met.

7. The method of claim 6 , wherein the long time interval comprises an integer multiple of the short time intervals.

8. The method of claim 6 , wherein:
the short time interval is in a range from 1 to 5 seconds and the long time interval is in a range from 5 to 30 seconds.

9. The method of claim 1 , wherein:
the analog audio portion comprises a stream of samples analog modulated program material; and
the digital audio portion comprises a stream of samples digitally modulated program material.

10. The method of claim 1 , wherein the measurements of the levels of the analog audio portion and the digital audio portion are performed in accordance with the International Telecommunications Union Recommendation (ITU-R) BS.1770 specification.

11. A radio receiver comprising:
processing circuitry configured to: (a) separate an analog audio portion of the digital audio broadcast signal from a digital audio portion of the digital audio broadcast signal; (b) determine a loudness of the analog audio portion over a first short time interval; (c) determine a loudness of the digital audio portion over the first short time interval; (d) use the loudness of the analog audio portion and the loudness of the digital audio portion to calculate a short term average gain; (e) determine a long term average gain; (f) convert one of the long term average gain or the short term average gain to dB and provide the converted average gain to an audio processor; (g) if an output of a receiver has been blended to digital, adjust a digital gain parameter by a preselected increment to produce an adjusted digital gain parameter; (h) if the output of the receiver has not been blended to digital, set the digital gain parameter to the short term average gain; (i) provide the digital gain parameter adjusted by step (g) or step (h) to the audio processor; and (j) repeat steps (a) through (i) using a second short time interval.

12. The radio receiver of claim 11 , wherein:
the short term average gain is a linear ratio of analog audio power and digital audio power.

13. The radio receiver of claim 11 , wherein:
the digital gain parameter is adjusted toward the short term average gain; and
the preselected increment is 1 dB.

14. The radio receiver of claim 11 , wherein:
the long term average gain comprises a running average of the short term average gain.

15. The radio receiver of claim 11 , wherein:
the long term average gain is determined independently of the short term average gain.

16. The radio receiver of claim 11 , wherein:
the long term average gain is converted to dB if a long time interval has been met and the short term average gain is converted to dB if the long time interval has not been met.

17. The radio receiver of claim 16 , wherein the long time interval comprises an integer multiple of the short time intervals.

18. The radio receiver of claim 16 , wherein:
the short time interval is in a range from 1 to 5 seconds and the long time interval is in a range from 5 to 30 seconds.

19. The radio receiver of claim 11 , wherein:
the analog audio portion comprises a stream of samples analog modulated program material; and
the digital audio portion comprises a stream of samples digitally modulated program material.

20. The radio receiver of claim 11 , wherein the measurements of the levels of the analog audio portion and the digital audio portion are performed in accordance with the International Telecommunications Union Recommendation (ITU-R) BS.1770 specification.

Assignees

• Ibiquity Digital Corp

Inventors

• Olochwoszcz Gabriel
• Pahuja Ashwini
• Vincelette Scott

Classifications

• H04H20/47 Primary

  specially adapted for stereophonic broadcast systems · CPC title

• G10L19/167

  Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes · CPC title

• H03G3/3005 Primary

  in amplifiers suitable for low-frequencies, e.g. audio amplifiers (H03G3/32, H03G3/34 take precedence) · CPC title

• H03G3/005

  Control by a pilot signal (H03G3/001 takes precedence) · CPC title

• H04H2201/18

  in band on channel [IBOC] · CPC title