Delaying analog sourced audio in a radio simulcast

• US 8,976,969 B2
• Filed: 06/29/2011
• Issued: 03/10/2015
• Est. Priority Date: 06/29/2011
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Elenes, Javier, Taipale, Dana, Anderton, Dave
• Primary Examiner(s): Goins, Davetta W
• Assistant Examiner(s): Ojo, Oyesola C
• Application Number:
  US13/172,208
• Publication Number:
  US 20130003801A1
• Time in Patent Office: 1,350 Days
• Field of Search: 381/2, 455/503, 455/243.1, 455/244, 375/224, 375/254, 375/316, 370/429, 370/487
• US Class Current: 381/2
• CPC Class Codes: H04H 2201/18 in band on channel [IBOC]
• CPC Class Codes: H04H 40/18 Arrangements characterised by circuits or components specially adapted for receiving

Abstract

A method and apparatus is disclosed in which delay is applied to analog-sourced audio in a radio simulcast when the analog signal initially leads the digital signal. A radio receiver is configured to receive a simulcast radio program broadcast with an analog signal and a digital signal. The program content can be extracted from either the analog or digital signals, with the audio source eventually being blended to the digital signal. Audio is initially provided based on the analog signal. If the analog signal is initially leading the digital signal, delay is applied a data stream corresponding to the analog signal relative to a data stream corresponding to the digital signal. Delay applied to the data stream corresponding to the analog signal is increased at a rate that avoids audio artifacts of the output audio. The blend is performed when the data streams are aligned in time.

Claims

1. An apparatus comprising:

a delay unit implemented in a radio receiver, wherein the delay unit is configured to receive a first data stream and a second data stream corresponding respectively to analog-transmitted and digitally-transmitted portions of a simulcast radio program, wherein the delay unit is further configured to determine an amount of an initial time lag between corresponding points of the first data stream and the second data stream;

wherein the delay unit, in response to determining that the second data stream lags the first data stream, is configured to increase an amount of delay applied to the first data stream until the first and second data streams reach a target time alignment, and wherein the delay unit is configured to increase the amount of delay at a rate that avoids audible artifacts in an audio output signal generated from the analog-transmitted portion of the radio program, and wherein the delay unit is further configured to store information indicative of the amount of the initial time lag between the first data stream and the second data stream and further configured to use the recorded initial time lag to re-tune the radio receiver to a source of the simulcast radio program.

2. The apparatus as recited in claim 1, wherein the delay unit is configured to incrementally increase the amount of delay applied to the first data stream.

3. The apparatus as recited in claim 2, wherein the rate is less than or equal to 20 milliseconds per second of audio.

4. The apparatus as recited in claim 1, wherein the delay unit is configured to change the delay by causing a change of a sampling rate of the first data stream.

5. The apparatus as recited in claim 1, wherein the delay unit is configured to change the amount of delay by changing a separation difference between a read pointer and a write pointer of a first-in first-out memory (FIFO).

6. The apparatus as recited in claim 1, further comprising a blend unit, wherein the blend unit is coupled to receive the first data stream and the second data stream, wherein the blend unit is configured to initially produce audio output exclusively from the first data stream, and wherein the blend unit is further configured to subsequently produce audio output exclusively from the second data stream in response to reaching the target time alignment.

7. The apparatus as recited in claim 6, wherein the blend unit is configured to:

transition from outputting only the first data stream for audio playback to outputting only the second data stream for audio playback, wherein said transitioning comprises reducing a first variable signal strength of audio sourced from the first data stream and correspondingly increasing a second variable signal strength of audio sourced from the second data stream.

8. A method comprising:

a delay unit of a radio receiver estimating a reception delay between corresponding points in first and second data streams extracted from analog and digital portions of a radio program, respectively;

in response to determining from the estimated reception delay that the first data stream leads the second data stream, the delay unit changing an internal delay on the first data stream from the estimated reception delay to a target delay at a rate that avoids audible artifacts;

storing in a memory information indicative of an initial value of the estimated reception delay; and

re-tuning the radio receiver to a source of the radio program using the information indicative of the initial value of the estimated reception delay.

9. The method as recited in claim 8, further comprising a blend unit blending from the first data stream to the second data stream.

10. The method as recited in claim 9, wherein blending from the first data stream to the second data stream comprises:

transitioning from outputting only the first data stream for audio playback to outputting only the second data stream for audio playback, wherein said transitioning comprises reducing a first variable signal strength of audio sourced from the first data stream and correspondingly increasing a second variable signal strength of audio sourced from the second data stream.

11. The method as recited in claim 8, further comprising changing the internal delay of the first data stream incrementally.

12. The method as recited in claim 11, further comprising increasing the internal delay of the first data stream by a rate less than or equal to 20 milliseconds per second of audio until the target delay is reached.

13. The method as recited in claim 8, further comprising the delay unit causing the internal delay to change by causing a sample rate converter to change a rate at which the first data stream is sampled.

14. The method as recited in claim 8, further comprising the delay unit causing the internal delay to change by changing a separation of a read pointer and a write pointer of a first-in first-out memory coupled to receive the first data stream.

15. A method, comprising:

a radio receiver receiving a radio program that includes content broadcast as an analog radio signal and the content broadcast as a digital radio signal;

the radio receiver generating a first data stream from the analog radio signal and a second data stream from the digital radio signal;

the radio receiver estimating a reception delay between corresponding points of the first and second data streams;

in response to estimated reception delay indicating that the first data stream leads the second data stream, the radio receiver changing an internal delay of the first data stream to a target delay at a rate that avoids audible artifacts in an audio output of the radio receiver;

storing information indicative of an initial value of the reception delay in a memory; and

re-tuning the radio receiver to a source of the radio program using the information indicative of the initial value of the reception delay.

16. The method as recited in claim 15, further comprising:

the radio receiver initiating a blend operation in response to the internal delay reaching the target delay, wherein the blend operation includes gradually transitioning from generating the audio output based exclusively on the first data stream to generating the audio output based exclusively on the second data stream.

17. The method as recited in claim 15, further comprising changing the internal delay of the first data stream in increments.