Ensuring EAS performance in audio signal encoding

1. A method of encoding an ancillary code in broadcast audio data while preserving detectability of an Emergency Alert System (EAS) code therein, comprising the steps of:

encoding the broadcast audio data with an ancillary code having a first magnitude;

providing reference data corresponding to an EAS code;

comparing the reference data with at least a portion of the broadcast audio data to produce a match of the reference data with an EAS code present in the broadcast audio data; and

reducing the first magnitude of the ancillary code in response to the match, such that detectability of the EAS code in the broadcast audio data is preserved.

2. The method according to claim 1 wherein the step of comparing further comprises the step of correlating data points from the broadcast audio data with the reference data to produce a correlation value.

3. The method according to claim 2 further comprising the step of determining whether the correlation value is above a predetermined threshold value to produce the match.

4. The method according to claim 1 wherein the step of comparing further comprises the step of correlating data points from a received signal with the reference data to detect data in the broadcast audio data having a predetermined EAS frequency.

5. The method according to claim 1 wherein the ancillary code comprises a sequence of code symbols each represented as a plurality of substantially single-frequency code components.

6. The method according to claim 1 wherein the monitored EAS code comprises an AFSK code.

7. The method according to claim 1 wherein the reference data has a defined frequency pattern and defined amplitude that correlates to a preamble of the EAS code.

8. The method according to claim 7 wherein the step of comparing further comprises the step of monitoring for the preamble of the EAS code.

9. The method according to claim 1 wherein the first magnitude of the ancillary code is reduced for a predetermined time period.

10. The method according to claim 9 wherein the first magnitude of the ancillary code is restored after the expiration of the predetermined time period.

11. The method according to claim 9 further comprising the step of restarting the predetermined time period each time the EAS code is detected.

12. A method of encoding an ancillary code in media data comprising the steps of:

encoding the media data with a first ancillary code having predetermined code characteristics and a first code detection priority;

providing reference data corresponding to a second ancillary code having a second code detection priority higher than the first code detection priority and present from time to time in the media data;

comparing the reference data with at least a portion of the media data, to produce a match of the reference data with the second ancillary code when present therein; and

modifying at least one of the predetermined characteristics of the first ancillary code in response to the match, to ensure detectability of the second ancillary code in the media data.

13. The method according to claim 12 wherein the reference data corresponds to an Emergency Alert System (EAS) code.

14. The method according to claim 13 wherein the reference data has a defined frequency pattern and defined amplitude that correlates to a preamble of the EAS code.

15. The method according to claim 14 wherein the step of comparing further comprises the step of monitoring for the preamble of the EAS code.

16. A method of encoding an ancillary code in media data comprising the steps of:

encoding the media data with a first ancillary code having predetermined code characteristics and a first code detection priority;

detecting a second ancillary code in or to be included in the media data to produce detection data, the second ancillary code having a second code detection priority higher than the first code detection priority; and

modifying at least one of the predetermined characteristics of the first ancillary code for a predetermined time period in response to the detection data, to ensure detectability of the second ancillary code in the media data during the predetermined time period.

17. The method according to claim 16 further comprising the step of providing reference data corresponding to the second ancillary code.

18. The method according to claim 17 wherein the reference data corresponds to an Emergency Alert System (EAS) code.

19. The method according to claim 18 wherein the reference data has a defined frequency pattern and defined amplitude that correlates to a preamble of the EAS code.

20. The method according to claim 19 wherein the step of detecting further comprises the step of monitoring for the preamble of the EAS code.