Method and apparatus for analog and digital audio blend for HD radio receivers

1. A method for processing a composite digital radio broadcast signal to smooth signal blending, comprising:

separating a received composite digital radio broadcast signal into an analog audio portion and a digital audio portion;

demodulating the analog audio portion of the composite digital radio broadcast signal to produce analog audio signal samples;

demodulating the digital audio portion of the composite digital radio broadcast signal to produce digital audio signal samples by:

demodulating the digital audio portion of the composite digital radio broadcast signal to produce a digital audio signal,

decoding the digital audio signal using an upper layer decoding process to compute a plurality of compressed audio packets,

processing each compressed audio packet in the compressed audio domain to compute a corresponding digital audio quality indicator value prior to performing audio decoding on said compressed audio packet,

storing each compressed audio packet in an audio blend buffer for storing a plurality of compressed audio packets, and

performing audio decoding on audio information from each compressed audio packet stored in the audio blend buffer with an audio decoder which is connected to an output of the audio blend buffer to generate decompressed digital audio signal samples; and

digitally combining the analog audio signal samples with the digital audio signal samples to produce an audio output by preventing or delaying blending from analog to digital when indicated by one or more corresponding digital audio quality indicator values.

2. The method of claim 1 , where the composite digital radio broadcast signal comprises an over-the-air in-band on-channel digital radio broadcast signal.

3. The method of claim 1 , where demodulating the digital audio portion of the composite digital radio broadcast signal to produce a digital audio signal comprises performing deinterleaving, code combining, forward error correction (FEC) decoding, and error flagging on the digital audio portion of the composite digital radio broadcast signal to produce a baseband digital signal.

4. The method of claim 3 , where decoding the digital audio signal comprises performing audio transport decoding of the digital baseband signal to compute the plurality of compressed audio packets.

5. The method of claim 1 , where processing each compressed audio packet to compute the corresponding digital audio quality indicator value comprises parsing and checking each compressed audio packet for data corruption.

6. The method of claim 1 , where processing each compressed audio packet to compute the corresponding digital audio quality indicator value comprises performing a consistency check for each header on each compressed audio packet.

7. The method of claim 1 , where each compressed audio packet stored in the audio blend buffer is simultaneously processed to compute the corresponding digital audio quality indicator value.

8. The method of claim 1 , where each compressed audio packet is stored in the audio blend buffer after being processed to compute the corresponding digital audio quality indicator value.

9. The method of claim 8 , further comprising storing the corresponding digital audio quality indicator value in a memory storage device comprising:

a look ahead buffer for storing K look ahead digital audio quality indicator values corresponding to K compressed audio packets stored in an audio packet buffer; and

a current buffer for storing M current digital audio quality indicator values corresponding to the plurality of compressed audio packets stored in the audio blend buffer.

10. The method of claim 9 , further comprising:

calculating a future digital audio quality metric based on the K look ahead quality indicator values, and

calculating a current digital audio quality metric based on the M quality indicator values,

where digitally combining the analog audio signal samples with the digital audio signal samples comprises preventing or delaying blending from analog to digital when a current digital audio quality metric has a first value indicating that the compressed audio packets stored in the audio blend buffer are undistorted and a future digital audio quality metric has a second value indicating that future compressed audio packets are distorted.

11. The method of claim 1 , further comprising:

storing supplemental program service (SPS) audio packets in an audio packet buffer; and

storing main program service (MPS) audio packets in the audio blend buffer,

where demodulating the digital audio portion further comprises switching between SPS audio packets and MPS audio packets for input into the audio decoder.

12. A receiver for processing a composite digital radio broadcast signal comprising at least one recordable storage medium having stored thereon executable instructions and data which, when executed by at least one processing device, cause the at least one processing device to demodulate a digital audio portion of the composite digital radio broadcast signal to produce digital audio signal samples by:

demodulating the digital audio portion of the composite digital radio broadcast signal to produce a digital audio signal,

decoding the digital audio signal using an upper layer decoding process to compute a plurality of compressed audio packets,

processing each compressed audio packet to compute a corresponding digital audio quality indicator value prior to performing audio decoding on said compressed audio packet,

storing each compressed audio packet in an input buffer which is connected to provide compressed audio packets for input to an audio decoder, and

performing audio decoding on audio information from each compressed audio packet stored in the input buffer with the audio decoder which generates decompressed digital audio signal samples.

13. The receiver of claim 12 , further comprising:

a digital demodulator for demodulating the digital audio portion of the composite digital radio broadcast signal to produce the digital audio signal,

an audio transport decoder for decoding the digital audio signal using the upper layer decoding process to compute the plurality compressed audio packets,

an audio estimator for processing each compressed audio packet to compute the corresponding digital audio quality indicator value,

an audio blend buffer in the input buffer for storing each compressed audio packet, and

an audio decoder connected to an output of the audio blend buffer for processing audio information from each compressed audio packet stored in the audio blend buffer to generate decompressed digital audio signal samples.

14. The receiver of claim 12 , where the executable instructions and data cause the at least one processing device to process each compressed audio packet to compute a corresponding digital audio quality indicator value by performing a consistency check for each header on each compressed audio packet stored in the input buffer or parsing each compressed audio packet stored in the input buffer to check for data corruption.

15. The receiver of claim 12 , where the input buffer comprises an audio packet buffer connected to an audio blend buffer, and where the executable instructions and data cause the at least one processing device to store each compressed audio packet in the audio blend buffer while simultaneously processing each compressed audio packet to compute a corresponding digital audio quality indicator value.

16. The receiver of claim 12 , where the input buffer comprises an audio packet buffer connected to an audio blend buffer, and where the executable instructions and data cause the at least one processing device to process each compressed audio packet stored in the audio packet buffer to compute a corresponding digital audio quality indicator value before storing said compressed audio packet in the audio blend buffer.

17. The receiver of claim 16 , further comprising:

a look ahead buffer for storing K look ahead digital audio quality indicator values corresponding to K compressed audio packets stored in the audio packet buffer; and

a current buffer for storing M current digital audio quality indicator values corresponding to the plurality of compressed audio packets stored in the audio blend buffer.

18. The receiver of claim 17 , further comprising a quality indicator processing module for calculating a future digital audio quality metric based on the K look ahead quality indicator values to indicate whether indicating future compressed audio packets are distorted, and for calculating a current digital audio quality metric based on the M quality indicator values to indicate whether the compressed audio packets stored in the audio blend buffer are undistorted.

19. The receiver of claim 12 , further comprising a selector switch connected at an input of the audio decoder for switching between (1) supplemental program service (SPS) audio packets stored in an audio packet buffer of the input buffer and (2) main program service (MPS) audio packets stored in an audio blend buffer of the input buffer.

20. A tangible non-transitory computer readable medium comprising computer program instructions adapted to cause a baseband processing system to:

demodulate a digital audio portion of a composite digital radio broadcast signal to produce a digital audio signal;

decode the digital audio signal using an upper layer decoding process to compute a plurality of compressed audio packets;

store each compressed audio packet in an input buffer which is connected to provide compressed audio packets for input to an audio decoder, where the input buffer comprises:

an audio packet buffer for storing K look ahead compressed audio packets, and

an audio blend buffer for storing M current compressed audio packets;

process each compressed audio packet to compute a corresponding digital audio quality indicator value prior to performing audio decoding on said compressed audio packet; and

perform audio decoding on audio information from each compressed audio packet stored in the input buffer with the audio decoder which generates decompressed digital audio signal samples.