Systems and methods for fine alignment of analog and digital signal pathways
View Patent ↗Methods and systems lor temporally aligning audio samples of digital and analog portions ol a radio broadcast signal involve receiving a radio broadcast signal having analog and digital portions; separating the analog and digital portions; retrieving a stored first time interval of an approximate time for a sample of the digital portion to travel through a digital signal path in a receiver including a digital demodulator: measuring a second time lor the sample of the digital portion to travel from an input of the digital signal path to an input of the digital demodulator; generating a delay amount by adding the first time to the second time; delaying second audio samples of the digital portion by tho delay amount relative to first audio samples of tho analog portion such that the second audio samples are temporally aligned with the first audio samples; and combining ihe first and second audio samples.
1. A method for temporally aligning audio samples of a digital portion of a radio broadcast signal with audio samples of an analog portion of the radio broadcast signal, the method comprising the steps of:
receiving a radio broadcast signal having an analog portion and a digital portion;
separating the analog portion of the radio broadcast signal from the digital portion of the radio broadcast signal;
producing a first plurality of audio samples representative of the analog portion of the radio broadcast signal;
retrieving from a memory a stored first time interval corresponding to an approximate time for data representing a first sample of the digital portion to travel through a digital signal path in a receiver, wherein the digital signal path includes a digital demodulator;
measuring a second time for data representing the first sample of the digital portion to travel from an input of the digital signal path to an input of the digital demodulator;
generating a delay amount for delaying a second plurality of audio samples relative to the first plurality of audio samples such that the second plurality of audio samples is temporally aligned with the first plurality of audio samples by adding the first time to the second time;
producing the second plurality of audio samples representative of the digital portion of the radio broadcast signal;
delaying the second plurality of audio samples by the delay amount such that the second plurality of audio samples is temporally aligned to within a predetermined amount with the first plurality of audio samples; and
digitally combining the first plurality of audio samples with the second plurality of audio samples to produce a combined audio output.
2. The method of claim 1 further comprising the step of:
determining a third time corresponding to a length of time from when data representing the first sample has reached the input of the digital signal path until a next audio interrupt after the first sample has reached the input of a layer two interface, wherein the audio interrupt corresponds to an initial sample of a full audio frame of decoded analog or digital samples; and
wherein generating the delay amount includes subtracting the third time.
3. The method of claim 1 wherein the radio broadcast signal is an in-band-on-channel digital radio signal.
4. The method of claim 1 wherein the analog signal is a frequency modulated signal.
5. The method of claim 1 wherein the analog signal is an amplitude-modulated signal.
6. The method of claim 1 wherein delaying the second plurality of audio samples comprises adjusting a read pointer in a delay buffer.
7. The method of claim 1 wherein the delay amount is represented by a number of samples.
8. A system for temporally aligning audio samples of a digital portion of a radio broadcast signal with audio samples of an analog portion of the radio broadcast signal comprising:
a processing system; and
a memory coupled to the processing system, wherein the processing system is configured to execute steps comprising:
receiving a radio broadcast signal having an analog portion and a digital portion;
separating the analog portion of the radio broadcast signal from the digital portion of the radio broadcast signal;
producing a first plurality of audio samples representative of the analog portion of the radio broadcast signal;
retrieving from a memory a stored first time interval corresponding to an approximate time for data representing a first sample of the digital portion to travel through a digital signal path in a receiver, wherein the digital signal path includes a digital demodulator;
measuring a second time for data representing the first sample of the digital portion to travel from an input of the digital signal path to an input of the digital demodulator;
generating a delay amount for delaying a second plurality of audio samples relative to the first plurality of audio samples such that the second plurality of audio samples is temporally aligned with the first plurality of audio samples by adding the first time to the second time;
producing the second plurality of audio samples representative of the digital portion of the radio broadcast signal;
delaying the second plurality of audio samples by the delay amount such that the second plurality of audio samples is temporally aligned to within a predetermined amount with the first plurality of audio samples; and
digitally combining the first plurality of audio samples with the second plurality of audio samples to produce a combined audio output.
9. The system of claim 8 further comprising the step of:
determining a third time corresponding to a length of time from when data representing the first sample has reached the input of the digital signal path until a next audio interrupt after the first sample has reached the input of a layer two interface, wherein the audio interrupt corresponds to an initial sample of a full audio frame of decoded analog or digital samples; and
wherein generating the delay amount includes subtracting the third time.
10. The system of claim 8 wherein the radio broadcast signal is an in-band-on-channel digital radio signal.
11. The system of claim 8 wherein the analog signal is a frequency modulated signal.
12. The system of claim 8 wherein the analog signal is an amplitude-modulated signal.
13. The system of claim 8 wherein delaying the second plurality of audio samples comprises adjusting a read pointer in a delay buffer.
14. The system of claim 8 wherein the delay amount is represented by a number of samples.
15. A non-transitory, tangible computer readable medium comprising computer program instructions adapted to cause a processing system to execute steps comprising:
receiving a radio broadcast signal having an analog portion and a digital portion;
separating the analog portion of the radio broadcast signal from the digital portion of the radio broadcast signal;
producing a first plurality of audio samples representative of the analog portion of the radio broadcast signal;
retrieving from a memory a stored first time interval corresponding to an approximate time for data representing a first sample of the digital portion to travel through a digital signal path in a receiver, wherein the digital signal path includes a digital demodulator;
measuring a second time for data representing the first sample of the digital portion to travel from an input of the digital signal path to an input of the digital demodulator;
generating a delay amount for delaying a second plurality of audio samples relative to the first plurality of audio samples such that the second plurality of audio samples is temporally aligned with the first plurality of audio samples by adding the first time to the second time;
producing the second plurality of audio samples representative of the digital portion of the radio broadcast signal;
delaying the second plurality of audio samples by the delay amount such that the second plurality of audio samples is temporally aligned to within a predetermined amount with the first plurality of audio samples; and
digitally combining the first plurality of audio samples with the second plurality of audio samples to produce a combined audio output.
16. The computer readable medium of claim 15 further comprising the step of:
determining a third time corresponding to a length of time from when data representing the first sample has reached the input of the digital signal path until a next audio interrupt after the first sample has reached the input of a layer two interface, wherein the audio interrupt corresponds to an initial sample of a full audio frame of decoded analog or digital samples; and
wherein generating the delay amount includes subtracting the third time.
17. The computer readable medium of claim 15 wherein the radio broadcast signal is an in-band-on-channel digital radio signal.
18. The computer readable medium of claim 15 wherein the analog signal is a frequency modulated signal.
19. The computer readable medium of claim 15 wherein the analog signal is an amplitude-modulated signal.
20. The computer readable medium of claim 15 wherein delaying the second plurality of audio samples comprises adjusting a read pointer in a delay buffer.
21. The computer readable medium of claim 15 wherein the delay amount is represented by a number of samples.