Audio codec, digital device and voice processing method

• US 7,619,551 B1
• Filed: 07/29/2008
• Issued: 11/17/2009
• Est. Priority Date: 07/29/2008
• Status: Active Grant

• Current Assignee: Fortemedia, Inc.
• Original Assignee: Fortemedia, Inc.
• Inventors: Wu, Li-Te
• Primary Examiner(s): JEAN PIERRE, PEGUY
• Application Number:
  US12/181,481
• Time in Patent Office: 476 Days
• Field of Search: 341/155, 341/143, 341/141, 381/80, 381/81, 381/123, 704/94
• US Class Current: 341/143
• CPC Class Codes: H04M 1/253 Telephone sets using digital voice transmission
• CPC Class Codes: H04M 1/6008 in the transmitter circuit
• CPC Class Codes: H04M 1/6058 involving the use of a headset accessory device connected to the portable telephone
• CPC Class Codes: H04R 3/00 Circuits for transducers , loudspeakers or microphones

Abstract

An audio codec is provided, comprising an analog to digital converter (ADC) operable to receive an analog input signal for producing a first digital signal, and a first decimator down samples the first digital signal to generate a first intermediate signal. A second decimator receives a second digital signal from a digital microphone and down sample the second digital signal to generate a second intermediate signal. A multiplexer selects either the first intermediate signal or the second intermediate signal as a selected signal based on a control signal. A third decimator down samples the selected signal to generate a down sampled signal. A data formatter produces a digital output signal based on the down sampled signal.

Claims

1. An audio codec, comprising:

an analog to digital converter (ADC), operable to receive an analog input signal for producing a first digital signal;

a first decimator, coupled to the ADC for down sampling the first digital signal to generate a first intermediate signal;

a second decimator, operable to receive a second digital signal from a digital microphone and down sample the second digital signal to generate a second intermediate signal;

a multiplexer, coupled to the first decimator and the second decimator, selecting either the first intermediate signal or the second intermediate signal as a selected signal based on a control signal;

a third decimator, coupled to the multiplexer for down sampling the selected signal to generate a down sampled signal;

a data formatter, coupled to the down sampled signal for producing a digital output signal.

2. The audio codec as claimed in claim 1, further comprising a controller for providing the control signal based on availability of the analog input signal.

3. The audio codec as claimed in claim 1, wherein the ADC is a one-bit delta-sigma modulator that converts the analog input signal into the first digital signal, which is a one-bit Pulse Code Modulation (PCM) data stream of a first clock rate.

4. The audio codec as claimed in claim 1, wherein the ADC is a multi-bit delta-sigma modulator that converts the analog input signal into the first digital signal, which is a multi-bit PCM data stream of a first clock rate.

5. The audio codec as claimed in claim 4, wherein the first decimator is a sinc type decimator that down samples the first digital signal by a first factor to generate the first intermediate signal of a second clock rate.

6. The audio codec as claimed in claim 5, wherein the second digital signal is a one-bit Pulse Density Modulated (PDM) data stream of a third clock rate.

7. The audio codec as claimed in claim 6, wherein the second decimator is a sinc type decimator that down samples the second digital signal by a second factor to generate the second intermediate signal of the second clock rate.

8. The audio codec as claimed in claim 1, wherein the third decimator comprises:

a filter, for performing an anti-aliasing filtration on the selected signal to generate a filtration result; and

a down sampler, coupled to the filter, down-sampling the filtration result by a third factor to generate the down sampled signal of a fourth clock rate.

9. A digital device, comprising:

a digital microphone, for generating a second digital signal from a voice input;

an audio codec, coupled to the digital microphone and attachable to an analog microphone, comprising;

an ADC, for receiving an analog input signal from the analog microphone to produce a first digital signal;

a first decimator, coupled to the ADC for down sampling the first digital signal to generate a first intermediate signal;

a second decimator, coupled to the digital microphone, for down sampling the second digital signal to generate a second intermediate signal;

a multiplexer, coupled to the first decimator and the second decimator, selecting either the first intermediate signal or the second intermediate signal as a selected signal based on a control signal;

a third decimator, coupled to the multiplexer, down sampling the selected signal to generate a down sampled signal;

a data formatter, coupled to the down sampled signal for producing a digital output signal.

10. The digital device as claimed in claim 9, wherein the audio codec further comprises a controller for providing the control signal based on connectivity of the analog microphone.

11. The digital device as claimed in claim 9, wherein the ADC is a one-bit delta-sigma modulator that converts the analog input signal into the first digital signal, which is a one-bit PCM data stream of a first clock rate.

12. The digital device as claimed in claim 9, wherein the ADC is a multi-bit delta-sigma modulator that converts the analog input signal into the first digital signal, which is a multi-bit PCM data stream of a first clock rate.

13. The digital device as claimed in claim 12, wherein the first decimator is a sinc type decimator that down samples the first digital signal by a first factor to generate the first intermediate signal of a second clock rate.

14. The digital device as claimed in claim 13, wherein the second digital signal is a one-bit PDM data stream of a third clock rate.

15. The audio codec as claimed in claim 14, wherein the second decimator is a sinc type decimator that down samples the second digital signal by a second factor to generate the second intermediate signal of the second clock rate.

16. The digital device as claimed in claim 9, wherein the third decimator comprises:

a filter, for performing an anti-aliasing filtration on the selected signal to generate a filtration result; and

a down sampler, coupled to the filter, down-sampling the filtration result by a third factor to generate the down sampled signal of a fourth clock rate.

17. A voice processing method for a digital device comprising a digital microphone, comprising:

performing an first process comprising;

receiving a voice input through an analog microphone to generate an analog input signal;

digitizing the analog input signal to generate a first digital signal;

down sampling the first digital signal to generate a first intermediate signal;

performing a second process comprising;

the digital microphone receiving the voice input to generate a second digital signal;

down sampling the second digital signal to generate a second intermediate signal;

selecting either the first intermediate signal or the second intermediate signal as a selected signal based on a control signal;

down sampling the selected signal to generate a down sampled signal;

performing data formation on the down sampled signal to produce a digital output signal.

18. The voice processing method as claimed in claim 17, further comprising:

detecting whether the analog microphone is attached to the digital device;

wherein;

the first process is performed only when the analog microphone is attached to the digital device; and

the control signal is determined based on the connectivity between the analog microphone and the digital device.

19. The voice processing method as claimed in claim 17, wherein the digitization of analog input signal comprises performing a one-bit delta-sigma modulation on the analog input signal to generate the first digital signal, which is a one-bit PCM data stream of a first clock rate.

20. The voice processing method as claimed in claim 17, wherein the digitization of analog input signal comprises performing a multi-bit delta-sigma modulation on the analog input signal to generate the first digital signal, which is a multi-bit PCM data stream of a first clock rate.

21. The voice processing method as claimed in claim 20, wherein down sampling of the first digital signal comprises performing a sinc type decimation to divide the first clock rate by a first factor to generate the first intermediate signal of a second clock rate.

22. The voice processing method as claimed in claim 21, wherein the second digital signal is a one-bit PDM data stream of a third clock rate.

23. The voice processing method as claimed in claim 22, wherein down sampling of the second digital signal comprises performing a sinc type decimation to divide the third clock rate by a second factor to generate the second intermediate signal of the second clock rate.

24. The voice processing method as claimed in claim 17, wherein down sampling of the selected signal comprises:

performing an anti-aliasing filtration on the selected signal to generate a filtration result; and

down-sampling the filtration result by a third factor to generate the down sampled signal of a fourth clock rate.