Sampling rate conversion system
View Patent ↗A sampling rate conversion system reduces the signal processing burdens carried by cellular phones, headsets, and other electronic devices. Because the system consumes fewer resources to convert between signal sampling rates, the system may significantly reduce processing time and resource requirements in the device. As a result, the device may instead devote resources to performing other useful tasks, such as interacting with the user through a graphical user interface and performing selected processing tasks.
1. A method of converting an input signal sampling rate to a different output signal sampling rate, comprising:
up-sampling the input signal to obtain an up-sampled signal;
low-pass filtering the up-sampled signal to obtain a first filtered up-sampled signal;
time-delaying the up-sampled signal to obtain a time-delayed up-sampled signal;
low-pass filtering the time-delayed up-sampled signal to obtain a second filtered up-sampled signal;
weighting the first filtered up-sampled signal by a first weight factor to obtain a first weighted signal;
weighting the second filtered up-sampled signal by a second weight factor to obtain a second weighted signal; and
adding the first weighted signal and the second weighted signal to obtain an output signal with a selected output signal sampling rate that differs from the input signal sampling rate.
2. The method of claim 1 , where low-pass filtering the up-sampled signal and low-pass filtering the time-delayed up-sampled signal comprise finite impulse response filtering.
3. The method of claim 1 , where the time-delayed up-sampled signal comprises the up-sampled input signal delayed by one sample period with respect to the up-sampled signal.
4. The method of claim 2 , where low-pass filtering the time-delayed up-sampled signal comprises finite impulse response filtering with a time delayed impulse response.
5. The method of claim 2 , where up-sampling the input signal comprises inserting nulls between signal samples of the input signal.
6. The method of claim 2 , where low-pass filtering the up-sampled signal comprises convolving the input signal with an impulse response of a finite impulse response filter.
7. The method of claim 6 , where low-pass filtering the up-sampled signal further comprises filtering with time-dependent filter coefficients.
8. The method of claim 1 , where the first weight factor and the second weight factor comprise time-dependent weight factors.
9. The method of claim 1 , where the first weight factor and the second weight factor comprise constant factors.
10. The method of claim 1 , where the second weight factor comprises a value of about 1 minus the first weight factor.
11. A signal processing system for converting an input signal sampling rate to a different output signal sampling rate, comprising:
up-sampling logic operable to obtain an up-sampled signal from the input signal;
first low-pass logic operable to filter the up-sampled signal to obtain a first filtered up-sampled signal;
time-delay logic operable to delay the up-sampled signal to obtain a time-delayed up-sampled signal;
second low-pass filtering logic operable to filter the time-delayed up-sampled signal to obtain a second filtered up-sampled signal;
weighting logic operable to apply a first weight factor to the first filtered up-sampled signal to obtain a first weighted signal;
weighting logic operable to apply a second weight factor to the second filtered up-sampled signal to obtain a second weighted signal; and
adder logic operable to add the first weighted signal and the second weighted signal to obtain an output signal with a selected output signal sampling rate that differs from the input signal sampling rate.
12. The system of claim 11 , further comprising down-sampling logic operable to down-sample the output signal to obtain a resultant signal with a resultant signal sampling rate that is different than the selected output signal sampling rate, and where the first weight factor comprises a value dependent on the input signal sampling rate, and the resultant signal sampling rate.
13. The system of claim 12 , where the resultant signal sampling rate comprises a time-dependent resultant signal sampling rate.
14. The system of claim 13 , further comprising a buffer that stores samples of the input signal and of the output signal.
15. The system of claim 14 , where the resultant signal sampling rate comprises a value dependent on a sampling rate correction term.
16. The system of claim 14 , where the buffer comprises a ring buffer.
17. The system of claim 12 , where the resultant signal sampling rate comprises a time-dependent sampling rate.
18. A machine readable medium storing machine executable instructions for a processor in a signal processing system, the instructions comprising:
up-sampling logic operable to obtain an up-sampled signal from the input signal;
first low-pass logic operable to filter the up-sampled signal to obtain a first filtered up-sampled signal;
time-delay logic operable to delay the up-sampled signal to obtain a time-delayed up-sampled signal;
second low-pass filtering logic operable to filter the time-delayed up-sampled signal to obtain a second filtered up-sampled signal;
weighting logic operable to apply a first weight factor to the first filtered up-sampled signal to obtain a first weighted signal;
weighting logic operable to apply a second weight factor to the second filtered up-sampled signal to obtain a second weighted signal;
adder logic operable to add the first weighted signal and the second weighted signal to obtain an output signal with a selected output signal sampling rate that differs from the input signal sampling rate.
19. The machine readable medium of claim 18 , further comprising down-sampling logic operable to down-sample the output signal to obtain a resultant signal with a resultant signal sampling rate that is different than the selected output signal sampling rate, and where the first weight factor comprises a value dependent on the input signal sampling rate, and the resultant signal sampling rate.
20. The machine readable medium of claim 19 , where the resultant signal sampling rate comprises a time-dependent resultant signal sampling rate.