Efficient two-stage asynchronous sample-rate converter

1. A sample-rate converter system, comprising:

a simple asynchronous sample-rate converter having an input and an output; and

a synchronous sample-rate converter having an input and an output, wherein the output of the simple asynchronous sample-rate converter is connected to the input of the synchronous sample-rate converter;

wherein: (1) the synchronous sample-rate converter comprises a full synchronous sample-rate converter; or (2) the simple asynchronous sample-rate converter has an input sample-rate and an output sample-rate, and the ratio of the input sample-rate over the output sample-rate is approximately equal to unity.

2. The system of claim 1 , wherein the synchronous sample-rate converter comprises the full synchronous sample-rate converter.

3. The system of claim 1 , wherein the simple asynchronous sample-rate converter has the input sample-rate and the output sample-rate, and the ratio of the input sample-rate over the output sample-rate is approximately equal to the unity.

4. The system of claim 1 , wherein the simple asynchronous sample-rate converter comprises a sample buffer and a controller.

5. The system of claim 1 , wherein the synchronous sample-rate converter comprises a sample buffer and a controller/calculator.

6. The system of claim 1 , wherein the simple asynchronous sample-rate converter comprises a packet buffer and a controller.

7. The system of claim 1 , wherein the synchronous sample-rate converter comprises a packet buffer and a controller/calculator.

8. A sample-rate converter system, comprising:

a synchronous sample-rate converter having an input and an output; and

a simple asynchronous sample-rate converter having an input and an output, wherein the output of the synchronous sample-rate converter is connected to the input of the simple asynchronous sample-rate converters;

wherein: (1) the synchronous sample-rate converter comprises a full synchronous sample-rate converter; (2) the simple asynchronous sample-rate converter has an input sample-rate and an output sample-rate, and the ratio of the input sample-rate over the output sample-rate is approximately equal to unity; (3) the simple asynchronous sample-rate converter has an input sample-rate and an output sample-rate, and the ratio of the input sample-rate over the output sample-rate is approximately equal to unity; (4) the synchronous sample-rate converter comprises a sample buffer and a controller/calculator; (5) the simple asynchronous sample-rate converter comprises a packet buffer and a controller; or (6) the synchronous sample-rate converter comprises a packet buffer and a controller/calculator.

9. The system of claim 8 , wherein the synchronous sample-rate converter comprises the full synchronous sample-rate converter.

10. The system of claim 8 , wherein the simple asynchronous sample-rate converter has the input sample-rate and the output sample-rate, and the ratio of the input sample-rate over the output sample-rate is approximately equal to the unity.

11. The system of claim 8 , wherein the simple asynchronous sample-rate converter comprises the sample buffer and the controller.

12. The system of claim 8 , wherein the synchronous sample-rate converter comprises the sample buffer and the controller/calculator.

13. The system of claim 8 , wherein the simple asynchronous sample-rate converter comprises the packet buffer and the controller.

14. The system of claim 8 , wherein the synchronous sample-rate converter comprises the packet buffer and the controller/calculator.

15. A method for converting samples at an input sample-rate from a source into an output sample-rate, comprising the steps of:

receiving a plurality of input samples from the source;

converting the plurality of input samples at the input sample-rate to a plurality of intermediate samples at an intermediate sample-rate, wherein the plurality of input samples is converted into the plurality of intermediate samples by inserting a new sample or deleting one of the plurality of input samples, and wherein the ratio of the input sample-rate over the intermediate sample-rate is approximately equal to unity; and

converting the plurality of intermediate samples at the intermediate sample-rate into a plurality of output samples at the output sample-rate, wherein the intermediate sample-rate and the output sample-rate are locked together.

16. The method of claim 15 , further comprising the step of smoothing the samples in close proximity to the inserted or deleted samples.

17. The method of claim 15 , wherein the new sample has the same value as one of the input samples directly adjacent to the new sample.

18. The method of claim 15 , wherein the step of inserting new samples comprises creating new samples using standard curve-fitting techniques.

19. The method of claim 15 , wherein the plurality of intermediate samples is converted into the plurality of output samples using interpolation.

20. The method of claim 15 , wherein the samples are transmitted in packets.

21. A method for converting samples at an input sample-rate from a source into an output sample-rate, comprising the steps of:

receiving a plurality of input samples from the source;

converting the plurality of input samples at the input sample-rate to a plurality of intermediate samples at an intermediate sample-rate, wherein the input sample-rate and the intermediate sample-rate are locked together; and

converting the plurality of intermediate samples at the intermediate sample-rate into a plurality of output samples at the output sample-rate, wherein the plurality of intermediate samples is converted into the plurality of output samples by inserting a new sample or deleting one of the plurality of intermediate samples, and wherein the ratio of the intermediate sample-rate over the output sample-rate is approximately equal to unity.

22. The method of claim 21 , further comprising the step of smoothing the samples in close proximity to the inserted or deleted samples.

23. The method of claim 21 , wherein the new sample has the same value as one of the intermediate samples directly adjacent to the new sample.

24. The method of claim 21 , wherein the step of inserting new samples comprises creating new samples using standard curve-fitting techniques.

25. The method of claim 21 , wherein the plurality of input samples is converted into the plurality of intermediate samples using interpolation.

26. The method of claim 21 , wherein the samples are transmitted in packets.