Developing an Asynchronous Sample Rate Converter
Designing an Asynchronous Sample Rate converter that offers high THD and low ripple across a range of frequencies is no mean achievement. We not only designed the ASRC but implemented it with low MHz on a fixed point processor.
Project scope:
Features:
- Any-to-any fixed Sampling Rate Converter (SRC)
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- 48kHz, 44.1kHz, 32kHz, 24kHz, 22.05kHz, 16kHz, 12kHz, 11.025kHz, 8kHz
- Asynchronous SRC
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- From a dynamic input rate to a fixed output rate
- Used with SPDIF input and an external PLL circuit to measure ratio of sampling rates
- Pass-band upto 0.45fs
Performance:
- High quality
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- Low pass band ripple; stop band attenuation upto> 120dB
- THD+N upto> 100dB
- Low MHz
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- < 10 Mhz for 48 à 44.1kHz on RISC CPU
- < 25 MHz for 96 à 44.1kHz on RISC CPU
Highlights:
- Multi-rate signal processing with poly phase filters
- Filter design (FIR filters, IIR filters with near-linear phase)
- Fixed point design for maintaining >100dB SNR
- Highly optimised assembly implementation