Simulink Pro Audio Sample Rate Converter

1) Start R14SP2 MATLAB2) Run script run_this_first These demo models Illustrate audio sample rate conversion of a 48 kHz (DAT sampling rate) input audio signal to a 44.1 kHz (CD sampling rate) output audio signal using a multistage multirate FIR rate conversion approach. Professional digital audio recordings are often recorded with a device such as a Digital Audio Tape (DAT) recorder at a 48 kHz sampling rate. These recordings are then edited and mixed by an audio engineer before they are ready to be transferred to a Compact Disc (CD) recording. CDs use a 44.1 kHz audio sampling rate, which means that the original mixed recording at 48 kHz needs to be resampled down to 44.1 kHz before CD mastering. There are many ways to convert a digital audio stream from 48 kHz to 44.1 kHz. The method illustrated in this demo uses three multirate polyphase FIR rate conversion filters in cascade to achieve the required overall fractional resampling ratio, while preserving the signal integrity Between 0 and 20 kHz. The sequential ratios 5:7, 8:7, and 4:3 are used in the cascaded three-stage Sample Rate Conversion subsystem in the demo model. We obtain these ratios by first noting that the ratio 48:44.1 is equivalent to 160:147. Factoring the latter ratio we get (5*2*2*2*2*2):(7*7*3). Therefore we can use the three sequential ratios 5:7, 8:7, and 4:3 to achieve an overall ratio equivalent to 160:147, or 48:44.1. The original 48 kHz audio stream is first resampled at 7/5 the rate yielding a 67.2 kHz sampled audio stream. The audio stream is then resampled at 7/8 the rate yielding a 58.8 kHz sampled audio stream. Finally, the 58.8 kHz sampled audio stream is resampled at 3/4 the rate yielding the desired 44.1 kHz output.