How can I write a function about upsampling in DSP

I have an recorded speech signal(.wav) with 8kHZ and 8bits.I want to upsample the signal by 2,and then pass the upsampled signal through a LP filter with having cut-off frequency 4kHz.

Answer 1

[Daniel kiracofe]

resample() work might for you to upsample the data.

Filtering in matlab is a two step process. First, you have to design the filter that you want to use. Then, you use the filter on your data. Assuming your sampling frequency is in the variable Fs, and your desired cutoff frequency is Fc, then the most simple filter command would be these two lines:

[b,a] = butter(1, Fc/Fs); filtered_data = filter(b,a,data);

The variables b and a represent the coefficients of the filter in transfer function format. You can basically ignore those.