The principle of resampling:
Resampling is mainly divided into upsampling and downsampling. In the process of sampling, it is necessary to pay attention to the problem of the sampling rate. It is not possible to change the size of the sampling rate at will. According to the sampling theorem : In the analog/digital signal conversion process, when the sampling frequency fs.max is greater than 2 times the highest frequency fmax in the signal (fs.max>=2fmax), the digital signal after sampling completely retains the information in the original signal, generally In practical applications, the sampling frequency is guaranteed to be 5 to 10 times the highest frequency of the signal; the sampling theorem is also known as the Nyquist theorem. (The sampling theorem is from https://baike.so.com/doc/5633981-5846606.html ), so, be sure to pay special attention to this! ! Sampling frequency: Sampling frequency, also known as sampling speed or sampling rate, defines the number of samples per second that are extracted from a continuous signal to form a discrete signal, and it is expressed in Hertz (Hz). The inverse of the sampling frequency is the sampling period or sampling time, which is the time interval between samples. In layman's terms, the sampling frequency refers to how many signal samples the computer collects per second. Example: Normally, for a phone, the sampling rate is 8000Hz, that is to say, when sampling, it is sampled 8000 times per second, that is, 1/8000th of a second. Upsampling: In the process of sampling, it is usually divided into upsampling and downsampling, and the basis for the distinction is the comparison of the new sampling rate and the original sampling rate when resampling, if it is greater than the original signal, it becomes a Upsampling, if it is smaller than the original signal, is called downsampling. The essence of upsampling is interpolation or interpolation. Downsampling: The size of the new sampling rate is smaller than the size of the original sampling rate.
Method: The interpolation method. When resampling, there are mainly three methods: the nearest neighbor method, the bilinear interpolation method and the cubic convolution interpolation method.