What do sample rate and bit rate mean in a song? Part 2
The meaning of sampling:
Sound is actually a type of energy wave, so it also has the characteristics of frequency and amplitude, with frequency corresponding to the time axis and amplitude corresponding to the level axis. The wave is infinitely smooth and the chain can be considered to be made up of innumerable points. Since storage space is relatively limited, points in the string must be sampled in the digital encoding process.
The sampling process consists of extracting the frequency value of a certain point. Obviously, the more points that are extracted in one second, the richer the frequency information that can be obtained. To restore the waveform, there must be two sampling points in one vibration. The highest frequency that can be felt is 20kHz.
Therefore, to meet the auditory requirements of the human ear, at least 40k samples per second are required, expressed in 40kHz, and these 40kHz are the sampling frequency. Our common CD has a sample rate of 44.1 kHz.
Video and audio synchronization is very important in the acquisition process, it is not enough to have frequency information, we must also obtain the energy value of this frequency and quantify it to represent the strength of the signal. The number of quantization levels is an integer power of 2, and the sample size of our common CD bit is 16 levels, that is, 2 raised to the fourth power.
Sample size is more difficult to understand than sample rate, because it makes it seem abstract. For example, if a wave is sampled 8 times, the energy values corresponding to the sample points are A1-A8, but we just use a sample size of 2 bits, as a result we can only keep the values of 4 points in A1-A8 and discard the other 4.
If we use the 3bit sample size, all 8 points of information is recorded. The larger the sample rate and sample size values, the closer the recorded waveform is to the original signal.
