Resolution and sampling frequency
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I want to test what resolution and sampling frequency do to the audio signal by reducing sampling rate and resolution of audio files.
How do I do this?
The information I have gotten is that I should start by reducing sampling rate, since it requires the least programming.
And the follow tips:
matlab example of downsampling:
x_downsamling = x (1: 3: end)% takes out every third sample of x vector.
Remember to low-pass filters before downsampling. Why?
Also remember to change the playback speed when playing the sound.
Bit resolution reduction:
Let's say you have a signal that goes between -1 and 1 y.The floor (y + 1) function will take out an integer that is either 0 or 1 so that it is now reduced to 1 bit resolution.Then remember to scale so that the signal goes between -1 and 1.
For other bite resolutions:
1./N*floor(N.*y+a)-bThen select a, b, N to fit the desired bit resolution ..Feel free to test the function you create on a synthetic signal that goes between -1 and 1. you want a curve that looks like a step.
3 个评论
Walter Roberson
2022-4-29
Use resample() unless you are required to implement the downsampling "manually"
Signal quantization is only directly available to fixed-point objects using the Fixed Point Toolbox. However it is easy enough to use discretize() followed by using the bin number to look up the "representative" value for that bin.
Star Strider
2022-4-29
Slight clarification: There are several functions called resample. (This is likely the one you need.)
Let's say you have a signal that goes between -1 and 1 y.The floor (y + 1) function will take out an integer that is either 0 or 1
y = 1
floor(y+1)
2 is neither 0 nor 1. Saying "either 0 or 1" only holds when that "between -1 and 1" is intended to mean "strictly between" and never equal to the bounds. But in signal processing, it is common to get signals that have elements that are exactly -1 or exactly 1
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