Audio Basis - articles about audio
Downsampling is a kind of sample rate conversion that is dividing frequency. Sometimes, it's a decimation of samples. Read how to downsampling works.
As rule, downsampling is needed for adapting audio files for available devices and software.
Read also about sound quality optimization for DAC...
You can downsample music with sample rate converter software.
You can downsample music this way:
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How to divide sample frequency (downsampling) two times? Every second sample of the source signal is simply removed.
Alternatively, downsampling may be done via interpolation. It may be done for non-multiple changing of the sample rate.
However, some non-multiple resampling types are provided via multiplying and dividing to integer values.
Read details...
The output spectrum is shown at the bottom of the picture.
The light blue area of the source spectrum is "folded" on the spectrum of audio with a divided sampling rate.
It is non-linear distortions that arise in useful spectrum band after sampling rate dividing.
Spectrum audio after downsampling
On top of the picture, we can see the spectrum of the source audio signal with sampling rate fd. Source signal's spectrum consists of 2 areas (blue and light blue). We see light blue is placed above fd/4.
We divide 2-times the sample rate of source audio and watch to metamorphoses of its spectrum. New sample rate is fd new = fd / 2.
Can this be avoided?
Yes. Before dividing we need to filter (suppress) the source spectrum above fd new / 2 = fd / 4.
About oversampling read here...
Downsampling in audio is reducing of the sampling rate of an audio stream/file. Read more...
Sample rate conversion may affect to sound quality. If the processing is not qualitative, it can cause distortions.
Also, sample rate may impact to playback distortions of a digital-to-analog converter.
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Downsampling loses some information of audio due to lost sampling rate difference. If the target sampling rate is above 44.1 kHz, you can don't worry about the audible range.
A proper resampling tool almost doesn't cause additional losses. Read details...
Downsampling loses sound information and it should degrade the sound.
In the case of a target band of more than 20 kHz, proper downsampling should not cause an audible effect.
But some nuances are there. Read details...
Downsampling may be done in 2 ways: decimation or interpolation.
Read details...