Downsampling Audio, Decimation [Explained]
Downsampling is kind of sample rate conversion - dividing frequency (decimation of samples). Read how to work downsampling.
Author: audio software developer Yuri Korzunov.
HD audio file conversion
How to work downsampling
How to divide sample frequency (downsampling) two times? Every second sample of source signal is simply removed.
Sound quality
Output spectrum we see on bottom of the picture. Light blue area of source spectrum mirrored on spectrum of audio with divided sampling rate. It is non-linear distortions arose in useful spectrum band after dividing sampling rate.
Spectrum audio after downsampling
On top of the picture we see spectrum of source audio signal with sampling rate Fd. Spectrum on probation contains 2 areas (blue and light blue). We see what light blue placed above Fd/4.
We will decrease (divide 2 times) sample rate source audio and watch to metamorphoses of its spectrum. New sample rate is Fd new = Fd / 2.
Possible avoid it?
Yes. Before dividing need filter (suppress) source spectrum above Fd new / 2 = Fd / 4.
About oversampling read here...
Read about sample rate issues
- Audio Sample Rate Converter >
- Oversampling >
- DSF oversampling. D64 vs. D128 >
- What Better Multiple or Non-Multiple Resampling >
- Multiple vs. Non-Multiple Resampling Audio [2017] >
- Would need sample rates 352 and 384 kHz >