A recent post asking about file zipping made me wonder…does audio compression do the same thing? Is it finding pieces of the sound that are identical and then saving them only once in the MP3 file? It’s one thing to identify patterns in a text file and only save one version of the repeating parts, but somehow that doesn’t seem feasible with audio since things like music have so much complexity.
In: Technology
So you have an audio file, which is a digital sampling of a wave form. Now the human ear is better at hearing lower frequencies (pitch) than higher frequencies. We don’t want to throw out higher frequencies… but we could store higher frequencies at a lower fidelity while keeping high fidelity for the frequencies that your ears are good at hearing.
So what you do is you perform a Fourier Transform. This converts the audio file from a waveform to a bunch of frequencies… all of the information is exactly the same, but the format is different. Now, you can store the low frequencies at a high bitrate and you can also store the high frequencies at a low bitrate… saving lots of space. There’s also a bonus feature that when you’re in frequency space… there’s often a lot of frequencies that are just plain empty… you can throw those ones out entirely.
Then your computer or phone or whatever performs an inverse Fourier Transform which gives it back the original signal, except with a loss of fidelity in those higher frequencies.
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