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How does audio compression work?

Articles in Computer Software | By August R. Garcia

Published 2 months agoFri, 01 Mar 2019 14:44:55 -0800

How is it that complex audio recordings could be transferred over dial-up connections in the 1990s?

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Digital audio files can easily take massive amounts of space, at least in comparison to simple text files or ASCII characters. Considering the slow internet speeds of the early Internet, how was it that users could download music over the Internet at all?

The Age of MIDI

Typically, humans think of audio files being created through a process along these lines:

  1. Get a microphone
  2. Record some audio in front of it

But, these types of recordings can take an extraordinary amount of data. They have to record every possible frequency that you make, exactly when it was made down to fractions of a second, not to mention the fact that microphones are also capturing background noise as well.

In contrast, early audio recordings were done with Musical Instrument Digital Interface (MIDI) files, which instead generated audio with this general process:

  1. Create a list of notes to play and exactly when to play them
  2. Send the list to the user’s computer
  3. Have the user’s computer read the instructions and play the notes on-the-fly

Through this process, files like this file of The Gambler [similar video] can be stored using substantially less data than if it had been recorded. Conceptually, this concept is similar to sheet music.

Similarly to sheet music, the same composition would sound different if played on different instruments. With this concept in mind, MIDI files could be improved upon through the use of Mod files. These files would audio samples for a desired set of instruments, which could provide additional instructions on how to play the composition.

Recording Live Audio

While there are some high quality MIDI files, there are clearly scenarios where audio recording is needed. How can this audio be compressed to a point where it can reasonably be not only stored, but also transferred over the Internet?

The study of human biology is one substantial factor in the development of compression techniques. For example, while there are many sounds that exist, the range of sounds that humans can hear is generally considered to be 20 Hz to 20 kHz. Sounds outside of this range can be removed from audio files. Further, human hearing is particularly detailed within the range of 100Hz and 4kHz; audio data outside of these ranges can, in general, be removed or dampened with minimal impact on the quality of the audio recording.

Of course, the best audio compression technique depends on your use case. Are you willing to sacrifice audio quality with lossy compression in exchange for the smallest file possible? Or do you want to only remove redundant data, resulting in a larger file compressed using lossless audio compression? Depending on how much audio qualit you're willing to sacrifice, the techniques above can be taken to further extremes to continue to reduce filesize at increasing expense to audio quality.

Download more RAM. 🐏 ⨉ 0 Posted by August R. Garcia 2 months ago 🕓 Posted at 01 March, 2019 14:44 PM PST

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August Garcia is some guy who used to sell Viagra on the Internet. He made this website to LARP as a sysadmin while posting about garbage like user-agent spoofing, spintax, the only good keyboard, virtual assitants from Pakistan, links with the rel="nofollow" attributeproxies, regular expressions, HTML and CSSsin, the developer console, and probably some other trash.

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Relevant video featuring Donkey Kong:

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Edit History

• [2019-03-05 9:52 PST] Louis J. V. Cicalese (2 months ago)
• [2019-03-05 9:52 PST] Louis J. V. Cicalese (2 months ago)
🕓 Posted at 05 March, 2019 09:52 AM PST

I am Louis Cicalese, as they say.

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