You can freely build on How Digital Audio Compression Works

What this patent covers

This patent describes a process to shrink digital audio files by converting sound waves into spectral data using a filter bank. It then quantizes this data, meaning it reduces the precision of less audible sounds while keeping important ones intact. The core mechanism uses an 'optimum encoder' that assigns shorter binary codes to frequently occurring data points and longer codes to rare ones, similar to how Morse code uses shorter signals for common letters. It also uses a clever 'escape' mechanism where values outside a common range are assigned a special identifier, which keeps the lookup tables small and manageable.

What is now free to use

All 0 claims of US 5579430 are in the public domain. Specifically:

The 0 dependent claims add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Does not cover raw, uncompressed audio formats like WAV or AIFF.

• Does not cover non-spectral compression techniques like simple pulse-code modulation (PCM) without the described entropy coding.

• Does not cover hardware-specific playback circuitry or digital-to-analog converters.

• Does not cover loss-less audio compression methods that do not use spectral transformation and quantization.

Who is building on this today

Fraunhofer IIS remains a central player in audio coding, having evolved these techniques into AAC (Advanced Audio Coding) and beyond. Major tech companies like Apple, Google, and Dolby have built their media ecosystems upon the foundation of these spectral compression principles.

Products built on expired version of this technology

How to cite this patent in your documentation

Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV. US Patent 5579430. Digital encoding process. Granted 1996, expired 2015. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.