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A Brief Guide to Audio Codecs

Monday, July 21, 2014

Audio codecs are among the most important innovations affecting the communications and entertainment markets. Digital sound capabilities have facilitated new advances in common analog technologies that have existed for more than a few decades. Originally structured for telephony applications, digital models for audio are so pervasive today. Many of the most popular consumer products rely on digital audio, and more are being introduced almost daily. This brief introduction to digital sound recording will give you some of the basic concepts dealing with compression formats.  

There are many factors that affect sound quality. The similarity between the sound originated by the source and the data stored by the computer, usually known as fidelity, is determined by the sound format and the recording method. Lossy audio compression formats like MP3 degrade the audio quality in an almost imperceptible way because of removed information in the audio data. In spite of this degradation, the most important task is the acquisition of the sound data. The advantage of compressed data over uncompressed data is memory. For example, an Apple Uncompressed AIFF (Audio Interchange File Format) file and a compressed counterpart AAC (Advanced Audio Coding) file can have a ratio of almost 5 to 1 compression. That means a typical AIFF file of 40MB can be compressed down to 8MB depending on sample rate and bit rate.

The 3 Formats of Audio Codecs:

  1. Uncompressed audio formats (often referred to as PCM formats) are just as the name suggests — formats that use no compression. This means all the data is available, at the risk of large file sizes. A .WAV audio file is an example of an uncompressed audio file.
  2. Lossless compression applies compression to an uncompressed audio file, but it doesn't lose information or degrade the quality of the digital audio file. The .WMA audio file format uses lossless compression.
  3. Lossy compression will result in some loss of data as the compression algorithm eliminates redundant or unnecessary information — basically, it tosses out what it sees as irrelevant information. Lossy compression has become popular online because of its small file size, as it is easier to transmit over the Internet. Real Audio and .MP3 files uses a lossy compression.

There are so many audio codecs that fall into above three groups that it really boils down to the application and how the end justifies the means. It really is about fidelity and the determination of what the human ear can tolerate. The applications that drive compression standards are VOIP, security for voice recognition, PC audio, audio streaming, HD audio with resolutions up to 24-bit/192kHz, DVD players and recorders, set top boxes, karaoke machines, and more; the list just goes on.

If you’re wondering which audio codec is best for your application, call Symmetry at (310) 536-6190, or contact us online for guidance. 



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