CD quality

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Contents

Overview

The term "CD Quality" is used to describe a digital recording at a Sample frequency of 44.1kHz and Wordlength of 16 bits.

Related Topics

Quantization

PCM

History

In the early days of digital audio, there were many different systems manufactured by different companies; and computer technology was advancing rapidly. In order to make a viable product for consumer applications, SONY and Phillips worked together to develop Compact Disc technology or the "CD" in the early 1980's. At the time it was decided that, based on the dynamic range of analog recording systems, the theoretical dynamic range of 96dB made 16 bit resolution acceptable for high fidelity applications. A sample frequency of 44.1kHz was adequate to record audio signals up to 20kHz, and worked well with the video systems used to record and edit the digital audio in the process of making the CD master tape.

Basics

As the general public became familiar with digital audio through listening to CD's, the term "CD Quality" was coined to describe a linear PCM digital recording with a sample frequency of 44.1kHz and word length of 16 bits. As other formats such as MP3 came into popular use, the term started being miss-used to describe other formats that were "as-good-as" according to someone (?) For example, to less discriminating listeners an MP3 sounded “as good as” a CD; so the term CD Quality was misused to describe an MP3 file. MP3 is a form of Lossy data compression. It quickly became apparent to professional engineers that 16 bit recordings did not have adequate resolution to capture high quality analog audio, and professional systems evolved to work with 24 bit resolution on input and output and higher resolutions internally (32 -64 bit). Although sample frequencies higher than 44.1 kHz offer advantages during conversion to and from digital audio and in DSP; they are not necessary to increase the accuracy of audio signals. Thus sample rates in the range of 88.2 to 96 kHz offer advantages in conversion over 44.1 or 48 kHz; but sample rates higher than 96kHz do not offer increased accuracy of audio conversion.

Click here for more information on the Optimum Sample Rate for Quality Audio

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