Saturday, March 23, 2013

How big is the sound of music?

How big is the sound of music?  Lucas Mearian. Computerworld. March 21, 2013. 

Recently audiophiles and musicians have been moving toward master-quality music that's playable from a hard drive. That has led to greater use of lossless file formats. A popular file format, or codec, is the MP3.  This is a compressed file format; it is referred to as "lossy," meaning data is lost in the translation from the original master to the compressed format. Analog audio is recorded by sampling it 44,100 times per second, and then the samples are used to reconstruct the audio signal when playing it back digitally. An uncompressed file on a CD for example, uses 44.1KHz or a 1,411Kbits of data per second (Kbps) while a compressed file may only offer a bit rate of up to 256Kbps, which results in lower quality.  Within file formats, there are many sampling rates or frequencies; the higher the sampling rate, the higher the sound quality.

Uncompressed files are often stored as WAV files (Waveform Audio File Format), which can typically be 10 - 40 times larger than MP3 files.Other lossless formats include FLAC (Free Lossless Audio Codec), AIFF (Audio Interchange File Format) and Apple's ALAC (Apple Lossless Audio Codec). These lossless file formats require less storage space than WAV files. These new lossless formats can save disk space and offer high-fidelity music playback. For example, an album in the WAV format make take up 640 MB of space; the same album would take up about 300 MB in the lossless FLAC format. And lossy MP3 file would take up about 60 MB. It is estimated that CDs only offer about 15% of the data that was in a master sound track; when that CD is further compressed into a lossy MP, even more depth and quality of a recording is lost.

A relatively new high-definition file format, called Direct-Stream Digital (DSD), was created by Sony and Philips.  DSD uses a sample rate of 2.8224MHz or 64 times that of a CD's 41.1KHz.

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