![]() The frequency masking phenomenon is exploited extensively in audio coding. Audio coding can reduce this data rate by a factor of 20 with negligible impact on perceived audio quality. As an example, one minute of DVD-quality audio data requires almost 30MB of space or 3.5Mbps of bandwidth for real-time streaming. Raw audio needs huge space for storage, or equivalently, high bandwidth for streaming. Typical sampling frequencies in high-quality audio are 44.1KHz or 48KHz, although lower sampling frequencies are used for sub-woofer channels. Specifically, we'll take a look at a number of recently discovered techniques such as spectral band replication (SBR), integer MDCT (intMDCT), parametric audio coding, and binaural cue coding (BCC), each of which is enabling new applications and improved quality at lower bit rates.Ī “raw” multichannel digital audio signal consists of sequences of 16-bit samples (one sequence per channel). The main focus of this article is the recent advance in audio coding technology and on-going work in the MPEG audio committee. In this article, I'll briefly cover the principles of audio coding and describe at a high level the popular MPEG audio codecs (MP3, AAC) as well as a few proprietary alternatives. ![]() Audio coding is the art and science of compressing audio signals for efficient storage (small file size) and high-quality streaming (low bandwidth). The terrific popularity of portable multimedia players and Internet media services such as iTunes has generated a lot of interest in audio coding. The best approach depends on your storage, your fidelity needs, and the amount of processing at hand. There's no shortage of methods for compressing digital audio. ![]()
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