Lossless conversion between sigma-delta and PCM converters for digital audio applications, with human audible range analysis.

摘要

Pulse Code Modulation (PCM) has been the dominant format for signal representation since the early days of digital audio. This has come about because the compact disc (CD) uses PCM to encode audio. Recently, two high-resolution audio encoding formats have emerged and attempt to replace the CD as the dominant digital audio medium, DVD-Audio and SACD. DVD-A continues the CD tradition by using the same PCM digital audio technology, albeit with improved resolution. The other medium, SACD, encodes the signal in a one-bit format publicly named DSD. Presently, the technique used to encode the signal in DSD is based on Sigma-Delta Modulation (SDM). While both formats offer increased resolution over CD, the argument over which format is better is yet to be resolved at this point. Also, it remains unclear if conversions between these formats cause any audible effect. If an audibly lossless conversion between formats is possible, the argument over which is better would be mute. The thesis of this work is to try to answer these questions, in an attempt to perform lossless conversions between signals modulated in PCM and SDM. Conversions were made using lossless and lossy techniques. Lossless techniques proved unsuitable for audio applications and one-bit signal reconstruction. Lossy techniques were studied using both typical audio signal analysis and listening tests. The listening tests verified that conversions between both formats are indeed audibly lossless. The listening tests also determined the high-resolution formats do not offer significant audible improvements over CD quality. These results lead to the conclusion that current high-resolution formats surpass human audible perception and offer higher quality representation than the accompanying analog hardware in the audio chain.