A critical evaluation of the Dolby Digital compression algorithm
David Andrew Ingbretsen · Digital Scholarship - UNLV (University of Nevada Reno) · 2019
Dolby Digital, or AC-3, provides for the compression of high-quality audio signals at a bit rate of 384 kbps. for 5.1 audio channels. The purpose of this thesis is to conduct an analysis and evaluation of the AC-3 compression algorithm. The main conclusion is that AC-3 allocates too few bits to the upper frequency ranges. This conclusion is supported by two lines of argument. First, a comparison of the AC-3 perceptual coding model with known facts concerning the masking properties of sound reveals omissions in the AC-3 perceptual model that lead to loss of high frequency resolution. Second, a test program comparing the bit allocation generated by AC-3 with the bit allocation generated by MPEG corroborates the conclusion. A remedy for the high frequency loss problem is put forward.