PS3 Upsampling - Linear PCM 7.1 Ch. @ 176.4 kHz

[Clark Kent]

The sound quality of 44.1 kHz digital audio data can be dramatically improved by employing a “poor” oversampling digital anti-imaging filter having a slow roll-off in place of a “good” digital filter having a fast roll-off and a high stop band attenuation. It was shown that the ultrasonic images output by this “poor” filter is responsible for the improved sound quality, reducing certain forms of non-linear distortion such as that due to the differential non-linearity found in all DACs. There may very well be other, subtler, forms of non-linear distortion in DACs, which may also be reduced by signal-dependent ultrasonic dither.

In any case, there are certainly many other sources of non-linear distortion present in the signal chain. Some may question how such a small reduction in non-linear distortion due to differential non-linearity in DACs can be heard when much larger non-linear distortions are generated by loudspeakers, for example. The answer is that the non-linear distortions in question, like jitter-induced non-linearities, are uniquely digital in origin. Such digital distortions have no counterpart in the analog domain. It can be argued that human hearing is much more sensitive to certain digital forms of distortion as compared to the more common distortions of analog origin. For example, it is widely recognized that very low levels of jitter are audible even in the presence of much larger levels of harmonic distortion generated by loudspeakers.