V6 User Manual 1.00.book - Studio General

DitherWhenever changes are made to digital audio signals such as mixing, altering gain, eq or reverb, the result is usuallyan increase in the number of bits. These extra bits have to be removed to suit the requirements of delivery andinterconnect standards. If the bit depth is reduced by simply ignoring the extra bits (truncation) or even roundingthe least significant bit up or down, the resulting error can give rise to audible distortion of low signal levels. Obviously,there is also a permanent loss of resolution. These effects are cumulative. I.e. If the signal is repeatedly processedand bit reduced to shorter word lengths, there will be a significant and audible loss of accuracy in subtle,low level sounds. Human hearing makes use of this low level information in imaging and unless something isdone to avoid the problem, space and clarity will be adversely affected.In Pyramix all processing takes place in 32 bit floating point so, if signals are kept within this environment, there isno need for bit depth reduction until the final stage before output. Truncation or rounding are undesirable but asingle ‘dithering’ stage can reduce bit depth whilst maintaining low level linearity. This is achieved by adding acontrolled amount of low level noise to the signal. Since there is no such thing as a free lunch, the trade off is aslightly increased level of noise. However, the noise can be ‘shaped’ to reduce its perceived audibility.See also: Dithering Options on page 188It is important dithering is only applied once.Project Processes : Dither 16 - 292