Bounds on subjective performance measures for source encoding systems

Quantizing noise is present whenever analog information is encoded into digital form suitable as an input to any digital system such as a computer or digital transmission line. The subjective impairment caused by this noise is frequently measured by the ratio of signal power to frequency-weighted quantizing noise power
S/N_Y
. An upper bound on
S/N_Y
is found such that source encoding systems will always have values of
S/N_Y
less than this bound. The bound has the form (in decibels)
S/N_Y \leq T_B + T_P + T_S
, where
T_B
is a constant that depends on the hit rate of the signal,
T_P
depends on the redundancy (or predictability) of the signal, and
T_S
depends on subjective considerations (as embodied in a subjectively determined frequency-weighting function). The bound is applied to source encoding systems for speech and television signals. By using the frequency-weighting function, bounds on commonly used measures of subjective impairments are possible.