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 powerS/N_Y. An upper bound onS/N_Yis found such that source encoding systems will always have values ofS/N_Yless than this bound. The bound has the form (in decibels)S/N_Y ≤ T_B + T_P + T_S, whereT_Bis a constant that depends on the hit rate of the signal,T_Pdepends on the redundancy (or predictability) of the signal, andT_Sdepends 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.