A subjective evaluation of noise-shaping quantization for adaptive intra-/interframe DPCM coding of color television signals

Nonuniform quantizers for just not visible reconstruction errors in an adaptive intra-/interframe DPCM scheme for componentcoded color television signals are presented, both for conventional DPCM and for noise-shaping DPCM. Noise feedback filters that minimize the visibility of reconstruction errors by spectral shaping are designed for Y, R-Y, and B-Y. A closed-form description of the “masking function” is derived which leads to the one-parameter “ 6 quantizer” characteristic. Subjective tests that were carried out to determine visibility thresholds for reconstruction errors for conventional DPCM and for noise shaping DPCM show significant gains by noise shaping. For a transmission rate of around 30 Mbitsls, reconstruction errors are almost always below the visibility threshold if variable length encoding of the prediction error is combined with noise shaping within a 3:l:l system.