This paper investigates a new coding scheme called Fixed Adaptive DCT (FADCT) coding for use in digital VTRs. FADCT coding satisfies many of the demands unique to VTRs. The image is divided into 8x8-pixel sub-blocks, and a two-dimensional DCT is performed on each sub-block. The quantization scheme is adapted to the input image data, thereby increasing coding efficiency. This scheme is designed, however, to keep the output data rate fixed. The following conclusions were reached on the basis of computer simulations: 1 ) FADCT coding improves the SNR 1 dB to 3 dB as compared to non-adaptive DCT coding. 2) A highquality image with SNR over 40 dB can be obtained at 3 bits/pixel. 3 ) Reallocations of the extra bits from the higher AC energy sub-blocks to the lower AC sub-blocks enable the application of adaptive coding to the digital VTR, with a high tolerance for channel errors.
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