MPEG-4 encoded data is input, and a shape code decoder decodes shape data
contained in the encoded image data to obtain ROI information contained in that
image. The frequency transforms of the decoded image data are computed to generate
transform coefficients. A bit shift unit bit-shifts transform coefficients, corresponding
to the ROI, of the generated transform coefficients, to upper bit planes, stuffs
"0"s in blank fields outside the ROI, which are generated by the bit shift process,
and stuffs audio data from an audio buffer in blank fields within the ROI, which
are generated by the bit shift process.
