Adaptive non-linear quantizer
DC CAFCFirst Claim
1. An encoder including a coder for developing encoder output signals from frame difference signals, prediction means responsive to said encoder output signals for predicting a next frame'"'"'s signals, and means for developing said frame difference signals from applied next frame signals of an image frame and from output signals of said prediction means, the improvement comprising:
- said coder including controllable quantizer means that quantizes said difference signals in accordance with a quantization schema that varies with the dictates of a control signal; and
said coder including means, responsive to said applied next frame signals, to develop said control signal, which control signal varies throughout said applied next frame with changes in at least one selected characteristic of said applied next frame signals.
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Abstract
A quantizer, with quantization control that is sensitive to input signal characteristics and to output buffer fullness responds to an input signal that is divided into blocks and DCT transformed. The transformed signal is analyzed to develop a brightness correction and to evaluate the texture of the image and the change in texture in the image. Based on these, and in concert with the human visual perception model, perception threshold signals are created for each subband of the transformed signal. Concurrently, scale factors for each subband of the transformed signal are computed, and a measure of variability in the transformed input signal is calculated. A measure of the fullness of the buffer to which the quantizer sends its encoded results is obtained, and that measure is combined with the calculated signal variability to develop a correction signal. The correction signal modifies the perception threshold signals to develop threshold control signals that are applied to the quantizer. The scale factors are also applied to the quantizer, as well as a global target distortion measure.
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Citations
31 Claims
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1. An encoder including a coder for developing encoder output signals from frame difference signals, prediction means responsive to said encoder output signals for predicting a next frame'"'"'s signals, and means for developing said frame difference signals from applied next frame signals of an image frame and from output signals of said prediction means, the improvement comprising:
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said coder including controllable quantizer means that quantizes said difference signals in accordance with a quantization schema that varies with the dictates of a control signal; and said coder including means, responsive to said applied next frame signals, to develop said control signal, which control signal varies throughout said applied next frame with changes in at least one selected characteristic of said applied next frame signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. An encoder comprising:
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prediction means responsive to output signals of said encoder, for developing frame prediction signals; means for developing frame difference signals in response to said frame prediction means and applied frame signals; coder means, responsive to said frame difference signals and to a control signal, for encoding frame difference signals under direction of said control signal, where said coder means codes different portions of said frame difference signals with different coding schemas, where different coding schemas yield different numbers of bits when coding any given signal, said coder means thereby generates a number of bits when encoding said applied frame signals; and control means for developing said control signal in response to said encoder output signals, to control the number of bits generated by said coder means while encoding said applied frame signals. - View Dependent Claims (27, 28, 29, 30, 31)
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Specification