EP0490539A2
Expired / Lapsed
EP
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Adaptive non-linear quantizer
Assignee: AT&T Inc
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Filing: 1991-11-29
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Granted: —
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Expires: 2011-11-29
Abstract
Abstract A quantizer (38), 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 (in 37). 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 (in 49) 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 (in 49). A measure of the fullness of the buffer (56) 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 (38). The scale factors are also applied to the quantizer, as well as a global target distortion measure.
Inventors
- 👤 James David Johnston
- 👤 Scott C. Knauer
- 👤 Kim N. Matthews
- 👤 Arun Narayan Netravali
- 👤 Eric D. Petajan
- 👤 Robert J. Safranek
- 👤 Peter H. Westerink
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 17:42
CPC Classifications
H; H04; H04N; H04N19/00; H04N19/90; H04N19/94; H04N19/10; H04N19/102; H04N19/124; H04N19/126; H04N19/134; H04N19/136; H04N19/137; H04N19/139; H04N19/14; H04N19/154; H04N19/169; H04N19/17; H04N19/172; H04N19/176; H04N19/60; H04N19/61; H04N19/63; H04N19/115; H04N19/146; H04N19/152
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
122 words
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.
Claim 2
Dependent Claim
24 words
The encoder of claim 1 wherein said control signal is further responsive to a selected bit rate target level for said encoder output signals.
Claim 3
Dependent Claim
20 words
The encoder of claim 2 wherein said control signal forms a selected quantization error target for said encoder output signals.
Claim 4
Dependent Claim
20 words
The encoder of claim 1 wherein said selected characteristic is a measure of texture in said applied next frame signals.
Claim 5
Dependent Claim
20 words
The encoder of claim 1 wherein said selected characteristic is a measure of brightness in said applied next frame signals.
Claim 6
Dependent Claim
39 words
The encoder of claim 1 further comprising an output buffer for receiving said encoder output signals, and said coder comprising means for receiving signals from said output buffer that indicate the level of buffer fullness of said output buffer.
Claim 7
Dependent Claim
18 words
The encoder of claim 6 wherein selected characteristic is a measure of buffer fullness of said output buffer.
Claim 8
Dependent Claim
34 words
The encoder of claim 6 wherein selected characteristic is a combination of said buffer fullness of said output buffer, brightness of said applied next frame signals and texture of said applied next frame signals.
Claim 9
Dependent Claim
24 words
The encoder of claim 1 wherein said coder is responsive to applied scale factor signals to control the effective range of said quantizer means.
Claim 10
Dependent Claim
37 words
The encoder of claim 1 further comprising: forward estimation means including means for processing said next frame signals to develop said control signal within a processing interval; and delaying said next frame signals by said processing interval.
Claim 11
Dependent Claim
79 words
The encoder of claim 1 wherein said next frame signals comprise a sequence of signal sections, each of which is related to a transform of at least one block of said frame difference signals, and each of which including a collection of N transform element signals, and said control signal comprising N control signal cells, where N in a constant, and each control signal cell controls the quantization schema for a different one of said N transform element signals.
Claim 12
Dependent Claim
34 words
The encoder of claim 11 wherein said control signal having N control signal cells is a control signal vector that is selected from a look-up table that contains a collection of control signal vectors.
Claim 13
Dependent Claim
52 words
The encoder of claim 12 wherein the selection from said look-up table is based on an error level that is obtained by coder said frame difference signal under control of each vector and said selected characteristic, and by developing a quantization error signal that is subtracted from a quantization error target level.
Claim 14
Dependent Claim
22 words
The encoder of claim 13 wherein said selection is further based on the number of bits created by said coder quantizer means.
Claim 15
Dependent Claim
62 words
The encoder of claim 12 wherein the selection from said look-up table is based on an error level that is obtained by scaling said frame difference signal, coding the scaled frame difference signal under control of each vector and said selected characteristic and by developing a quantization error signal that is subtracted in an absolute sense from a quantization error target level.
Claim 16
Dependent Claim
121 words
An encoder comprising: prediction means responsive to output signals of said encoder, for developing frame prediction signal; 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 codering schemas, where different coder schemas yield different numbers of bits for coded results of equal 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.
Claim 17
Dependent Claim
37 words
The encoder of claim 16 wherein said control means develops a control signal that controls said coder means to develop a number of bits for each frame of said applied frame signals that approaches a preselect number.
Claim 18
Dependent Claim
39 words
The encoder of claim 16 wherein said control means develops a control signal that controls said coder means to develop a number of bits for each frame of said applied frame signals that on average approaches a preselect number.
Claim 19
Dependent Claim
49 words
The encoder of claim 16 where said control means is further responsive to said applied frame signals and modifies its developed control signal based on said applied frame signals to control the coding error signals created in said coder in the course of coding of said frame difference signals.
Claim 20
Dependent Claim
34 words
The encoder of claim 17 where said control means modifies said control signal in response to said applied frame signal to equalize said coding error signals throughout a frame of said applied frame signals.
Claim 21
Dependent Claim
75 words
The encoder of claim 17 where said control means develops said control signal in accordance with a visual perception model for humans, to cause the creation of encoder output signals that, when said encoder output signals are decoded and a frame image is created and displayed, the coding error signals found in said created and displayed frame image are perceived, in accordance with said visual perception model, to be essentially equally visible throughout said frame.
References Cited (Backward Citations)
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