Apparatus and method for allocating bits temporaly between frames in a coding system
First Claim
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1. A method for adjusting a target bit rate for a frame, said method comprising the steps of:
- (a) determining a picture quality measure of a current frame for a particular frame type;
(b) determining a picture quality measure for each of a plurality of immediately previous frames corresponding to said frame type of said current frame;
(c) computing an average picture quality measure from said picture quality measures of said plurality of immediately previous frames;
(d) computing a difference between the average picture quality measure and the picture quality measure of said current frame for producing a resultant value;
(e) comparing the resultant value to a threshold value for producing a comparing result; and
(f) adjusting said target bit rate in response to said comparing result.
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Abstract
A method and apparatus for temporally allocating bits between frames in a coding system such that temporal fluctuations are smoothed out. Namely, a picture quality is monitored on a frame by frame basis. An average distortion measure is derived from previous picture frames and that average is compared to the distortion measure of a current frame, where the result is used to effect bit budget allocation for each frame in an input image sequence.
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Citations
21 Claims
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1. A method for adjusting a target bit rate for a frame, said method comprising the steps of:
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(a) determining a picture quality measure of a current frame for a particular frame type;
(b) determining a picture quality measure for each of a plurality of immediately previous frames corresponding to said frame type of said current frame;
(c) computing an average picture quality measure from said picture quality measures of said plurality of immediately previous frames;
(d) computing a difference between the average picture quality measure and the picture quality measure of said current frame for producing a resultant value;
(e) comparing the resultant value to a threshold value for producing a comparing result; and
(f) adjusting said target bit rate in response to said comparing result. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A computer readable medium having stored thereon a plurality of instructions including instructions which, when executed by a processor, causes the processor to perform a method comprising the steps of:
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(a) determining a picture quality measure of a current frame for a particular frame type;
(b) determining a picture quality measure for each of a plurality of immediately previous frames corresponding to said frame type of said current frame;
(c) computing an average picture quality measure from said picture quality measures of said plurality of immediately previous frames;
(d) computing a difference between the average picture quality measure and the picture quality measure of said current frame for producing a resultant value;
(e) comparing the resultant value to a threshold value for producing a comparing result; and
(f) adjusting said target bit rate in response to said comparing result.
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12. Apparatus for encoding an input image sequence having at least one input frame, where said frame is partitioned into at least one block, said apparatus comprising:
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a block motion compensator for computing a motion vector for the block and for generating a predicted image using said motion vector;
a transform module for applying a transformation to a difference signal between the input frame and said predicted image, where said transformation produces a plurality of coefficients;
a quantizer for quantizing said plurality of coefficients with a quantizer scale;
a controller for adjusting a target bit rate for a current frame in response to comparing a difference of a picture quality measure of said current frame and an average picture quality measure of a plurality of immediately previous frames corresponding to a frame type of said current frame to a threshold value; and
a coder for coding said plurality of quantized coefficients. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification