EP0660612A2
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EP
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Image encoding apparatus
Assignee: Sharp Corp
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Filing: 1994-12-20
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Granted: —
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Expires: 2014-12-20
Abstract
Abstract In an image encoding apparatus, image information is quantized and variable-length encoding is performed thereon so that the data are stored in a buffer. Thereafter, the data in the buffer are transmitted to the outside at a fixed data rate. At this time, a controller monitors a number of occupied bits in the buffer, and when the number of occupied bits is not more than thresholds, the controller switches the output of the apparatus to a dummy data generator. At this time, a parameter which is used for rate control is initialized, and dummy data which can be eliminated on a decoding circuit are outputted from the dummy data generator. Furthermore, bit allocation is changed so that a sum of the number of occupied bits and the bit allocation to a frame which is determined before encoding does not exceed a fixed amount. Moreover, when the number of occupied bits exceeds the fixed value, a quantization step size is changed to a greater value.
Inventors
- 👤 Hiroyuki Katata
- 👤 Hiroshi Kusao
- 👤 Yohichi Fujiwara
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 07:29
CPC Classifications
H; H04; H04N; H04N19/00; H04N19/10; H04N19/134; H04N19/146; H04N19/152; H04N19/102; H04N19/115; H04N19/124; H04N19/126; H04N19/136; H04N19/14; H04N19/149; H04N19/15; H04N19/157; H04N19/159; H04N19/169; H04N19/17; H04N19/172; H04N19/176; H04N19/60; H04N19/61; H04N19/50
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
262 words
An image encoding apparatus, comprising: quantizing means for quantizing information which corresponds to an image; variable-length encoding means for performing variable-length encoding on the quantized result of said quantizing means; temporary storage means for temporarily storing encoded data from said variable-length encoding means so as to transmit the stored encoded data to an outside at a fixed data rate; encoded data amount control means for calculating a quantization step size of quantizing information to be encoded based upon the encoded result of said variable-length encoding means so as to control an amount of the encoded data of said variable-length encoding means; dummy data generating means for generating dummy data which can be eliminated on a decoding circuit for decoding the encoded data; switching means for switching an output of said image encoding apparatus to either the encoded data from said temporary storage means or to the dummy data from said dummy data generating means; and control means for monitoring a number of occupied bits in said temporary storage means so as to control a switching operation of said switching means so that the output of the image encoding apparatus becomes the encoded data from said temporary storage means when the number of occupied bits exceeds a predetermined threshold, whereas so as to suspend transmission of data in said temporary storage means and control the switching operation of said switching means so that the output of the image encoding apparatus becomes the dummy data generated from said dummy data generating means when the number of occupied bits is not more than the threshold.
Claim 2
Dependent Claim
62 words
The image encoding apparatus as defined in claim 1, wherein: said control means outputs a switching signal into said encoded data amount control means when the number of occupied bits is not more than the thresholds; and said encoded data amount control means initializes various parameters which are used for calculation of the quantization step size when the switching signal is inputted.
Claim 3
Dependent Claim
216 words
The image encoding apparatus as defined in claim 2, wherein said encoded data amount control means includes: bit allocating means for calculating a degree of complexity in an image of a frame to be encoded from the encoded results up to the previous frame so as to determine a number of bits to be allocated to the frame to be encoded from the degree of complexity; reference quantization step size determining means for calculating a virtual buffer fullness based upon a number of generated bits obtained from said variable-length encoding means and a number of bits allocated by said bit allocating means so as to determine a reference quantization step size from the virtual buffer fullness; and quantization step size determining means for calculating activities showing fineness of a picture of an image so as to determine a quantization step size which is used in the quantizing means by changing the reference quantization step size based upon activities of an image to be encoded and an average value of the activities of the frame previously encoded, wherein the parameters which are initialized when the switching signal is inputted to said encoded data amount control means are the degree of complexity, the initial virtual buffer fullness and the average value of the activities on the previous frame.
Claim 4
Dependent Claim
59 words
The image encoding apparatus as defined in claim 1, further comprising: block dividing means for dividing one frame of the inputted image into a plurality of macroblocks; and two-dimensional orthogonal transforming means for carrying out two-dimensional orthogonal transformation on an output of said block dividing means, wherein said quantizing means quantizes an output of said two-dimensional orthogonal transforming means.
Claim 5
Dependent Claim
76 words
The image encoding apparatus as defined in claim 4, further comprising: motion compensation inter-frame predicting means for while calculating a motion vector of each macroblock by comparing a current frame with another frame, predicting a macroblock in the current frame from another frame, wherein intra-frame encoding is performed on a frame of I picture which appears at predetermined frame intervals and inter-frame prediction encoding is performed on a frame of pictures other than the I picture.
Claim 6
Dependent Claim
78 words
The image encoding apparatus as defined in claim 5, further comprising: subtracting means for obtaining a difference between image data which have been predicted by said motion compensation inter-frame predicting means and current input image data, wherein in the case where inter-frame prediction encoding is performed, two-dimensional orthogonal transformation is carried out on the prediction difference obtained in said subtracting means by said two-dimensional orthogonal transforming means and the transformed prediction difference is quantized by said quantizing means.
Claim 7
Dependent Claim
97 words
The image encoding apparatus as defined in claim 5, wherein said motion compensation inter-frame predicting means includes: inverse quantizing means for inversely quantizing the output of said quantizing means; inverse orthogonal transforming means for carrying out inverse orthogonal transformation on the output of said inverse quantizing means; a frame memory for storing image data which have been reconstructed by said inverse orthogonal transforming means; and motion compensation predicting circuit for calculating a motion vector from reconstructed image data in said frame memory and current input image data so as to predict a macroblock of a current frame.
Claim 8
Dependent Claim
50 words
The image encoding apparatus as defined in claim 1, wherein said dummy data generating means generates dummy data with an arbitrary data length which include a dummy data start code showing a start of the dummy data and a dummy data end code showing an end of the dummy data.
Claim 9
Dependent Claim
26 words
The image encoding apparatus as defined in claim 1, wherein said dummy data generating means successively generates predetermined dummy codes composed of a plurality of bits.
Claim 10
Dependent Claim
96 words
The image encoding apparatus as defined in claim 1, wherein: said variable-length encoding means adds a predetermined start code to a front of each frame, said dummy data generating means generates dummy data where same bits continue, said control means controls a switching operation of the switching means immediately after the start code is outputted from said temporary storage means so that the dummy data are outputted from said dummy data generating means successively after generating the start code in the case where the output of the image encoding apparatus is switched to the dummy data.
Claim 11
Dependent Claim
55 words
The image encoding apparatus as defined in claim 1, wherein: said temporary storage means stores a predetermined amount of dummy data which can be eliminated on a decoding circuit in an initial state, the thresholds are set to smaller values than the number of occupied bits in said temporary storage means in an initial state.
Claim 12
Dependent Claim
211 words
An image encoding apparatus, comprising: quantizing means for quantizing information which corresponds to an image; variable-length encoding means for performing variable-length encoding on the quantized result of said quantizing means; temporary storage means for temporarily storing encoded data from said variable-length encoding means so as to transmit the stored encoded data to an outside at a fixed data rate; and encoded data amount control means for calculating bit allocation per frame of information to be encoded based upon the encoded result of said variable-length encoding means, and calculating a quantization step size from the above calculated result, and adjusting the quantization step size of quantization in said quantizing means according to the above calculated result so as to control an amount of the encoded data of said variable-length encoding means, wherein said encoded data amount control means includes bit allocation changing means for monitoring a number of occupied bits in the temporary storage means so as to change the calculated bit allocation when the sum of bit allocation to a frame which has been calculated before encoding and a number of occupied bits in said temporary storage means at the time of the calculation of the bit allocation exceeds a predetermined threshold, such that the sum does not exceed the threshold.
Claim 13
Dependent Claim
197 words
The image encoding apparatus as defined in claim 12, wherein said encoded data amount control means includes: bit allocating means for calculating a degree of complexity in an image of a frame to be encoded from the encoded results up to the previous frame so as to determine a number of bits to be allocated to the frame to be encoded from the degree of complexity; said bit allocation changing means for changing the bit allocation obtained by said bit allocating means; reference quantization step size determining means for calculating a virtual buffer fullness based upon the number of generated bits obtained from said variable-length encoding means and the bit allocation changed by said bit allocation changing means so as to determine a reference quantization step size from the virtual buffer fullness; and quantization step size determining means for calculating activities showing fineness of a picture of an image so as to determine a quantization step size which is used in the quantization step size determining circuit by changing the reference quantization step size based upon activities of an image to be encoded and an average value of the activities of the frame to be previously encoded.
Claim 14
Dependent Claim
70 words
The image encoding apparatus as defined in claim 12, wherein said bit allocation changing means changes the bit allocation to a value obtained by subtracting the number of occupied bits from the threshold when the sum of the bit allocation to the frame calculated before encoding and the number of occupied bits in the temporary storage means at the time of calculation of the bit allocation exceeds the predetermined threshold.
Claim 15
Dependent Claim
59 words
The image encoding apparatus as defined in claim 12, further comprising: block dividing means for dividing one frame of the inputted image into a plurality of macroblocks; and two-dimensional orthogonal transforming means for carrying out two-dimensional orthogonal transformation on an output of said block dividing means, wherein said quantizing means quantizes an output of said two-dimensional orthogonal transforming means.
Claim 16
Dependent Claim
77 words
The image encoding apparatus as defined in claim 15, further comprising: motion compensation inter-frame predicting means for while calculating a motion vector of each macroblock by comparing a current frame with another frame, predicting a macroblock of the current frame from another frame, wherein intra-frame encoding is performed on a frame of an I picture which appears at predetermined frame intervals and inter-frame prediction encoding is performed on a frame of pictures other than the I picture.
Claim 17
Dependent Claim
78 words
The image encoding apparatus as defined in claim 16, further comprising: subtracting means for obtaining a difference between image data which have been predicted by said motion compensation inter-frame predicting means and current input image data, wherein in the case where inter-frame prediction encoding is performed, two-dimensional orthogonal transformation is carried out on the prediction difference obtained in said subtracting means by said two-dimensional orthogonal transforming means and the transformed prediction difference is quantized by said quantizing means.
Claim 18
Dependent Claim
98 words
The image encoding apparatus as defined in claim 16, wherein said motion compensation inter-frame predicting means includes: inverse quantizing means for inversely quantizing the output of said quantizing means; inverse orthogonal transforming means for carrying out inverse orthogonal transformation on the output of said inverse quantizing means; a frame memory for storing image data which have been reconstructed by said inverse orthogonal transforming means; and motion compensation predicting circuit for calculating a motion vector from the reconstructed image data in said frame memory and current input image data so as to predict a macroblock of a current frame.
Claim 19
Dependent Claim
58 words
The image encoding apparatus as defined in claim 12, wherein said encoded data amount control means further includes quantization step size changing means for monitoring a number of occupied bits in said temporary storage means so as to change the calculated quantization step size to a greater value when the number of occupied bits exceeds the predetermined threshold.
Claim 20
Dependent Claim
61 words
An image encoding apparatus in which image data is quantized and variable-length encoded and then stored into a temporary storage means for fixed data rate transmission, and in which dummy data which can be eliminated on decoding is output from the apparatus when it is detected that the occupied space in the temporary storage means is less than a predetermined threshold.
References Cited (Backward Citations)
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