JPS6376687A - Adaptation type difference encoding system - Google Patents
Adaptation type difference encoding systemInfo
- Publication number
- JPS6376687A JPS6376687A JP61221640A JP22164086A JPS6376687A JP S6376687 A JPS6376687 A JP S6376687A JP 61221640 A JP61221640 A JP 61221640A JP 22164086 A JP22164086 A JP 22164086A JP S6376687 A JPS6376687 A JP S6376687A
- Authority
- JP
- Japan
- Prior art keywords
- signal
- value
- quantization
- color
- brightness
- Prior art date
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- 230000006978 adaptation Effects 0.000 title 1
- 238000013139 quantization Methods 0.000 claims abstract description 70
- 238000000034 method Methods 0.000 claims description 25
- 230000003044 adaptive effect Effects 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims 1
- 230000000007 visual effect Effects 0.000 abstract description 9
- 239000003086 colorant Substances 0.000 abstract description 5
- 238000007906 compression Methods 0.000 abstract description 5
- 230000006835 compression Effects 0.000 abstract description 5
- 230000006866 deterioration Effects 0.000 abstract description 4
- 230000005540 biological transmission Effects 0.000 description 14
- 238000005070 sampling Methods 0.000 description 10
- 238000013144 data compression Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 3
- 241000282412 Homo Species 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000873 masking effect Effects 0.000 description 2
- 240000008543 Ficus hispida Species 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T9/00—Image coding
- G06T9/005—Statistical coding, e.g. Huffman, run length coding
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Compression Or Coding Systems Of Tv Signals (AREA)
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は、カラー画像信号を圧縮するための適応形差分
符号化方式に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an adaptive differential encoding method for compressing color image signals.
近年、TV会議システムやフルカラー静止画像伝送を実
用化するために、ディジタル画像情報の圧縮伝送方式の
開発が活発化しており、狭帯域伝送路に適した方法とし
て差分パルス・コード変調(DPCM)方式が注目され
ている。DPCM方式は基本的には、入力信号と予測信
号との差分を量子化し、符号化して伝送する方式である
。カラー画像の表色系にはYIQ、Y−R−Y−B−Y
、CIELAB、CIELUB等があるが、例えばRG
BやYIQのように、3つのパラメータを用い色彩を表
現する。DPCMによる従来の予測符号化方式では、こ
れら表色系の3つのパラメータ毎に相互に無関係に量子
化と符号化をしていた。In recent years, in order to put TV conference systems and full-color still image transmission into practical use, the development of compression transmission methods for digital image information has become active, and differential pulse code modulation (DPCM) is a method suitable for narrowband transmission lines. is attracting attention. The DPCM method is basically a method in which the difference between an input signal and a predicted signal is quantized, encoded, and transmitted. The color system for color images is YIQ, Y-R-Y-B-Y.
, CIELAB, CIELUB, etc. For example, RG
Colors are expressed using three parameters, such as B and YIQ. In the conventional predictive coding method using DPCM, quantization and coding were performed for each of these three parameters of the color system independently of each other.
人間の視覚特性についての検討の結果、画像データを量
子化する場合、人間の視覚に認識されえない量子化誤差
は、色彩の各パラメータの大きさに依存することが知ら
れている。量子化とは、ある値範囲内にある値をその範
囲内の特定の値で代表させ、連続量を離散化することで
あり、真値とその代表値との差が量子化誤差である。量
子化誤差が人間の視覚特性に与える影響は、表色系のパ
ラメータに対し振幅の制限された一様雑音を予め加算し
、その振幅に対する検知限を調べればよく、それにより
、色調によってどの程度の量子化誤差が許容可能かを知
ることが出来る。As a result of studies on human visual characteristics, it is known that when image data is quantized, quantization errors that cannot be recognized by human vision depend on the magnitude of each color parameter. Quantization refers to making a value within a certain value range representative by a specific value within that range, thereby discretizing a continuous quantity, and the difference between the true value and its representative value is the quantization error. The effect of quantization error on human visual characteristics can be determined by adding uniform noise with limited amplitude to the parameters of the color system in advance and examining the detection limit for that amplitude. It is possible to know whether the quantization error of is tolerable.
人間の視覚には、画像の変化の激しい部分では振幅誤差
が画像データに生じていても検知され難いというマスキ
ング現象がある。即ち、信号が急激に変化している部分
と、あまり変化せず平坦な部分とでは、誤差の許容レベ
ルが異なり、急激に信号強さ、特に明るさが変化する部
分ではかなり大きな誤差が許容される。この視覚特性か
ら、前値予測の符号化方式(後値予測でも同様)におい
て前値との差分を量子化する場合に、差分値の大きな部
分では量子化誤差が大きくても人間にはその誤差が認識
されず、従って、差分値の大きな部分では量子化範囲幅
を広くする非線形量子化を採用出来る。非線形量子化を
採用するとデータ圧縮効率を高めることができ、従来の
差分符号化方式では非線形量子化を採用するものが多い
。Human vision has a masking phenomenon in which it is difficult to detect amplitude errors even if they occur in image data in areas where the image changes rapidly. In other words, the allowable level of error is different between parts where the signal changes rapidly and parts where the signal does not change much and is flat, and a fairly large error is allowed in parts where the signal strength, especially the brightness, changes rapidly. Ru. Due to this visual characteristic, when quantizing the difference from the previous value in the encoding method of previous value prediction (same for subsequent value prediction), even if the quantization error is large in the part where the difference value is large, humans cannot see the error. is not recognized, therefore, nonlinear quantization that widens the quantization range width can be adopted in parts where the difference value is large. Employing nonlinear quantization can improve data compression efficiency, and many conventional differential encoding systems employ nonlinear quantization.
この非線形量子化特性は例えば、原点を通り許容量子化
誤差曲線(又は直線)と差分値軸との間で交互し且つ差
分値軸に45度で交差する折れ線を引き、その折れ線と
許容量子化曲線との交点によって決定される。This nonlinear quantization characteristic can be expressed, for example, by drawing polygonal lines passing through the origin and alternating between the allowable quantization error curve (or straight line) and the difference value axis, and intersecting the difference value axis at 45 degrees, and connecting the polygonal lines with the allowable quantization Determined by the intersection with the curve.
ところがこれらの表色系は、人間の視覚特性から考えて
必ずしも均一な空間ではない。即ち、同一のノルムを持
つ色彩の変化に対し人間が知覚する色差は、表色系に占
める位置によって大きく異なる。従って従来の予測符号
化方式方式では、人間の視覚特性に適合したデータ圧縮
を行っておらず、圧縮効率のよいものでは無かった。However, these color systems are not necessarily uniform spaces considering human visual characteristics. That is, the color difference that humans perceive when a color has the same norm varies greatly depending on its position in the color system. Therefore, the conventional predictive encoding method does not perform data compression that is compatible with human visual characteristics, and therefore does not have good compression efficiency.
そこで本発明は、カラー画像を表現している表色系の各
成分に対する人間の視覚特性の許容量子化誤差を考慮し
、画質劣化を伴わずカラー画像信号の圧縮効率をより高
くすることができる適応形差分符号化方式を提示するこ
とを目的とする。Therefore, the present invention takes into account the permissible quantization error of human visual characteristics for each component of the color system expressing a color image, and can further improve the compression efficiency of color image signals without deteriorating image quality. The purpose of this paper is to present an adaptive differential encoding method.
C問題点を解決するための手段〕
本発明に係る適応形差分符号化方式は、カラー画像信号
を標本化して標本化信号を得て、前記標本化信号から差
分信号を形成し、前記差分信号を゛量子化して符号化す
る方式であって、カラー画像を表現する各成分毎の差分
信号の量子化特性を調定する際に色彩の明るさを表す成
分については色彩の明るさを表す成分の予測値に従い設
定された許容量子化誤差に応じて適応的に差分信号の量
子化特性を調定し、色を表す成分については色彩の明る
さを表す成分の予測値と現在の色彩の明るさを表す成分
値に従い設定された許容量子化誤差に応じて差分信号の
量子化特性を調定する方式である。Means for Solving Problem C] The adaptive differential encoding method according to the present invention samples a color image signal to obtain a sampled signal, forms a difference signal from the sampled signal, and generates a difference signal from the sampled signal. In this method, when adjusting the quantization characteristics of the difference signal for each component expressing a color image, the component representing the brightness of the color is quantized and encoded. The quantization characteristics of the difference signal are adaptively adjusted according to the allowable quantization error set according to the predicted value of This method adjusts the quantization characteristics of the difference signal according to the allowable quantization error set according to the component value representing the difference.
上述の方式によりカラー画像信号を表現する各成分毎に
許容量子化誤差を設定し、量子化特性を前記許容量子化
誤差に応じて調定することにより、量子化誤差による画
質劣化を押さえ、また量子化効率を高めることができる
。By setting an allowable quantization error for each component expressing a color image signal using the above-mentioned method and adjusting the quantization characteristics according to the allowable quantization error, image quality deterioration due to quantization errors can be suppressed, and Quantization efficiency can be increased.
−4 =
本発明では、色彩の明るさを表す成分については、前画
素の明るさ成分値を参照して許容量子化誤差を決定して
量子化特性を選定し、色信号成分については、現在注目
している画素の明るさ成分値をも併せて参照して許容量
子化誤差を決定して量子化特性を選定する。色信号成分
のこのような取り扱いにより、人間の視覚特性を考慮に
入れたデータ圧縮率の良い符号化を行え、画像の劣化も
生じない。−4 = In the present invention, for the component representing the brightness of the color, the allowable quantization error is determined by referring to the brightness component value of the previous pixel and the quantization characteristic is selected, and for the color signal component, the quantization characteristic is selected by referring to the brightness component value of the previous pixel. The brightness component value of the pixel of interest is also referred to to determine the permissible quantization error and select the quantization characteristic. By handling the color signal components in this manner, it is possible to perform encoding with a high data compression rate that takes human visual characteristics into account, and no image deterioration occurs.
以下、図面を参照して、本発明の方式を実施する回路構
成例を図示した図面を参照・説明することにより、本発
明の詳細な説明する。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings, which illustrate an example of a circuit configuration for implementing the method of the present invention.
第1図は、Y、R−Y、B−Y表色系において本発明に
係る方式を実施する回路の送受信系を示す。本発明では
色信号成分の量子化に注目画素の明るさ信号、即ち輝度
(Y)信号を参照する必要があるため、図示例で、Y信
号が標本時点i+1のものであるのに対し、R−Y、B
−Y信号は時点iのものであることに注意されたい。主
に輝度信号Yの系列で説明するが、R−Y信号系列及び
B−Y信号系列においてY信号系列の回路要素に対応す
る要素には、数値符号の後にYの代わりにそれぞれR及
びBを付した。真価と量子化され量子化誤差を含む値と
を区別するため、量子化値の記号にプライム(“)を付
した。FIG. 1 shows a transmitting/receiving system of a circuit implementing the method according to the present invention in the Y, R-Y, B-Y color system. In the present invention, it is necessary to refer to the brightness signal of the pixel of interest, that is, the luminance (Y) signal, for quantization of the color signal component. -Y,B
Note that the -Y signal is at time i. The explanation will mainly be based on the luminance signal Y series, but in the R-Y signal series and B-Y signal series, elements corresponding to circuit elements of the Y signal series have R and B after the numerical code, respectively, instead of Y. Attached. In order to distinguish between the true value and the value that has been quantized and includes a quantization error, a prime (“) is attached to the symbol of the quantized value.
送信系Aにおいて加減算器10Yは、標本化されたy、
+1と予測器12Yからの前画素の量子化された値(予
測値)y1’ との差分を計算する。In the transmission system A, the adder/subtractor 10Y receives the sampled y,
+1 and the quantized value (predicted value) y1' of the previous pixel from the predictor 12Y is calculated.
量子化器14Yは、加減算器10Yからの差分値yi。The quantizer 14Y receives the difference value yi from the adder/subtractor 10Y.
+ 3’i”を量子化する。量子化器14Yは予測
器12Yからの予測値Y!’を受け、対応する許容量子
化誤差に基づく非線形量子化特性で入力信号を量子化す
る。符号化器16Yは、量子化器14Yからの量子化信
号(代表値)yi。1゛を二進符号化する。符号化器1
6Yは例えば、出現頻度の高い代表値には短い符号を割
り当て、出現頻度の低い代表値には長い符号を割り当て
る。+3'i''. The quantizer 14Y receives the predicted value Y!' from the predictor 12Y and quantizes the input signal with a nonlinear quantization characteristic based on the corresponding allowable quantization error. Encoding The encoder 16Y binary encodes the quantized signal (representative value) yi.1'' from the quantizer 14Y.Encoder 1
For example, in 6Y, a short code is assigned to a representative value that appears frequently, and a long code is assigned to a representative value that appears less frequently.
量子化特性切換回路18は、予測器12Yの出力y 、
l と、1画素分の遅延回路19による代表値yi−
+’ とを受け、R−Y信号の量子化器14R及びB−
Y信号の量子化器14Bに指示して各量子化特性を最適
なものに選択設定させる。即ち、Vi’が大きい程、及
びyi−+ ’ とy、゛の差が大きい程、量子化誤差
が認識されない程度で粗な分割になる非線形量子化特性
を選択させる。これにより差分代表値の数が減り、短い
符号の割り当て率が増す。The quantization characteristic switching circuit 18 outputs the output y of the predictor 12Y,
l and the representative value yi- by the delay circuit 19 for one pixel
+', the R-Y signal quantizers 14R and B-
The Y signal quantizer 14B is instructed to select and set each quantization characteristic to the optimum one. That is, the larger Vi' and the larger the difference between yi-+' and y,', the more a non-linear quantization characteristic is selected that provides coarse division to such an extent that no quantization error is recognized. This reduces the number of differential representative values and increases the allocation rate of short codes.
量子化器14Rは、R−Y信号の時点iの量子化信号を
符号化器16Rと、連係の予測器12Rとに印加する。The quantizer 14R applies the quantized signal at time i of the RY signal to the encoder 16R and the conjunction predictor 12R.
また量子化器14Bは、B−Y信号の時点iの量子化信
号を符号化器16Bと、連係の予測器12Bとに印加す
る。The quantizer 14B also applies the quantized signal at time i of the BY signal to the encoder 16B and the conjunction predictor 12B.
予測器12Y、12R,12Bは、一般的に、差分量子
化代表値に前値を加算する加算器と、当該加算器の出力
を1画素分遅延させる遅延回路とからなり、当該遅延回
路の出力が予測器の出力となり、また当該遅延回路の出
力は当該加算器にも印加され、入力差分信号の復元に利
用される。The predictors 12Y, 12R, and 12B generally include an adder that adds a previous value to the differential quantization representative value, and a delay circuit that delays the output of the adder by one pixel. becomes the output of the predictor, and the output of the delay circuit is also applied to the adder and used to restore the input difference signal.
符号化器16Y、16R,16BのDPCM出力は、伝
送路20Y、20R,20Bを介して、受信系Bに送ら
れる。受信系Bでは、復号器30Y、30R,30Bが
伝送路20Y、20R,2OBのDPCM信号を復号し
、加算器32Y、32R,32Bに送る。加算器32Y
、32R,32Bは、送信系Aでの予測器12Y、12
R,12Bと同様の予測器34Y、34R,34Bから
の予測値yi”+ r yl−1’ l bFト1
’をそれぞれ復号器30Y、30R,30Bの出力に加
算し、色彩の各成分信号y!。、”+ 、、+ +
by=°を出力する。加算器32Y、32R,32B
の出力はそれぞれ連係する予測器34Y、34R,34
Bにも印加され、加算器32Y、32R,32Bでの信
号復元に利用される。The DPCM outputs of encoders 16Y, 16R, and 16B are sent to receiving system B via transmission lines 20Y, 20R, and 20B. In receiving system B, decoders 30Y, 30R, and 30B decode the DPCM signals on transmission lines 20Y, 20R, and 2OB, and send them to adders 32Y, 32R, and 32B. Adder 32Y
, 32R, 32B are predictors 12Y, 12 in the transmission system A.
Predicted values from predictors 34Y, 34R, 34B similar to R, 12B
' are added to the outputs of the decoders 30Y, 30R, and 30B, respectively, and each color component signal y! . ,”+ ,,+ +
Output by=°. Adders 32Y, 32R, 32B
The outputs of the respective predictors 34Y, 34R, 34
It is also applied to B and used for signal restoration in adders 32Y, 32R, and 32B.
受信系Bの復号器30Yは、予測器34Yの出力V+’
により送信系Aの量子化及び符号化特性に対応する復
号特性に選択・設定される。復号化特性切換回路40は
、予測器34Yからの予測値yi”と1画素分の遅延回
路42によるyi−+’とを受け、R−Y信号の復号器
30R及びB−Y信号の復号器30Bの復号特性を送信
系Aでの量子化及び符号化特性に対応するものに設定さ
せる。The decoder 30Y of the receiving system B receives the output V+' of the predictor 34Y.
The decoding characteristics are selected and set to correspond to the quantization and encoding characteristics of the transmission system A. The decoding characteristic switching circuit 40 receives the predicted value yi'' from the predictor 34Y and the yi-+' from the one-pixel delay circuit 42, and switches the decoder 30R for the R-Y signal and the decoder for the B-Y signal. The decoding characteristics of 30B are set to correspond to the quantization and encoding characteristics of the transmission system A.
受信側での前値予測値は送信側での前値予測値と同じ値
であるため、このアルゴリズムにより受信系Bにおいて
完全な復元を実現出来る。Y信号、R−Y信号及びB−
Y信号で符号化及び復号のアルゴリズムは同じであるが
、成分毎に許容量子化誤差が異なるので、量子化器14
Y、14R,14B及び復号器30Y、30R,30B
の伝達特性は、当然ながら個々に異なる。Since the predicted previous value on the receiving side is the same as the predicted previous value on the transmitting side, complete restoration can be achieved in the receiving system B using this algorithm. Y signal, RY signal and B-
Although the encoding and decoding algorithms are the same for the Y signal, the allowable quantization error differs for each component, so the quantizer 14
Y, 14R, 14B and decoders 30Y, 30R, 30B
Naturally, the transmission characteristics of each individual device are different.
標本点i−1におけるY信号値3’t−tが比較的小さ
く、標本点iにおけるY(が比較的大きい場合に標本点
iの信号yi+ rITi+ b、iの差分及び量
子化を考えると、前画素の輝度信号値yi−+’により
各成分(パラメータ)の許容量子化誤差を決定する方式
では、Y、R−Y、B−Y信号の全てに対して、マスキ
ング現象を利用した第5A図に示すような密な非線形量
子化特性が選択される。When the Y signal value 3't-t at sampling point i-1 is relatively small and Y( at sampling point i is relatively large, considering the difference and quantization of the signal yi+ rITi+ b, i at sampling point i, In the method of determining the permissible quantization error of each component (parameter) based on the luminance signal value yi-+' of the previous pixel, the 5A method using the masking phenomenon is A dense nonlinear quantization characteristic as shown in the figure is selected.
ところが、注目画素で輝度の変化両が前画素に対して大
きい場合、色を表す信号には本来より大きな量子化誤差
が許容されるのであり、R−Y、 B−Y信号のデー
タ圧縮効率が低くなる。本発明は、注目画素の輝度信号
値をも参照することによって、第6A図に示すようなよ
り粗な量子化特性を選択するようにして、データ圧縮効
率を高める。なお、第5B図及び第6B図はそれぞれ第
5A図及び第6A図の零点付近の拡大図である。However, if the change in luminance of the pixel of interest is larger than that of the previous pixel, a larger quantization error is allowed in the signal representing the color than originally intended, and the data compression efficiency of the R-Y and B-Y signals decreases. It gets lower. The present invention improves data compression efficiency by selecting coarser quantization characteristics as shown in FIG. 6A by also referring to the luminance signal value of the pixel of interest. Note that FIGS. 5B and 6B are enlarged views of the vicinity of the zero point in FIGS. 5A and 6A, respectively.
NTSC信号のようにR−Y、B−Y信号が帯域制限さ
れている場合には、Y信号の標本周期に対してその1/
2.1/4等の標本化周波数でR−Y、B−Y信号をサ
ンプリングする場合が考えられる。第2図に1/2の標
本化周波数による標本位置を示す。このような場合、前
画素の輝度信号を参照して量子化特性を決定する構成で
は、標本点iの標本値rVi+ t)y(に対し、標
本点i−2のy14′を使って標本点i−2の標本値r
yi−1+b 7L−2との差分量子化特性を設定する
ことになる。If the R-Y and B-Y signals are band-limited like the NTSC signal, the sample period of the Y signal is 1/
A case can be considered in which the RY and BY signals are sampled at a sampling frequency such as 2.1/4. FIG. 2 shows sampling positions at 1/2 sampling frequency. In such a case, in a configuration in which the quantization characteristic is determined by referring to the luminance signal of the previous pixel, the sample value rVi + t)y (for the sample point i) is determined using the sample value y14' of the sample point i-2. sample value r of i-2
The differential quantization characteristic with yi-1+b 7L-2 will be set.
ところが、この場合には2画素分離れてしまうので、Y
信号の相関が低く、)’i−z”を使っての量子化特性
の決定は不適切である。However, in this case, they are separated by two pixels, so Y
Since the signal correlation is low, it is inappropriate to determine the quantization characteristics using )'i-z'.
これに本発明を適用する場合、標本時点i−’lと同i
におけるY信号の値を利用すればよい。この構成例を第
3図に示す。第3図の例で、ry。When applying the present invention to this, the same i as the sample time i-'l
What is necessary is to use the value of the Y signal in . An example of this configuration is shown in FIG. In the example of FIG. 3, ry.
byの処理に対しyの処理を2画素分先行させているの
は、標本時点iにおけるr、、b、の処理のために標本
時点t、i−2のy”の値が必要だからである。第3図
において第1図の回路要素と同じものには同じ符号を付
した。The reason why the processing of y precedes the processing of by by two pixels is because the value of y" at sample time t, i-2 is required for processing r,,b, at sample time i. 3, circuit elements that are the same as those in FIG. 1 are given the same reference numerals.
第3図の構成では、Y信号の送信系Aの予測器42Yは
、送信系AのY信号人力y、。2に対し2画素前の予測
値yi’を出力し、対応する受信系Bでの予測器44Y
も2画素前のyloを出力する。第1図の量子化特性切
換回路18に対応する送信系Aの量子化切換回路46は
、送信系Aの予測器42Yの出力y、”と、遅延回路4
8及び同50により2画素分先行する量子化値y4−z
” とを受け、切換信号を量子化器14R,14Bに供
給する。第1図の量子化特性切換回路40に対応する受
信系Bの復号化切換回路52は、受信系Bの予測器44
Yの出力yi’ と遅延回路54及び同56により2画
素分先行する量子化値Y +−z′−12=
とを受け、切換信号を復号器30R,30Bに供給する
。In the configuration of FIG. 3, the predictor 42Y of the Y signal transmission system A calculates the Y signal of the transmission system A manually by y. 2, the predicted value yi' of two pixels before is output, and the predictor 44Y in the corresponding receiving system B
also outputs ylo two pixels before. The quantization switching circuit 46 of the transmission system A corresponding to the quantization characteristic switching circuit 18 of FIG.
8 and 50, the quantized value y4-z precedes by 2 pixels
” and supplies switching signals to the quantizers 14R and 14B.The decoding switching circuit 52 of the receiving system B, which corresponds to the quantization characteristic switching circuit 40 in FIG.
The output yi' of Y and the quantized value Y+-z'-12= which precedes by two pixels are received by the delay circuits 54 and 56, and a switching signal is supplied to the decoders 30R and 30B.
Y信号について第1図のように直前画素の量子化値を予
測値にしたい場合には、その予測器42Yの出力yユ。When it is desired to use the quantized value of the immediately preceding pixel as a predicted value for the Y signal as shown in FIG. 1, the output y of the predictor 42Y is used.
1゛を遅延回路で1画素分遅延させればよい。It is only necessary to delay 1゛ by one pixel using a delay circuit.
第3図の回路では、R−Y、B−Y信号についてrIl
j+ byj (1とjの関係は第2図参照)が入力
信号となり、標本時点j−1の前値との差分符号化が行
われる。受信系Bで、も同様である。In the circuit of FIG. 3, rIl for the R-Y and B-Y signals.
j+byj (see FIG. 2 for the relationship between 1 and j) becomes an input signal, and differential encoding with the previous value at sampling time j-1 is performed. The same goes for receiving system B.
量子化特性のよりきめ細かい設定を行うために、第4図
に示すように、遅延回路48の出力から切換回路46
(及び52)に量子化値yi−+’ をも入力してもよ
い。Y i−zo とyi゛が同じ程度の大きさである
場合、3’ i−1′ に関わらず、第3図の構成では
yi−2”及び差分値に従い細かい分割の量子化特性が
設定される。ところが、7+−+’が例えば極めて小さ
くyi” との差が大きいときには、粗な量子化特性を
採用できるのであり、従って、第4図のようにyi−+
”の値も参照するのが好ましい。このようにR−Y、B
−Y信号の標本化周波数をY信号の標本化周波数より小
さくしても、本発明の方式は有効に利用出来る。In order to make more detailed settings for the quantization characteristics, as shown in FIG.
The quantized value yi-+' may also be input to (and 52). When Y i-zo and yi゛ are of the same size, the quantization characteristic of fine division is set according to yi-2'' and the difference value in the configuration of Fig. 3, regardless of 3'i-1'. However, when 7+-+' is, for example, extremely small and has a large difference from yi'', a coarse quantization characteristic can be adopted, and therefore, as shown in Figure 4, yi-+
It is preferable to also refer to the value of ``.In this way, R-Y, B
- Even if the sampling frequency of the Y signal is lower than the sampling frequency of the Y signal, the method of the present invention can be effectively used.
図示例ではY信号、R−Y信号及びB−Y信号を別々の
伝送路で伝送するように説明したが、現実の構成では、
Y、R−Y、B−Yのそれぞれの符号化が行われた後で
これらをシリアル信号に変換して伝送路に送出し、受信
系Bでこれを3つに分解して復号する。但し、本発明で
は復号のために輝度情報が必要であるので、R−Y信号
及びB−Y信号についてはY信号に較べ1画素分遅延さ
せる構成をとってもよい。また、ry、byの処理のた
めに1又は2画素分Y信号を先行させているが、Y信号
の処理がR−Y信号及びB−Y信号より1又は2画素分
以上先行していればよいのであるから、例えば、Y信号
の1画面分の処理を先に行って量子化データをバッファ
・メモリに一時保存し、その内容を参照してR−Y信号
及びB−Y信号の処理を行ってもよい。In the illustrated example, the Y signal, R-Y signal, and B-Y signal are transmitted through separate transmission paths, but in the actual configuration,
After each of Y, R-Y, and B-Y is encoded, they are converted into serial signals and sent to the transmission path, and the reception system B decomposes them into three parts and decodes them. However, since the present invention requires luminance information for decoding, the RY signal and the BY signal may be delayed by one pixel compared to the Y signal. Also, the Y signal is preceded by 1 or 2 pixels for ry and by processing, but if the Y signal processing precedes the RY signal and the BY signal by 1 or 2 pixels or more, then For example, it is possible to process one screen of the Y signal first, temporarily store the quantized data in a buffer memory, and then process the R-Y signal and B-Y signal by referring to the contents. You may go.
以上の説明では、Y−R−Y−B−Y表色系での例を示
したが、本発明の方法は、他の表色系、例えばYIQ、
、La*b*、Lu* v*表色系では、それぞれY、
L、Lが明るさを表現しているので、そのY、L、Lの
予測値を用いて最適の量子化特性を設定出来る。また、
RGB系ではG信号が明るさを近似的に表しているので
、G信号のを図示例のY信号に対応させ、R信号及びB
信号を図示例のR−Y信号及びB−Y信号に対応させれ
ばよい。In the above explanation, an example was given using the Y-R-Y-B-Y color system, but the method of the present invention can also be applied to other color systems, such as YIQ,
, La*b*, Lu*v* color system, Y, respectively.
Since L and L express brightness, the optimal quantization characteristics can be set using the predicted values of Y, L, and L. Also,
In the RGB system, the G signal approximately represents brightness, so the G signal is made to correspond to the Y signal in the illustrated example, and the R signal and B
The signals may be made to correspond to the RY signal and BY signal in the illustrated example.
以上、説明したように、本発明によれば、簡単な回路構
成でカラー画像信号を表現している表色系の各成分に対
する人間の視覚特性の許容量子化誤差に応じて適応的に
差分符号化を行うので、画質劣化が少なくしかもカラー
画像信号の圧縮効率を高くすることができる適応形差分
符号化方式を提示することが出来る。As described above, according to the present invention, a differential code is adaptively applied according to the permissible quantization error of human visual characteristics for each component of a color system expressing a color image signal using a simple circuit configuration. Therefore, it is possible to present an adaptive differential encoding method that can reduce image quality deterioration and increase the compression efficiency of color image signals.
第1図は、本発明に係る適応形予測符号化方式を実施す
るための送受信回路構成の一例、第2図はNTSC信号
でY信号の標本化周期の2倍の周期でR−Y、B−Y信
号を標本化する場合の標本位置関係を説明する図、第3
図は、第2図に示す標本信号を本発明により差分符号化
及び復号する回路構成例、第4図は第3図の回路の一部
を変形した回路構成例を示す図、第5A図、第5B図、
第6A図及び第6B図は、本発明において用いられる非
線形量子化特性を例示する図である。
10Y、IOR,l0B−・−加減算器 12Y、12
R,12B、42Y−・予測器 14Y、14R。
14 B−量子化器 16Y、 16R,16B−符
号化器 18.46・−切換回路 19,48,5〇−
遅延回路 20Y、2OR,20B−伝送路30Y、3
0R,30B−復号器 32Y、32R,32B・−加
算器 34Y、34R,34B。
44Y−予測器 40.52−切換回路 42゜54.
56・−・遅延回路
第5A図
4殖
特開口UG3−76[i87 (7)川
第5B図
嚇FIG. 1 shows an example of a transmitting/receiving circuit configuration for implementing the adaptive predictive coding method according to the present invention, and FIG. 2 shows an NTSC signal with R-Y, - Diagram explaining the sample position relationship when sampling the Y signal, Part 3
The figure shows an example of a circuit configuration for differentially encoding and decoding the sample signal shown in FIG. 2 according to the present invention, FIG. Figure 5B,
FIGS. 6A and 6B are diagrams illustrating nonlinear quantization characteristics used in the present invention. 10Y, IOR, l0B--Adder/subtractor 12Y, 12
R, 12B, 42Y--Predictor 14Y, 14R. 14 B-quantizer 16Y, 16R, 16B-encoder 18.46・-switching circuit 19,48,50-
Delay circuit 20Y, 2OR, 20B-transmission line 30Y, 3
0R, 30B - Decoder 32Y, 32R, 32B - Adder 34Y, 34R, 34B. 44Y-Predictor 40.52-Switching circuit 42°54.
56...Delay circuit Fig. 5A 4 special opening UG3-76 [i87 (7) River Fig. 5B
Claims (1)
本化信号から差分信号を形成し、前記差分信号を量子化
して符号化する方式であって、カラー画像を表現する各
成分毎の差分信号の量子化特性を調定する際に色彩の明
るさを表す成分については色彩の明るさを表す成分の予
測値に従い設定された許容量子化誤差に応じて適応的に
差分信号の量子化特性を調定し、色を表す成分について
は色彩の明るさを表す成分の予測値と現在の色彩の明る
さを表す成分値に従い設定された許容量子化誤差に応じ
て適応的に差分信号の量子化特性を調定することを特徴
とする適応形差分符号化方式。A method in which a color image signal is sampled to obtain a sampled signal, a difference signal is formed from the sampled signal, and the difference signal is quantized and encoded. When adjusting the quantization characteristics of the signal, the quantization characteristics of the difference signal are adaptively adjusted according to the allowable quantization error set according to the predicted value of the component representing the brightness of the color. and for the component representing color, the quantum of the difference signal is adaptively adjusted according to the allowable quantization error set according to the predicted value of the component representing the brightness of the color and the component value representing the current brightness of the color. An adaptive differential encoding method characterized by adjusting the conversion characteristics.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP61221640A JPS6376687A (en) | 1986-09-19 | 1986-09-19 | Adaptation type difference encoding system |
US07/413,954 US5072290A (en) | 1986-09-19 | 1989-09-28 | Color image signal encoding device |
US08/132,687 US5428394A (en) | 1986-09-19 | 1993-10-07 | Adaptive type differential encoding method and device |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP61221640A JPS6376687A (en) | 1986-09-19 | 1986-09-19 | Adaptation type difference encoding system |
Publications (1)
Publication Number | Publication Date |
---|---|
JPS6376687A true JPS6376687A (en) | 1988-04-06 |
Family
ID=16769944
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP61221640A Pending JPS6376687A (en) | 1986-09-19 | 1986-09-19 | Adaptation type difference encoding system |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS6376687A (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0267887A (en) * | 1988-09-02 | 1990-03-07 | Ricoh Co Ltd | Picture data input system and picture data input device in picture transfer display for telephone |
EP0490539A2 (en) * | 1990-12-11 | 1992-06-17 | AT&T Corp. | Adaptive non-linear quantizer |
EP0535963A2 (en) * | 1991-10-02 | 1993-04-07 | Matsushita Electric Industrial Co., Ltd. | Orthogonal transformation encoder |
US5475433A (en) * | 1993-04-15 | 1995-12-12 | Samsung Electronics Co., Ltd. | Fuzzy-controlled coding method and apparatus therefor |
US5526052A (en) * | 1993-02-25 | 1996-06-11 | Hyundai Electronics Ind. Co., Ltd. | Quantization adaptive to the human visual system |
WO2005107147A1 (en) * | 2004-04-28 | 2005-11-10 | Hitachi, Ltd. | Authentication system, authentication acquisition device, and authentication method |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS6033789A (en) * | 1983-08-03 | 1985-02-21 | Matsushita Electric Ind Co Ltd | Method for transmitting picture to be coded |
-
1986
- 1986-09-19 JP JP61221640A patent/JPS6376687A/en active Pending
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS6033789A (en) * | 1983-08-03 | 1985-02-21 | Matsushita Electric Ind Co Ltd | Method for transmitting picture to be coded |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0267887A (en) * | 1988-09-02 | 1990-03-07 | Ricoh Co Ltd | Picture data input system and picture data input device in picture transfer display for telephone |
EP0490539A2 (en) * | 1990-12-11 | 1992-06-17 | AT&T Corp. | Adaptive non-linear quantizer |
EP0535963A2 (en) * | 1991-10-02 | 1993-04-07 | Matsushita Electric Industrial Co., Ltd. | Orthogonal transformation encoder |
US5369439A (en) * | 1991-10-02 | 1994-11-29 | Matsushita Electric Industrial Co., Ltd. | Orthogonal transform encoder using DC component to control quantization step size |
US5526052A (en) * | 1993-02-25 | 1996-06-11 | Hyundai Electronics Ind. Co., Ltd. | Quantization adaptive to the human visual system |
US5475433A (en) * | 1993-04-15 | 1995-12-12 | Samsung Electronics Co., Ltd. | Fuzzy-controlled coding method and apparatus therefor |
WO2005107147A1 (en) * | 2004-04-28 | 2005-11-10 | Hitachi, Ltd. | Authentication system, authentication acquisition device, and authentication method |
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