JPS634782A - High efficient coding device - Google Patents

Abstract

PURPOSE:To increase the compressing ratio by executing a coding with a quantizing step suitable to an action quantity. CONSTITUTION:The device has a dynamic range detecting circuit 4 to obtain the maximum value of plural picture element data and the minimum value of plural picture element data included in a block composed of the area belonging to plural respective continuous fields of a digital image signal and detect a dynamic range at every block from the maximum value and the minimum value, an action quantity detecting circuit 3 to decide the action quantity of the image at every block and generate an action code SJ, a subtracting circuit 5 to subtract the minimum value from the value of plural picture element data and form input data after the minimum value is removed, and a quantizing circuit 8 which codes the input data after the minimum value is removed in the detected dynamic range with the number of the quantizing bit less than the original number of the quantizing bit and in which the quantizing step of the coding is suitably determined corresponding to the action quantity given by the action code. Dynamic information, at least two additional codes in the minimum value and the maximum value, a code signal obtained by coding and a discriminating code are transmitted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-efficiency encoding device that compresses the number of bits per pixel of image data such as a digital television signal.

[Summary of the invention]

In a high-efficiency encoding device applied to transmit digital television signals, the present invention divides a television screen into a large number of three-dimensional blocks, that is, spatial blocks, and calculates the correlation between pixels within each block. By encoding that adapts to the narrower dynamic range, pixel data within a block can be encoded with a compressed number of bits, making it possible to form transmission data with a reduced number of bits compared to the number of bits of the original data. At the same time, the amount of motion in the image is detected for each block, a motion code indicating the amount of motion is generated, and redundancy in the temporal direction can be removed by encoding with a quantization step adapted to the amount of motion. It is.

[Conventional technology]

As methods for encoding television signals, several methods are known in which the average number of bits per pixel or the sampling frequency is reduced in order to narrow the transmission band.

As an encoding method to lower the sampling frequency, image data is thinned out to 172 by subsampling, and the subsampling point and the position of the subsampling point used during interpolation are indicated (i.e., which subsampling point is above, below or to the left or right of the interpolation point? A method has been proposed that transmits a flag (indicating whether point data is used).

One of the encoding methods that reduces the average number of bits per pixel is D PCM (differenti
alPCM) is known. DPCM takes into consideration the fact that the pixels of a television signal have a high correlation and the difference between adjacent pixels is small, and this difference signal is quantized and transmitted.

Another encoding method that reduces the average number of bits per pixel is to subdivide one field screen into small blocks and calculate the deviation of the pixel at the representative point and the level distribution of data within each block for each block. There is something that transmits

[Problem that the invention seeks to solve]

The encoding method that attempts to reduce the sampling frequency using subsampling has a sampling frequency of 172
Therefore, there was a risk that aliasing distortion would occur.

D PCM has a problem in that errors propagate to subsequent decoding.

The "method of encoding in units of blocks" has the drawback that block distortion occurs at the boundaries between blocks.The object of the present invention is to eliminate the generation of aliasing distortion, error propagation, and block distortion that the above-mentioned conventional techniques have. It is an object of the present invention to provide a highly efficient encoding device that does not cause problems such as generation.

The principal applicant of the present invention determined the dynamic range defined by the maximum and minimum values of a plurality of pixels included in a two-dimensional block, as described in Japanese Patent Application No. 59-266407, and We have proposed a high-efficiency encoding device that performs range-adaptive encoding. Also,
An encoding method adapted to the dynamic range has been proposed for a three-dimensional block formed from pixels included in a plurality of fields, as described in Japanese Patent Application No. 60-232789.

In these encoding methods adapted to the dynamic range, the quantization step is the same for blocks of still images and blocks of moving images.

Furthermore, as described in Japanese Patent Application No. 60-268817, a variable-length method in which the word length (number of bits) changes depending on the dynamic range so that the maximum distortion that occurs when quantization is constant A coding method has been proposed.

In this variable length encoding method as well, the maximum distortion is set to be the same value for both a still image block and a moving block.

However, when the compression rate is increased by gradually increasing the quantization step, deterioration such as block distortion occurs in still images first. The reason for this is that in the case of images with relatively fast movement, fine details cannot be recognized due to the afterglow characteristics of the cathode ray tube and the integration effect of the human eye, and conversely, in the case of still images, fine details in the image cannot be recognized. This is because it is possible to recognize up to that point.

The present invention takes this visual characteristic into account and improves a high-efficiency encoding device using three-dimensional blocks. That is, in this invention, the amount of motion of an image is detected in block units, a motion code indicating the amount of motion is generated, and this motion code is used to perform encoding with a quantization step adapted to the amount of motion. Furthermore, it is an object of the present invention to provide a highly efficient encoding device that can increase the compression rate.

[Means for solving problems]

The present invention calculates the maximum value of a plurality of pixel data and the minimum value of a plurality of pixel data included in a block consisting of regions belonging to each of a plurality of consecutive fields of a digital image signal, and calculates a block from the maximum value and minimum value. a dynamic range detection circuit 4 that detects the dynamic range of each block, a motion amount detection circuit 3 that determines the amount of image movement for each block and generates a motion code SJ, and subtracts the minimum value from the values of a plurality of pixel data. and a subtraction circuit 5 for forming manual data after minimum value removal, and encoding the input data after minimum value removal within the detected dynamic range with a smaller number of quantization bits than the original number of quantization bits, a quantization circuit 8 in which a quantization step for encoding is adaptively determined in correspondence with the amount of motion given by a motion code; 17 et al. with additional code and encoding
□This is a highly efficient encoding device characterized by comprising means for transmitting a code signal and a discrimination code.

[Effect]

Since television signals have three-dimensional correlations in the horizontal, vertical, and temporal directions, in the stationary part, the range of change in the level of pixel data included in the same block is small. Even if the dynamic range of the data after removing the minimum level shared by the pixel data is quantized using fewer quantization bits than the original number of quantization bits, almost no quantization distortion occurs. By reducing the number of quantization bits, the data transmission bandwidth can be made narrower than the original one. Furthermore, in consideration of human visual characteristics, the quantization step of encoding is changed to adapt to the amount of image movement, and the compression rate can be increased.
Deterioration of images in static parts can be prevented.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. This description will follow the order of the items below.

a, Configuration of the transmitting side, Configuration of the receiving side C, Block and blocking circuit d, Motion amount detection circuit e, Dynamic range detection circuit f, Quantization circuit g, Modification a, Configuration of the transmitting side. , which shows the overall configuration of the transmitting side (recording side) of the present invention. For example, a digital television signal in which one sample is quantized to 8 bits is input to an input terminal indicated by l. This digital television signal is supplied to the blocking circuit 2.

The blocking circuit 2 converts the input digital television signal into a continuous signal for each block, which is a unit of encoding. The output signal of the blocking circuit 2 is supplied to a motion amount detection circuit 3 and a dynamic range detection circuit 4. The motion amount detection circuit 3 detects a three-dimensional block (in this example,
This circuit generates, for example, a 2-bit motion code SJ that indicates the amount of motion within (6 lines x 6 pixels x 3 frames).

As the amount of movement increases, the movement code SJ becomes (00).
It changes as (01), (10), and (11).

The dynamic range detection circuit 4 detects the maximum value M A X , the Jta minimum value MEN, and the dynamic range DR of each block. The input data converted into the block order from the blocking circuit 2 is supplied to the subtracting circuit 5,
In the subtraction circuit 5, data PDI from which the minimum value MIN has been removed is formed.

The motion code SJ from the motion amount detection circuit 3 is supplied to the quantization step determination circuit 6. Quantization step determination circuit 6
is a motion code S based on a nonlinear relationship that matches the visual characteristics.
A quantization step Δ corresponding to J is determined. This quantization step Δ is supplied to the bit number determining circuit 7. The bit number determining circuit 7 is supplied with the dynamic range DR from the dynamic range detecting circuit 4. In the bit number determination circuit 7, the dynamic range DR is divided by the quantization step Δ, and the value obtained by converting the division result into a binary number is set as the bit number Nb. This number of bits Nb is supplied to the quantization circuit 8.

Data PDI from the subtraction circuit 5 is supplied to the quantization circuit 8. The quantization circuit 8 performs encoding with a variable number of bits adapted to the dynamic range DR of each block. That is, the bit number Nb from the bit number determination circuit 7 is supplied to the quantization circuit 8, and the data PDI after minimum value removal is
is quantized by the number of bits Nb. This quantization circuit 8
The code signal DT from is supplied to the framing circuit 9.

In this embodiment, a motion code SJ, a small range DR, an i small value MIN, and a code signal DT are transmitted. These data are supplied to the framing circuit 9 and converted into transmission data. As for the form of the transmission data, each of the data portions consisting of the motion code SJ, the minimum value M[N, the dynamic range DR, and the code signal DT is encoded with an independent error correction code, and the parity of each error correction code is determined. You can use those that are added and transmitted. Further, each of the motion code SJ, dynamic range DR, and minimum value M TN other than the code signal may be encoded with an independent error correction code.

Furthermore, a common error correction code may be applied to both the motion code SJ, the range DR, and the minimum value M[H, and the parity thereof may be added. Transmission data is taken out to the output terminal IO of the framing circuit 9. Although not shown, the transmission data from the framing circuit 9 is transmitted as serial data (or recorded on a recording medium).

b. Receiving side configuration FIG. 2 shows the configuration of the receiving (or reproducing) side.

The received data from the input terminal 21 is sent to the frame decomposition circuit 22.
supplied to The frame decomposition circuit 22 separates the code signal DT, additional codes MIN and DR, and motion code SJ, and also performs error correction processing.

Code signal DT from frame decomposition circuit 22 is supplied to decoding circuit 25 . The motion code SJ is supplied to the quantization step determination circuit 23, and the quantization step determination circuit 23
The quantization step Δ is supplied to the bit number determining circuit 24, and the dynamic range DR is supplied to the bit number determining circuit 24.
supplied to

These quantization step determination circuit 23 and bit number determination circuit 24 have the same configuration as the quantization step determination circuit 6 and bit number determination circuit 7 on the transmitting side.

The decoding circuit 25 has the number of bits N together with the code signal DT.
b is supplied, and the variable length coded code signal DT is decoded. The decoding circuits 25 each perform a process opposite to that of the quantization circuit 8 on the transmitting side, and generate an output signal of a level corresponding to the code signal.

The output signal of the decoding circuit 25 is supplied to the adding circuit 26. In the decoding circuit 25, the data DTI after removing the 8-bit minimum level is restored as a representative level, and this data and the 8-bit minimum value MIN are added in the adding circuit 26, and the original pixel data is decoded. Output data of the adder circuit 26 is supplied to a block decomposition circuit 27. The block decomposition circuit 27 is a circuit for converting decoded data in the order of blocks into the same order as the scanning of the television signal, contrary to the blocking circuit 2 on the transmitting side.

At the output terminal 28 of the block decomposition circuit 27, the decoded original television signal is obtained.

C. Blocks and Blocking Circuits Blocks, which are units of encoding, will be explained with reference to FIG. In FIG. 3, reference numeral 14 indicates one block consisting of two-dimensional areas 14A, 14B, and 14c belonging to each of three frames, where solid lines indicate odd field lines and broken lines indicate even field lines. show. The area 14A is (6 lines x 6 pixels) by 6 pixels included in each of the 6 lines of each frame.

14B and 14C are configured. Therefore, lplot is
It consists of (6X6X3=108) pixels.

The total number of focuses of the original digital television signal contained within l block is (108 x 8 bits = 864 bits).

The smaller the number of quantization bits of the code signal, the better in order to suppress redundancy. However, in order not to increase quantization distortion, the number of quantization bits must not be reduced too much. When the number of quantization bits is 8 pinto, there are 256 possible levels of the television signal (0 to 255). However, in a stationary area other than an unsteady area such as the contour of an object, the level distribution of pixels in one block is concentrated in a fairly narrow level range. In the case of television signals, three-dimensional 1
Since each pixel within a block has a correlation, the Ginamiso clean range DR does not become very large in the stationary portion, and a maximum value of 128th is sufficient.

FIG. 4 shows an example of the configuration of the blocking circuit 2 described above. Input terminal 1 has frame memory 15A.

15B and 15C are connected in cascade. The pixel data of the current frame Fn÷2 is supplied to the scan conversion circuit 16A', and the pixel data of the previous frame Fn from the frame memory 15A is supplied to the scan conversion circuit 16A'.
+1 pixel data is supplied to the scan conversion circuit 16I3,
Pixel data of a previous frame Fn from frame memory 15A is supplied to scan conversion circuit 16C.

The scan conversion circuit 16A converts the order of data within one frame into the order of each block area, as shown in number 518. Similarly, the other scan conversion circuits 16I3.16C
Converts the order of data within a frame to the order of each block area. The output data of the scan conversion circuit 16A is supplied to the synthesis circuit 18 via the delay circuit 17A, and the output signal of the scan conversion circuit 16B is supplied to the synthesis circuit 18 via the delay circuit 17B. The delay circuit 17B has a delay amount equal to 72 pixel data included in two areas, and the delay circuit 17B has a delay amount equal to 36 pixel data included in one area. , a delay circuit and a switch circuit.

The output terminal 19 of the synthesis circuit 18 receives three consecutive frames Fn, Fn+l, Fn+2, as shown in the 51st page.
Pixel data of regions 14A, 14B, and 14C included in each of the regions 14A, 14B, and 14C are output in order. In other words, the output terminal 19 has
Output data converted to block order is obtained.

d. Motion amount detection circuit FIG. 6 shows an example of the motion amount detection circuit 3. In FIG. 6, 31A, 31B, and 31C each represent three frames F n , F n+1 . This is an input terminal to which image data of F n+2 is supplied. This input data is formed by parallelizing the output data of the aforementioned blocking circuit 2 block by block. The image data of each frame, the threshold data Tf from the terminal 31D, and the reset pulse PR from the terminal 31E are sent to the motion amount detection circuit 32A.

32B and 32C, respectively.

The motion amount detection circuit 32A detects image motion between the area 14A of frame Fn and the area 14B of frame Fn+1. The motion amount detection circuit 32B detects area 1 of frame Fn.
4A and the area 14C of frame F n+2. The motion amount detection circuit 32C detects the frame Fn
← Area 14B of 1 and area 14C of frame F n+2
Detect movement of images between. These motion amount detection circuits 3
2A, 32B.

32C has the same configuration except for the input image data, so FIG. 6 shows the specific configuration of the motion pre-detection circuit 1832A. Motion amount detection circuit 32A
, 32B, 32C multi-bit output signals. The output signal of the adding circuit 33 is supplied to the determining circuit 3.
4.

A 2-bit motion code SJ is taken out from the determination circuit 34 to an output terminal 35.

The motion amount detection circuit 32A includes a subtraction circuit 36. Absolute value conversion circuit 37. It is composed of a comparison circuit 38 and a totalization circuit 39. By the subtraction circuit 36 and the absolute value conversion circuit 37, the area 14
The absolute value of the level difference (frame difference) of the corresponding 100 pixels between A and region 1413 is formed. The comparator circuit 38 determines the absolute value of this frame difference as threshold data Tf.
compared to

A binary comparison output corresponding to the level relationship between the absolute value of the frame difference and the threshold data Tf is supplied to the aggregation circuit 39. The totaling circuit 39 totals the number of pixels exceeding the threshold value Tf. The counting circuit 39 is supplied with a reset pulse PR for each block.

Similarly to the above, the amount of motion between the regions 14A and 14c is detected by the motion amount detection circuit 32B, and the amount of motion between the regions 14A and 14c is detected by the motion amount detection circuit 32B.
The motion amount between 4C and 4C is detected by the motion amount detection circuit 32C. These motion amount detection circuits 32A, 32B, 32C
The amount of motion detected by each of these is supplied to the adding circuit 33. Therefore, the output signal of the adder circuit 33 has a value corresponding to the amount of motion of one entire block. The output signal of this adder circuit 33 is supplied to a determination circuit 34, which determines the amount of motion of the block and generates a 2-bit motion code SJ. This motion code SJ indicates whether the image of the block is a still image, an image with small movement, an image with intermediate movement, or an image with large movement.

In addition to this embodiment, methods for calculating the amount of motion include a method in which the maximum absolute value frame difference of the same pixel between frames is taken as the amount of motion, or a method of integrating the absolute value frame difference of the same pixel in framing. A method can be used in which the calculated value is used as the amount of movement.

e. Dynamic range detection circuit FIG. 7 shows the configuration of an example of the dynamic range detection circuit 4. As described above, the image data of the area that needs to be encoded is sequentially supplied to the input terminal 41 from the blocking circuit 2 for each block. Pixel data from this input terminal 41 is supplied to a selection circuit 42 and a selection circuit 43. The - selection circuit 42 selects and outputs the one with a higher level between the pixel data of the input digital television signal and the output data of the latch 44. The other selection circuit 43 selects and outputs the one with a smaller level between the pixel data of the input digital television signal and the output data of the latch 45.

The output data of the selection circuit 42 is supplied to the subtraction circuit 46 and is also taken into the latch 44 . The output data of the selection circuit 43 is supplied to the '$i calculating circuit 46 and the latch 48, and is also taken into the latch 45. A latch pulse is supplied to the latches 44 and 45 from the control section 49 .

Regulation? The ff11 unit 49 is supplied with timing signals such as a sampling clock and a synchronization signal that are synchronized with the input digital television signal from a terminal 50. The control unit 49 supplies launch pulses to the latches 44, 45 and launches 47, 48 at predetermined timing.

At the beginning of each block, the contents of latches 44 and 45 are initialized. All on latch 44.

Data of 0 is initialized, and the latch 45 contains all “
The lo data is initialized. The same, which is supplied sequentially, -
Among the pixel data of the block, the maximum level is latch 4.
It can be stored in 4. Furthermore, among the pixel data of the same block that is sequentially supplied, the minimum level is stored in the latch 45.

When the maximum level and minimum level detection is completed for one block, the maximum level of the block appears at the output of the selection circuit 42. - On the other hand, the minimum level of the block occurs at the output of the selection circuit 43.

When the detection for one block is completed, latches 44 and 45 are initialized again.

The dynamic range DR of each block is obtained from the output of the subtraction circuit 46 by subtracting the maximum level MAX from the selection circuit 42 and the minimum level MIN from the selection circuit 43. These dynamic range DR and minimum level MIN are latched in latches 47 and 48, respectively, by the fIII control block 49 latch pulse. The dynamic range DR of each block is obtained at the output terminal 51 of the latch 47, and the minimum value MIN of each block is obtained at the output terminal 52 of the latch 48.

f. Quantization circuit The quantization circuit 8 performs variable length encoding adapted to the dynamic range DR. FIG. 8 shows an example of the quantization circuit 8. In FIG. 8, a ROM indicated by 55 stores a data conversion table for converting the pixel data PDI (8 bits) after the minimum value has been removed because it is a compressed bit.

The number of bits Nb from the input terminal 56 to the ROM 55
and pixel data PDI from input terminal 57 are supplied as address signals.

In the ROM 55, a data conversion table is selected according to the number of bits Nb, and a code signal DT with the number of bits Nb is taken out to the output terminal 58. As described above, this number of bits Nb is obtained by dividing the dynamic range DR by the adoption step Δ set by the quantization step determining circuit 6 and converting it into a binary number. Therefore, the number of bits N
b is determined by both the quantization step Δ and the dynamic range DR.

For blocks of still images, the finest quantization is performed, for example, the maximum quantization is 4 (quantization step Δ=2E=8). In this case, the number of bits Nb changes within a range of 5 O pits. Therefore, the effective bit length in the code output from the ROM 55 changes. Valid bits are selected in the framing circuit 9.

FIG. 9 is used to explain variable length encoding performed by the above-mentioned quantization circuit 8 in the case (Δ=8).

This encoding is a process of converting pixel data from which the minimum value has been removed to a representative level.

The maximum allowable value of quantization distortion that occurs during this quantization (
This is called the maximum strain. ) is set to 4 as mentioned above.

FIG. 9A shows that the dynamic range DR is (maximum value MA
The case where the difference between X and the minimum value M r N is 8 is shown.

In the case of (DR=8), the center level 4 is set as the representative level LO, and (maximum 1 level=4). In other words, (O≦
DR≦8), the center level of the dynamic range is taken as the representative level, and there is no need to transmit quantized data. Therefore, the required number of bits Nb is zero. On the receiving side, decoding is performed using the minimum value M I N of the block and the dynamic range DR using the representative level LO as the restoration value.

FIG. 9B shows the case of (DR=17), where the representative levels are set as (LO=4) and (L1=13), respectively, and the maximum level is 1.
Snake becomes 4. Since there are two representative levels LO and Ll, (Nb=1).

In the case of (9≦DR≦17), it is (Nb mil).

The narrower the dynamic range DR, the smaller the maximum value is.

FIG. 9C shows the case of (DR=35), and the representative level is (LO=4) (L1=13) (L2=22) (L3=
31), respectively, and (E=4). Since there are four representative levels LO-L3, the number is (Nb-2). (
In the case of 1 day≦DR≦35), (Nb=2>).

In the case of (36≦DR≦71), 8 representative rehe/L
, (LQ to L7) are used. The ninth diagram is (DR=
71), and the representative level is (LO=4) (LL
=13)(L2=22)(L3=31)(L4=
40) (L 5 = 49) (L 6 = 58) (L
7 = 67). 8 representative level L
.

In order to distinguish between ~L7, (Nb=3) is set.

In the case of (72≦DR5143), 16 7-levels (LO-Ll5) are used. Figure 9E shows (DR=
143), and the representative level is (L 8 = 7
6) (L 9 = 85) (L 10 = 94) (L
11=103) (L12=112) (L13=121)
(L14=130) (L15=139) (LO to L7 are the same as the above values). In order to distinguish between the 16 representative levels (LO-L15), (Nb=4) is set.

In the case of (144≦DR≦287), 32 representative levels (LO to L31) are used. Figure 9F is (O
R=287), and the representative level is (L16=1
48) (L17=157) (Ll 8=166) (Ll
9=175) ... (L27=247)(
L28=256)(L29=265)(L30-274
)(L31=283) (LO=L15 is the same value as above). 32 representative levels (LO~L31
), it is assumed that (Nb=5). in fact,
Since the input pixel data is 8-bit quantized, the dynamic range DI'? The maximum value of is 255, and it cannot be quantized to representative hell (L28 to L31).

Furthermore, in a block where there is image movement, the quantization step Δ is made larger in response to the movement (2) and non-linearity. In other words, coarse quantization is performed, and the maximum value of the number of bits Nb is smaller than in the case of a stationary block.
The maximum value of b is made smaller. Therefore, the compression ratio can be increased compared to a method that always uses a constant quantization step (for example, 8) regardless of the amount of motion.

Television signals within one block are horizontal.

Since there is a two-dimensional correlation in the vertical direction and a three-dimensional correlation in the time direction, the level of pixel data included in the same block varies only small in the stationary portion. Therefore, the minimum level M shared by pixel data within a block
Even if the dynamic range of the data PDI after removing T N is quantized using a smaller number of quantization bits than the original number of quantization bits, almost no quantization distortion occurs. By reducing the number of quantization focuses, the data transmission bandwidth can be made narrower than the original one.

g. Modifications The present invention is applicable not only to variable length encoding systems but also to fixed length encoding systems. In the fixed-length encoding method, the dynamic range DR of a block is divided into a number of level ranges determined by the number of quantization bits, and a code signal corresponding to the level range to which data after minimum value removal falls is formed. Therefore, when the number of quantization bits for encoding a still block is set to 4 bits, the number of bits is set to be smaller depending on the amount of motion.

For example, regarding a stationary block, as shown in FIG. 10A, the level range to which the data PD■ after minimum value removal belongs is determined among the level ranges obtained by dividing the dynamic range DR into 16, and this determined level range is Generates the code signal shown. On the other hand, for a block with a small amount of motion, as shown in FIG. 10B, if the dynamic range DR is the same as that in FIG. P.D.
The level range in which I is included is determined. Therefore, if the quantization step for the stationary block is Δ, then the 10th
In the illustrated example, the quantization step for blocks with little movement is 2Δ.

In the above-mentioned quantization, as is clear from FIG. 10, the G dynamic range is equally divided by the quantization step Δ or 2Δ, and the representative level LO, L1, which is the central value of each region, is
．． ... is used as the value during decryption. This encoding method can reduce quantization distortion.

-”,!Small level M I N and maximum level MAX
Pixel data having each level always exists within one block. Therefore, in order to increase the number of encoded codes with an error of 0, divide the dynamic range DR into (2''-1) (where m is the number of quantization bits) and minimize the The level MIN may be set as the representative minimum level LO, and the maximum level MAX may be set as the representative maximum level L3.For simplicity, the example in FIG. 11 shows a case where the number of quantization bits is 2 bits.

In the above explanation, the code signal DT, dynamic range DR, minimum value M r N, and motion code SJ are transmitted. However, as an additional code, the dynamic range D
Instead of R, the basting step or the maximum distortion may be transmitted.

In addition, the l-block data is processed by a circuit that combines a frame memory, a line delay circuit, and a sample delay circuit.
They may be taken out at the same time.

〔Effect of the invention〕

According to this invention, the amount of data to be transmitted can be sufficiently reduced compared to the original data, and the transmission band can be narrowed. Further, the present invention has the advantage that in a steady region where the degree of change in tumor level is small, the original pixel data can be almost completely restored from the received data, and there is almost no deterioration in image quality. Furthermore, according to the present invention, since the dynamic range is determined for each block, the response is good at transient parts such as edges where the range of change is large.

In this invention, the quantization step for a stationary block or a block with a small amount of motion is made smaller than the quantization step for a block with a large amount of motion in consideration of human visual characteristics, so that the quality of the restored image on the receiving side is reduced. The number of bits of the code signal can be reduced without causing deterioration. Therefore, the compression ratio can be increased.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of the receiving side, FIG. 3 is a route diagram used to explain blocks that are units of encoding processing, and FIG. 4 5 is an example of the configuration of a blocking circuit and a route diagram for explaining the blocking circuit, FIG. 6 is a block diagram of an example of a motion amount detection circuit, and FIG. 7 is a block diagram of an example of a dynamic range detection circuit. 8 is a block diagram of an example of a quantization circuit, and FIG. 9 is a route diagram used to explain an example of quantization.
FIG. 1O and FIG. 11 are route maps used to explain another example of quantization and still another example, respectively. Explanation of main symbols in the drawings 1: Digital television signal input terminal, 2-block conversion circuit, 3: Motion amount detection circuit, 4: Dynamic range detection circuit, 6: Quantization step determination circuit,
7: Bit number determination circuit, 8: Quantization circuit, 9: Framing circuit. Agent Patent Attorney Tadashi Sugiura Figure 2 Figure 4 Figure 1 Figure 11 Figure 9 A Figure 9 B Figure 9 D] ``1 ■ -'' Figure 9 F

Claims (1)

[Scope of Claims] The maximum value of a plurality of pixel data and the minimum value of the plurality of pixel data included in a block consisting of regions belonging to each of a plurality of consecutive fields of a digital image signal are determined, and the maximum value and the minimum value of the plurality of pixel data are determined. means for detecting the dynamic range for each block from the minimum value; motion amount detection means for determining the amount of image movement for each block and generating a motion code; means for subtracting from a value to form input data after the minimum value has been removed; and encoding the input data after the minimum value has been removed within the detected dynamic range with a smaller number of quantization bits than the original number of quantization bits. and quantization means for adaptively determining the quantization step of the encoding in correspondence with the amount of motion given by the motion code; and at least one of the dynamic range information, the maximum value, and the minimum value. , two additional codes, a code signal obtained by the above-mentioned coding, and a means for transmitting the above-mentioned motion code.