JPH01140880A - Picture information transmitter - Google Patents

Abstract

PURPOSE:To reduce an error accompanied with encoding, and to make the deterioration of picture quality at the time of decoding inconspicuous by transmitting picture information after performing the coding considering a dynamic range in a block and the statistic distribution of each sample in the block. CONSTITUTION:A quantized NTSC television signal is inputted to a blocking circuit 12, and divided into the blocks consisting of the prescribed number of samples. A sample train rearranged by the blocking circuit 12 is impressed to a minimum value detector 14, a maximum value detector 16, an intra-block mean value detector 18 and delay circuits 20, 22, 24, 26. The outputs of the delay circuits 22, 24 are inputted to selection circuit 42, 44 and mean value detectors 48, 50. An encoder 36 generates the index of three bits per one sample, and the encoder 34 encodes at every block by considering its dynamic range and the statistic distribution of each sample, and outputs it to a transmission line.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image information transmission device that encodes and transmits image data in blocks.

[Conventional technology]

As a method for narrowing the transmission band of television signals, an encoding method is known in which the sampling frequency or the average number of bits per pixel is reduced. In the former encoding method, the 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 above, below or to the left or right of the interpolation point is indicated). A flag indicating whether the data is used is transmitted.

On the other hand, as one of the latter encoding methods, there is a block encoding method in which the screen within the l field is subdivided into minute blocks and encoded. In this encoding method, for example, the block of interest is quantized linearly or nonlinearly between its minimum and maximum values, an index indicating which quantization level it belongs to is transmitted for each pixel, and The minimum value and maximum value are transmitted as components.

[Problem that the invention seeks to solve]

In this conventional block encoding method, encoding is performed according to the dynamic range of pixel values within a block, but for example, when there is extreme brightness or darkness within a block, or when a block contains a boundary, etc. , when the distribution of pixel values is significantly different from the expected state, large distortion occurs in the decoded signal.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an image information transmission device that causes less decoding distortion when transmitting image information.

[Means for solving problems]

An image information transmission apparatus according to the present invention includes: a blocking means for dividing digital image data into blocks each consisting of a predetermined number of samples; and a first data forming means for forming at least two reference values regarding a dynamic range for each block. , a second data forming means for forming a plurality of types of situation data indicating the distribution situation of the sample values within the block, and based on two reference values of the first data forming means and a plurality of types of distribution situation data of the second data forming means. encoding means for encoding the intra-block samples to form encoded data;
The present invention is characterized by comprising a transmission data string forming means for forming a transmission data string using two reference values, a plurality of types of distribution situation data, and encoded data of each sample as transmission units.

[Effect]

By the above-mentioned means, the dynamic range within the block and the statistical distribution of each sample within the block are encoded and transmitted, so it is possible to form a code according to the situation of the image. Therefore, errors associated with encoding in image information transmission can be reduced, and deterioration in image quality during decoding can be made less noticeable.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a block diagram of a television signal encoding apparatus as an embodiment of the present invention. In Figure 1, 1
0 is an input terminal for a digital image signal. In this embodiment, an NTSC television signal in which one sample is quantized to 8 bits is input. The blocking circuit 12 edits the scanning order of the signal applied from the input terminal 10 in units of horizontal scanning lines within a block, and outputs the signal.

In the illustrated embodiment, one block consists of four samples in the horizontal direction and four lines in the vertical direction. The sample sequence rearranged by the blocking circuit 12 is sent to a minimum value detector 14 and a maximum value detector 16.
, intra-block average value detector 18 and delay circuits 20 and 22
, 24.26. Output M of minimum value detector 14
IN, the output MAX of the maximum value detector 16, and the output m0 of the average value detector 18 are applied to encoders 34 and 36.

The comparator 38 compares each sample in the block delayed by the delay circuit 20 with the average value m0 from the average value detector 18, and outputs 1 when it is greater than 10 and outputs O when it is less than 1IIO. 40 is a cluster ring memory with a capacity of 16 bits, and 1 per sample.
The comparison result of the comparator 38 for one block of bits is stored and used as a gate pulse to the selection circuit 42 and 44.
When it is "1", it outputs "H", and when it is "0", it outputs rLJ. A signal inverted by an inverter 46 is applied to the selection circuit 42 . That is, the selection circuit 42 is the delay circuit 22
Among the outputs of , only samples below m0 (subblock 1
), and the selection circuit 44 passes only samples larger than mo (subblock 2) among the outputs of the delay circuit 24. The mean value detector 48 detects the mean value m of the samples in sub-block 1 and sends it to the encoder 34.36.
The average value detector 50 detects the average value mz of the samples in sub-block 2 and applies it to the encoder 34.36.

The output DT of the delay circuit 26 is applied to the encoder 36 as is. Note that the delay circuits 20 to 26 are connected for the purpose of timing adjustment. The encoder 36 forms an index ID of 3 bits per sample from each input signal so, m8m, MIN, MAX, DT, and applies it to the encoder 34. For each block, the encoder 34
A code string to be described later is outputted from the output terminal 52 to a transmission path (not shown).

FIG. 2 shows a specific example of the configuration of the encoder 36.

In this embodiment, as shown in FIG. 5, between MIN and m, between m and mo, between mo and m, and between m2 and MAX.
Each section is divided into two equal parts, and each sample is encoded using these eight sections. Therefore, the index ID that specifies the section to which it belongs may be 3 bits.

In FIG. 2, subtractor 130 subtracts M from sample value DT.
subtracter 132 subtracts MIN from 1;
The subtracter 134 subtracts m+'t- from mo, and the subtracter 13
6 subtracts MIN from mo, subtractor 138 subtracts mo from m2, subtractor 140 subtracts MIN from m2, and subtractor 142 subtracts m2 from MAX.

Dividers 144, 145, 146, and 147 respectively set the outputs of subtracters 132, 134, 138, and 142 to 172, and adder 148 sets the output of divider 145 to 172.
adder 149 adds the output of subtracter 136 to the output of divider 146, adder 150 adds the output of divider 1
The output of the subtracter 140 is added to the output of the subtracter 47. One of the comparison circuits 151 to 157 is connected to a divider 1, respectively.
44 output (1/2) (mt-old N), subtractor 132
output (mt-MIN), output of adder 148 (mt-MIN),
MIN) + (1/2) (mo-cocoon, ), subtractor 136
output (me-MIN), output of adder 149 (no-
MIN)+(1/2)(mz-mo), the output of the subtracter 140 (lz-MIN) and the output of the adder 150 (mt-
MIN) + (1/2) (MAX-mz) is applied, the other input is input, and the output of the subtracter 130 is DT'' (=DT
-MIN) is applied.

Assuming that the outputs of the comparators 151 to 157 are 01 to C7, the results are as follows depending on each case.

(1) O≦DT'<(1/2) (mt-MIN)C1
=C2=C3=C4=C5・C6=C7=0(2)
(1/2) (mt-MIN)≦DT'<m, -MINC
1=1. C2=C3, C4=C5・C6=C7・0(
3) n+-MIN≦DT'<(1/2) (ffIo
-mt)+(mt-MIN)C1=C2=1, C3
=C, bc5. c6=c7=0(41(1/2)(Il
o-mυ+(mt-MIN)≦DT'<m, -MINc
l=c2=c3=1. c4=c5=c6=c7=0(
5) m o −M I N ≦ DT'< (1/2)
(Town - m.) + 1° - Gate IN) C1 = C2 = C3 = C4
=1, C3=C6=C7=0(6) (1/2)
(fflz-no)+ (mo-MIN)≦DT'<
mz-MZNCbC2・C3・C4=C5・1. C6=
C7・0(7)mt-MIN SDT'<(1/2)
(MAX-mz)+(llz-MIN)C1=C2=C
3=C4, C3=C6=1, C7=0(81(
1/2) (MAX-mz) + (mz-MIN) ≦
DT'<MAX-MINC1=C2=C3=C4=C
5, C6-C7-1 priority encoder 158
is (000) for (1) above, (000 for (2))
1), (010) when (3), (01 when (4))
1), (5) (100), (6) (1
01), (7) (110), (81 (1
11) Outputs the 3-bit index ID. This index ID is applied to encoder 34.

As shown in FIG. 6, the encoder 34 outputs MIN, MAX, m++RIo, 1IIz+! It is outputted to the output terminal 52 in units of D. In this example, M
IN, MAX.

By configuring 11++mo+IIz with 8 bits each and 10 with 3 bits per sample, the compression ratio is 887 when compared when all sample values are transmitted in 8 bits.
12 days can be achieved.

FIG. 3 shows a schematic configuration of a decoding device corresponding to the encoding device of FIG. 1. A digital television signal input from a transmission line (not shown) is applied to the data separation circuit 62 from the input terminal 60, and the signal is MIN+MAX+ff1o+11111.
111! The signal is separated into IID and supplied to the decoder 64.

The output of decoder 64 is M for each pixel in the block.
Since this value corresponds to the difference from the IN level, the adder 66 adds MIN to compensate for the MIN level, and then outputs it to the output terminal 68. Each pixel value is obtained from the output terminal 68.

FIG. 4 shows details of the decoder 64. The subtractor 270 is I
MIN is subtracted from II, and the subtracter 271 subtracts m from mo,
The subtracter 272 subtracts MIN from mo, and the subtracter 273 subtracts MIN from m. , and the subtracter 274 subtracts r
MIN is subtracted from a2, and the subtracter 275 subtracts - from MAX.
Subtract. The divider 276 outputs the output of the subtracter 270 (++
++-MIN) is set to 174, and the divider 277 is set to 3/4. The divider 278 receives the output of the subtracter 271 (mo-mt
) is set to 174, and the divider 279 is set to 3/4. The adder 280 adds the output of the subtracter 270 to the output of the divider 278, and the adder 281 adds the output of the subtracter 27 to the output of the divider 279.
Add the output of 0. The divider 282 sets the output (mZ-mo) of the subtracter 273 to 174, and the divider 283 sets the output (mZ-mo) to 3/4.
Make it. Adder 284 adds subtracter 2 to the output of divider 282.
The adder 285 adds the output of the subtracter 272 to the output of the divider 283.

Furthermore, the divider 286 outputs the output (MAX-m
, ) are set to 174, and the divider 287 is set to 3/4. The adder 288 adds the output of the subtracter 274 to the output of the divider 286 (
m, -MIN), and the adder 289 adds the divider 287
The output of the subtracter 274 is added to the output of the subtracter 274.

The selection circuit 290 follows the index 10 and the divider 27
6.277 and adders 280, 281, 284.285
, 288, 289. Specifically, the output of the selection circuit 290 is r 1/4(mt-MI
N) J, r3/4 (m, -MIN) J, rl/4 (
me-mt) + (mt-MIN) j, r 3/4 (
mo-mυ+(mt-MEN) J, r 1/4(mt
-mo) + (mo-MIN) J, r 3/4 (mz-
mo) + (mo-MIN) J, r 1/4 (MAX
-mz) + (mz-MIN) J and r3/4(M
AX-mz) + (mz-MIN)j. This output is applied to adder 66.

As explained above, in this embodiment, by encoding and transmitting a digital television signal according to the level distribution of each sample value within a divided block, even if the amount of information is small, deterioration in image quality etc. It can be encoded and transmitted in a state with fewer errors.

In this example, the index ID, MIN, M^X+
The configuration was configured to send ff1O+mI+mt, but MIN
, MAX, one of them and the dynamic range DR may be sent. Also, the number of average values is m
It is not limited to the three types of O+ll1l+m2. ” O+
m I + m z may be determined based on a histogram of sample values within the block.

〔Effect of the invention〕

As can be easily understood from the above description, according to the present invention, encoding is performed taking into account not only the dynamic range but also the statistical distribution of pixels within a block, so that encoding distortion is less likely to occur.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the configuration of an encoding device as an embodiment of the present invention, FIG. 2 is a detailed diagram of the encoder 36 in FIG. 1,
3 is an example of the configuration of a decoding device, FIG. 4 is an example of the configuration of the decoder 64 shown in FIG. This is an example of the output code string.

Claims (1)

[Claims] blocking means for dividing digital image data into blocks each consisting of a predetermined number of samples; first data forming means for forming at least two reference values regarding dynamic range for each block; A second data forming means for forming a plurality of types of situation data encodes the samples in the block based on the two reference values of the first data forming means and the plurality of types of distribution situation data of the second data forming means, and generates encoded data. and a transmission data string forming means that forms a transmission data string using the two reference values, the plurality of types of distribution status data, and the encoded data of each sample by the first data forming means as transmission units. An image information transmission device characterized in that: