JP2000023156A - Image encoder, encoding method and image decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image encoding method for minimizing encoding degradation and keeping high image quality even in the case that the data rate of image data is high and a data amount is large. SOLUTION: A data number for one screen of the input image data of a successive scanning system is thinned to a half and they are converted into the image data of an interlaced scanning system. The image data after change are encoded by the unit of one screen in an encoding part 1. In an image data number restoration means 33, the encoded image data are decoded and the restored image data of the successive scanning system same as the input image data are generated from the decoded image data by using an interpolation processing. The delay error of the restored image data and the input image data is corrected by a delay circuit 35. The difference data of the restored image data from the image data number restoration means and the input image data from the delay circuit 35 are generated in a difference computation means 34 and the difference data from the difference computation means 34 are encoded by the unit of one screen. The encoded image data encoded in the encoding part 1 and encoded difference data are turned to encoded output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention encodes progressive scan image data in which the number of image data per unit time is twice that of interlaced scan image data, and interlaced scan image data. The present invention relates to an image encoding device, an image encoding method, and an image decoding device that can perform encoding with high efficiency without causing deterioration of encoding as much as possible.

[0002]

2. Description of the Related Art When image data is recorded on a recording medium such as a disk and reproduced, or transmitted by terrestrial television broadcasting, satellite television broadcasting, cable television broadcasting, and the like.
When image data is transmitted through a transmission medium having a limited transmission capacity, the image data is compressed and transmitted in order to effectively use the limited transmission capacity.

FIG. 9 shows a block diagram of an image coding circuit of the MPEG system which has been widely used as this type of compressed image coding system.

[0004] Input digital image data Vi is image data of an effective screen portion from which a synchronization signal portion has been removed. The input digital image data Vi is supplied to the pre-processing circuit 11 of the encoding unit 1, where the image order for performing the motion compensation processing is changed, and the raster scan is converted into a block scan. That is, in this example, raster scan format image data in units of horizontal scanning lines is converted into block scan format image data in units of blocks of, for example, horizontal × vertical = 8 pixels × 8 pixels.

The block scan format image data from the preprocessing circuit 11 is supplied to a DCT processing circuit 13 through a subtraction circuit 12 for calculating a difference in inter-frame or inter-field prediction encoding processing. The DCT processing circuit 16 converts a signal in the time domain into a DCT in the frequency domain for data in blocks BL (a prediction error signal in a P picture and a B picture to be subjected to inter-frame predictive coding).
A DCT operation for converting into a coefficient is performed.

[0006] The DCT coefficient as a result of the arithmetic processing by the DCT processing circuit 13 is supplied to a quantization circuit 14 and quantized. The output of the quantization circuit 14 is supplied to the variable length encoding circuit 2 as an output of the encoding unit 1 and to a circuit unit for motion compensation processing.

That is, the output of the quantization circuit 14 is returned to the original difference information by the inverse quantization circuit 15 and the inverse DCT processing circuit 16 for the motion compensation processing,
7 is supplied. The prediction data of the corresponding block of the previous frame (or previous field) from the motion compensation circuit 19 through the switch circuit 21 is supplied to the addition circuit 17 to obtain the prediction data of the current frame (or previous field). Can be That is, the locally decoded data is obtained from the adding circuit 17, and the locally decoded data is stored in the frame memory 18.

A motion vector detecting circuit 20 calculates a motion vector for generating a predicted image signal by performing motion compensation in a motion compensating circuit 19 from the image data from the preprocessing circuit 11 and the image data in the frame memory 18.

The motion compensation circuit 19 includes a frame memory 18
, Using the motion vector from the motion vector detection circuit 20 for the locally decoded image data stored in
The motion compensation is performed, and the subtraction circuit 12 generates a predicted image signal of the next frame supplied from the preprocessing circuit. And
The predicted image signal is supplied to the subtraction circuit 12 through the switch circuit 21.

The switch circuit 21 is connected to the terminal a and supplies the output of the motion compensation circuit 19 to the subtraction circuit 12 when performing inter-frame predictive coding according to a switching control signal from a control circuit (not shown).

In the block for performing the intra-frame encoding process, the switch circuit 21 is switched to the terminal b side.
The data supplied to the subtraction circuit 12 is set to zero. That is, in this case, the subtraction circuit 12 does not perform the difference calculation.

The image data compressed and encoded by the encoding unit 1 as described above is subjected to variable-length encoding using, for example, Huffman code in a variable-length encoding circuit 2 to control the transmission amount. Is output as output data Vo through the buffer memory 3.

The rate control circuit 4 monitors the data occupation state of the buffer memory 3 and controls the quantization value of the quantization circuit 14 according to the detected data occupation state. As a result, the output transmission rate of the output image data Vo is stabilized, and the output image data Vo is controlled so as to effectively utilize the transmission capacity.

Although not shown, information on the motion vector detected by the motion vector detection circuit 20 is transmitted together with the encoded output data Vo.

[0015]

Recently, high-definition, high-quality television broadcasting such as satellite television broadcasting and terrestrial digital television broadcasting has become a reality. The number of horizontal lines per frame of this type of television broadcast is 1125, of which the number of effective horizontal lines is 10
The number is 80. As a scanning method (scanning method), there are two methods: an interlaced scanning method and a sequential scanning method.

In the interlaced scanning system, the field rate is set to 60 Hz and the frame rate is set to 30 Hz. If the interlaced scanning image data is used, the image coding apparatus shown in FIG. It is possible to perform compression encoding with image quality secured.

On the other hand, in the progressive scanning system, the frame rate is 60 Hz, and the transmission data rate is doubled. Therefore, when compression encoding is performed using the image encoding apparatus of FIG. 9, it is necessary to compress the image data at a higher compression ratio than the interlaced scanning image data. As a result, there is a possibility that more coding degradation will occur and image quality will be degraded than in the case of encoding interlaced image data.

In view of the above, the present invention increases the transmission capacity of a transmission medium (transmission path) even in the case of progressive scanning image data with a frame rate of 60 Hz and 1080 effective horizontal lines. It is an object of the present invention to provide an image coding apparatus and method capable of minimizing deterioration of image quality without causing any deterioration.

[0019]

According to a first aspect of the present invention, there is provided an image encoding apparatus for encoding input image data in units of one screen. Image data number reduction means for thinning out the data amount of one screen of the input image data; and image data from the image data number reduction means in units of one screen,
Image encoding means for encoding; decoding means for generating decoded image data obtained by decoding the encoded image data; and decoding the decoded image data from the decoding means by interpolation using the input image. Image data number restoring means for converting the number of data into the same number of restored image data; andthe input image data for correcting a delay error between the restored image data from the image data number restoring means and the input image data. Delay means for delaying, the image data from the image data number restoring means, difference calculation means for generating difference data between the input image data from the delay means, and the difference data from the difference calculation means, A difference data encoding unit that encodes in units of one screen; encoded image data in units of one screen from the image encoding unit; Of the coded difference data for the image data of the same screen as the encoded image data, characterized in that it comprises and output means for outputting for transmission.

In the first invention, when the input image data is image data of a progressive scanning system, the image data number reducing means outputs one of the input image data.
It is preferable to extract image data every horizontal line and output image data corresponding to the image data of the interlaced scanning method by changing the position of the horizontal line to be extracted in adjacent frames.

According to the first aspect of the present invention, the image data number reduction means reduces the data of horizontal lines every other horizontal line, for example, and converts the image data corresponding to the image data of the interlaced scanning method to the image data. The image data is supplied to the image encoding means, and is encoded in units of one screen of the image data of half the number of data. Therefore, the image encoding means can handle image data of the same transmission rate as image data of the interlaced scanning method even in the case of image data of the progressive scanning method.

In the first invention, as for the information of the remaining half of the image data of one screen unit which is not encoded by the image encoding means, the image data encoded by the image encoding means is decoded. The difference data between the restored image data restored from the image data by using the interpolation process and the corresponding input image data is reflected, and the difference data is encoded.

The image data encoded by the image encoding means and the difference data are transmitted as output data. In this case, since the difference data has a smaller data amount than the thinned-out interlaced scanning image data, the difference data has a smaller code amount than the case where the sequential scanning method input image data is directly encoded by the image encoding means. The degradation is significantly reduced, and the degradation of image quality can be minimized.

An image encoding apparatus according to a second aspect of the present invention is an image encoding apparatus for encoding input image data in units of one screen, wherein the number of data of one screen of the input image data is The image data number reduction means for thinning out the half, and the image data from the image data number reduction means,
Image encoding means for encoding in units of one screen; and data corresponding to the data decimated by the image data number reducing means, from image data obtained by decoding the image data encoded by the image encoding means. Interpolated image data generating means generated by interpolation processing, and delay means for delaying the input image data to correct a delay error between the interpolated image data from the interpolated image data generating means and the input image data, Difference calculation means for generating difference data between the interpolation image data from the interpolation image data generation means and image data corresponding to the interpolation image data among the input image data from the delay means, and the difference calculation means Data encoding means for encoding the difference data from the image data in units of one screen, and an encoded image in units of one screen from the image encoding means And output means for outputting, from the difference data encoding means, encoded difference data on image data on the same screen as the encoded image data for transmission. .

In the second aspect of the present invention, the data whose number of data has been decimated to half by the image data number reducing means is supplied to the image encoding means, and one screen of the image data of the half data number is provided. The image data is encoded in units of minutes, and the image encoding means can handle image data of the same transmission rate as image data of the interlaced scanning method, even in the case of image data of the progressive scanning method.

In the case of the second invention, the method of calculating the difference data for the information of the remaining half of the image data of one screen unit which is not encoded by the image encoding means is different from that of the first invention. .

That is, in the case of the second invention, only the image data corresponding to the thinned image data is
It is generated by interpolation image data generation means by interpolation processing. Then, a difference between the image data corresponding to the thinned image data of the corresponding input image data and the interpolated image data generated by the interpolated image data generating means is calculated to generate difference data.

In the second embodiment, the difference calculation is not performed on half of the image data for one screen encoded by the image encoding means. The difference data is reduced by that much,
Coding deterioration is further reduced, and deterioration of image quality can be minimized.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image coding apparatus according to the present invention will be described below with reference to the drawings. In the embodiment described below, the number of horizontal lines per frame is 1125, and the number of effective horizontal lines is 108
This is a case where image data HVi of 0 lines and of a progressive scanning method with a frame rate of 60 Hz is compression-coded by the MPEG method.

[First Embodiment] The input image data HVi of the progressive scanning method is supplied to an image data number reduction circuit 31. The image data number reduction circuit 31 reduces the number of image data of the input image data HVi and reduces the transmission rate. In the case of this example, the image data of every other horizontal line is extracted, and the remaining image data of every other horizontal line is thinned out. In addition, in adjacent frames, the horizontal line position to be extracted is made different, and processing is performed so that the data rate in pixel data units is half that of the original input image data HVi of the progressive scanning method.

That is, in the case of this example, the image data number reducing circuit 31 applies a filter of the vertical low-pass characteristic in the image frame of the progressive scanning system, and then, for example, the image data HVi of the input progressive scanning system. Among them, odd lines are thinned out in odd frames, and even lines are thinned out in even frames. Thereby, the progressive scan image data at the frame rate of 60 Hz is converted into the interlaced scan image data at the frame rate of 30 Hz. Therefore, the image data number reduction circuit 31 in this example performs sequential-to-interlaced scan conversion to reduce the number of image data and the data rate to half.

In the image data number reduction circuit 31 in order
The interlaced scan conversion processing will be described with reference to FIGS.

In FIG. 2A, circles arranged in the vertical direction indicate horizontal lines of one frame. That is, for example, A0, A1, A2,... Indicate each horizontal line of the frame A, and B0, B1, B2,.

In the image data number reduction circuit 31, FIG.
As shown in (B), in frame A, only the image data of every other horizontal line A0, A2, A4,... Is extracted, and in frame B, every other horizontal line B1, B3 at a different position is extracted. , B5,... Are extracted. In the frame C, only the image data of every other horizontal line C0, C2, C4,... Hereinafter, the image data is extracted while changing the horizontal line position to be extracted.

As a result, the frame rate 6 shown in FIG.
As shown in FIG. 2B, image data IVi equivalent to the image data of the interlaced scanning method having a field rate of 60 Hz and a frame rate of 30 Hz can be obtained from the 0 Hz progressive scanning image data.

As described above, the number of image data obtained from the image data number reduction circuit 31 is reduced to half, and the image data IVi converted into the interlaced scanning format is supplied to the encoding unit 1. This encoding unit 1 has exactly the same configuration as the encoding unit 1 shown in FIG. 9, and as described above, compresses and encodes the image data input thereto according to the MPEG method.

In this case, the processing speed of the encoding unit 1 is:
This is half the speed in the case of encoding the image data HVi of the progressive scanning method directly, and this is because the frame rate is 3
The processing speed is the same as that when encoding image data of 1080 effective scanning lines of the interlaced scanning method at 0 Hz and a field rate of 60 Hz.

The image data compressed and encoded by the encoding unit 1 as described above is supplied to the variable length encoding circuit 2 in the same manner as in FIG. The data is subjected to long coding and output as output data HVo through a buffer memory 3 for controlling the transmission amount. Then, the buffer memory 3 is controlled by the rate control circuit 5.
And controls the quantization value of the quantization circuit 14 according to the detected data occupation state. As a result, the output transmission rate of the output data HVo is stabilized,
It is controlled so as to effectively utilize the transmission capacity.

As described above, information on half the image data of the input image data HVi of the progressive scanning method is compression-encoded and transmitted as output data HVo. On the other hand, information relating to the remaining half of the input image data HVi that is not included as information in the output data HVi is encoded as a small information amount and transmitted as described below.

The image information has a feature that the correlation in the horizontal direction and the correlation in the vertical direction, and furthermore, the correlation in the frame unit is strong. Therefore, at the time of decoding the coded and transmitted image data, the information thinned out by the image data number reduction circuit 31 can be generated by an interpolation process using the correlation therebetween. Therefore, decoded image data of a certain image quality can be obtained without transmitting the remaining half of the input image data HVi that is not included as information in the output data HVo.

However, in this embodiment, in order to further improve the image quality, the difference between the image data generated by interpolation from the output data HVo and the input image data HVi is further transmitted. With this configuration, on the decoding side, image data close to the original input image data HVi can be restored by adding and combining the difference data with the decoded image data generated by interpolation from the output data HVo. . For this reason, in the first embodiment, the following is performed.

First, the local decoded signal obtained from the adding circuit 17 of the encoding unit 1 is supplied to the frame memory 18 and also to the post-processing circuit 32. The post-processing circuit 32 performs a process reverse to the pre-processing performed by the pre-processing circuit 11 of the encoding circuit 1. The post-processing circuit 32 converts the data in the block scan format into the data in the raster scan format. Is performed. This post-processing circuit 32
Is supplied to the image data number restoration circuit 33.

The image data number restoring circuit 33 restores the image data, which has been thinned out by the image data number reducing circuit 31, by interpolation processing, and sequentially scans the same image data and the same data rate as the input image data HVi. Is a circuit for restoring the image data. In this case, it is a circuit for performing a skip-to-sequential scan conversion process.

In the case of this example, the image data number restoring circuit 33 includes a frame memory, detects a motion vector between the previous frame and the frame, and uses only the data of the frame as an interpolation processing means. A first interpolation unit to be used; and a second interpolation unit using data of a previous frame stored in the frame memory.
Then, the image data number restoration circuit 33 adaptively switches between the first interpolation means and the second interpolation means according to the detected motion vector.

FIG. 3 is a block diagram of a configuration example of the image data number restoring circuit 33 in this embodiment.

The image data from the post-processing circuit 32 is supplied to the synthesizing circuit 331 and also to the average value interpolation data generating circuit 332, the previous frame data transmitting circuit 333 and the motion vector detecting circuit 334.

In the example of FIG. 3, the first interpolation means is constituted by an average value interpolation data generation circuit 332, and the image data of each line of the image data inputted thereto is
The average value of the image data of the upper and lower lines is calculated, and the calculated value is output as interpolation data.

The second interpolation means is constituted by the previous frame data transmission circuit 333. The previous frame data sending circuit 332 includes a frame memory FL, and sequentially reads out pixel data of the previous frame corresponding to pixel data of the frame from the frame memory FL.

The output data of the average value interpolation data generation circuit 332 and the output data of the previous frame data transmission circuit 333 are supplied to one and the other input terminals of the switch circuit 335, respectively. The switch circuit 335 is adaptively switched according to the magnitude of the motion vector, as described later, according to the switching signal from the interpolation adaptive switching circuit 336. Then, the output data of the switch circuit 335 is supplied to the synthesizing circuit 331, and is synthesized with the image data from the post-processing circuit 32, whereby the interpolation processing is executed.

The motion vector detection circuit 334 detects a motion vector from the image data from the post-processing circuit 32 and the image data of the previous frame in the frame memory FL. Then, the motion vector detection output is output to the interpolation adaptive switching circuit 3.
36.

Then, the interpolation adaptive switching circuit 336 selects the second interpolation means in an image portion in which the motion between the previous frame and the frame is not detected or is very small and a still image portion is detected. Then, the switch circuit 335 is switched so as to select the data from the previous frame data transmission circuit 333, and the interpolation is performed by using the data of the previous frame stored in the frame memory FL as it is as the thinned image data. I do.

The interpolation adaptive switching circuit 336 selects the first interpolation means in a portion where the motion between the previous frame and the frame is detected to be relatively large, and selects the average value interpolation data generation circuit 332. The switch circuit 335 is switched so as to select the interpolation data generated as the average value of the image data of the upper and lower lines as the data of the line subjected to the thinning processing from the above, and execute the interpolation processing.

Thus, the restored sequential scan image data RVi corresponding to the input image data HVi is obtained from the image data number restoring circuit 33. This restored progressively scanned image data R
Vi can be represented as shown in FIG.

In FIG. 2C, horizontal lines A0, A2, A4,..., B1, B3, B5,.
.., C0, C2, C4,.
(B) is obtained by decoding the interlaced image data IVi, and if there is no coding deterioration in the coding unit 1, these original horizontal lines A0 and A
2, A4, B1, B3, B5, C0, C
The image data of 2, C4,... Correctly returns to the original without coding deterioration.

In FIG. 2C, horizontal lines a1, a3, a5,..., B0, b2, b4
.., C1, c3, c5,... Are image data generated by interpolation processing. This interpolated image data has an interpolation error between the input image data HVi and the corresponding image data.

As described above, the image data number restoration circuit 3
The restored progressively scanned image data RVi generated in 3 is supplied to the subtraction circuit 34.

On the other hand, the input progressively scanned image data HVi is
After being delayed by the delay circuit 35, it is supplied to the subtraction circuit 34. The delay circuit 35 includes the encoding unit 1 and the post-processing circuit 32.
In addition, a delay corresponding to the processing delay time in the image data number restoring circuit 33 is performed, and the timing of the image data RVi from the image data number restoring circuit 33 and the input image data HVi are aligned.

Therefore, the subtraction circuit 34 outputs the restored sequential scan image data RVi generated by the image data number restoration circuit 33 and the input image data HVi of the corresponding frame.
Is obtained as difference data DF. This difference data DF
Is a difference between all the pixel data of the input image data HVi and the restored sequential scan image data RVi.
Therefore, the difference data DF includes pixel data generated by interpolation (in the above-described example, line-by-line pixel data because line thinning is performed) and input image data HVi
Not only the difference from the corresponding pixel data but also the encoding unit 1
When an encoding error occurs in the above, the encoding error is included.

FIG. 4 is a diagram schematically showing this difference calculation. FIG. 4 shows a case where the difference data DF does not include a coding error.

After the difference data DF is quantized by the quantization circuit 36, the variable length coding circuit 37 performs variable length coding using, for example, Huffman code. The difference data Dfo variable-length coded by the variable-length coding circuit 37 is output as difference output data Dfo through a buffer memory 38 for controlling the transmission amount.

The rate control circuit 5 includes a buffer memory 38
And controls the quantization value of the quantization circuit 36 according to the detected data occupation state. As a result, the output transmission rate of the difference data is stabilized, and control is performed so as to effectively utilize the transmission capacity.

Although not shown, information on the motion vector detected by the motion vector detection circuit 20 is transmitted together with the encoded output data HVO.

As described above, in the first embodiment, half the data amount of the progressive scanning image data and half the data rate of the interlaced scanning image data IVi at a data rate of 1/2 are encoded. The output image data HVo compressed and encoded by the unit 1 and the differential data Dfo between the input image data and the progressive scan image data restored by interpolation from the decoded data of the compressed encoded data are transmitted. Like that.

For this reason, the encoding unit 1 uses the interlaced scanning method with a field rate of 60 Hz and a frame rate of 30.
Encoding is performed in exactly the same way as in the case of image data of Hz. Therefore, the coding degradation is the same as that of the image data of the interlaced scanning method with the field rate of 60 Hz.

The information of the image data which has been thinned out because it has been converted into the image data of the interlaced scanning system is reflected on the difference data DFo and transmitted. Therefore, as the image information to be transmitted, it is equivalent to transmitting all information about the original image data of the progressive scanning method, and a high-quality reproduced image can be obtained.

The difference data DFO has a very small amount of transmission data. Therefore, this difference data DFO
However, even if it is multiplexed with the output image data HVo and transmitted, the increase in the transmission load is small.

As described above, according to the first embodiment, it is possible to realize image coding that maintains high image quality while minimizing coding deterioration.

Then, in the image data number restoring circuit 33,
Since the interpolation processing is adaptively switched, the data amount of the difference data DF is minimized, and it can be expected that the increase in the transmission data amount is minimized.

In the above description, the difference data is quantized as it is.
Of course, compression encoding may be performed by using a CT process or the like.

In the above description, the motion vector detecting circuit for adaptively switching between the first interpolation means and the second interpolation means in the image data number restoring circuit 33 is the image data number restoring circuit 33. However, since the delay circuit 35 also includes a frame memory, the delay circuit 35
, A motion vector detecting circuit may be provided, and its detection output may be supplied to the interpolation adaptive switching circuit 336 of the image data number restoring circuit 33.

[Example of Decoding Apparatus] Image data encoded and transmitted by the above-described image encoding apparatus is decoded as follows. That is, FIG. 4 shows a block diagram of an embodiment of the image decoding apparatus.

As shown in FIG. 5, the encoded image data HV
o is the variable length decoding circuit 4 through the buffer memory 41
2 for variable length decoding. The image data variable-length decoded by the variable-length decoding circuit 42 is supplied to an inverse quantization circuit 43, where it is inversely quantized. The inversely quantized image data is subjected to a frequency domain DCT by an inverse DCT circuit 44.
The coefficients are returned to the image data of the block unit in the time axis region (difference information at the time of the inter-frame prediction coding part such as a P picture and a B picture) from the coefficient. This inverse DCT circuit 44
Is supplied to the addition circuit 45.

The addition circuit 45 includes a switch circuit 48
, The prediction data of the corresponding block of the previous frame from the motion compensation circuit 47 is supplied, and the prediction data of the current frame is obtained. That is, predictive decoded data is obtained from the adding circuit 45, and the predicted decoded data is stored in the frame memory 46. In the I picture and the non-predictive coding part, the switch circuit 48 is connected to the opposite side from the illustrated side, and no prediction data is supplied to the adding circuit.

The motion compensation circuit 47 includes a frame memory 46
The motion compensation is performed by using the prediction decoded image data and the motion vector information included in the transmission data and supplied to the motion compensation circuit 47, and the output is used as the prediction data by the addition circuit. 45.

The decoded data obtained from the adder circuit 45 is not progressive scan image data, but
This is the image data of the interlaced scanning method in which the number of lines is reduced to 1/2. The decoded data from the adding circuit 45 is supplied to a post-processing circuit 49.

In the post-processing circuit 49, the data in the block scan format from the adder circuit 44 is converted into the data in the raster scan format, and the image order is restored. The output data of the post-processing circuit 49 is supplied to the image data number restoration circuit 50.

The image data number restoring circuit 50 has the same configuration as that of the image data number restoring circuit 33 of the image encoding apparatus of FIG. 1, and is provided by the image data number reducing circuit 31 of the image encoding apparatus of FIG. This is a circuit for restoring the thinned image data by interpolation and restoring the progressive scan image data of the same image data number and the same data rate as the input image data HVi.
A progressive scan conversion process is performed.

The image data number restoring circuit 50, like the image data number restoring circuit 33 shown in FIG. 3, includes a frame memory, detects a motion vector between the previous frame and the frame, and performs interpolation processing. As means, there are provided first interpolation means using only the data of the frame concerned, and second interpolation means using data of the previous frame in the frame memory. Then, the image data number restoration circuit 3
In 3, the first interpolation means and the second interpolation means are adaptively switched in accordance with the detected motion vector.

That is, in the image portion where the motion between the previous frame and the frame is not detected or is very small and the still image portion is detected, the second interpolation means is selected and the image subjected to the thinning process is selected. The interpolation is executed by using the data of the previous frame stored in the frame memory as it is as the data.

In a portion where the movement between the previous frame and the frame is detected to be relatively large, the first
The interpolation means is selected, and the data of the thinned line is generated as the average value of the image data of the lines above and below the frame, for example, as the interpolation data.

Thus, the input image data HVi that has been encoded and transmitted from the image data number restoring circuit 50 is
Is obtained.
The restored progressively scanned image data SVi is supplied to the adding circuit 54.

On the other hand, the encoded and transmitted difference data DFO is variable-length decoded by a variable-length decoding circuit 52 via a buffer memory 51 and supplied to an inverse quantization circuit 53. Then, the difference data dequantized and decoded by the inverse quantization circuit 53 is supplied to the addition circuit 54, and the difference between the original input image data HVi and the restored progressively scanned image data SVo is corrected. Decoded progressively scanned image data DVo substantially equal to the original input image data HVi
Is obtained from the adding circuit 54.

[Second Embodiment] In the first embodiment described above, the difference data DF is the input image data HVi
And the difference between all the pixel data and the restored progressively scanned image data RVi are obtained and transmitted as encoded data DFO. For this reason, when the coding deterioration in the coding unit 1 is of a degree that cannot be ignored, the difference data DF includes the coding error in the coding unit 1 and the decoding data in FIG. The image data decoded by the apparatus reflects the fact, and the coding deterioration is also corrected, so that the image quality is kept high.

By the way, if the coding deterioration in the coding unit 1 is negligible, there is no need to consider the coding error, and therefore, the difference between the image data transmitted by the coding unit 1 The data does not need to be transmitted. In this case, the difference data DF is
Only the difference between the pixel data generated by the interpolation (in the above example, the pixel data in line units since the line is thinned out) and the corresponding pixel data of the input image data HVi may be used.

The second embodiment is an example of a case suitable for a case where coding degradation can be ignored.

FIG. 6 is a block diagram of an image encoding apparatus according to the second embodiment. In the image encoding apparatus shown in FIG. 6, the same parts as those in the image encoding apparatus shown in FIG. Are given the same reference numerals.

In the case of the second embodiment, the input image data HVi of the progressive scanning method (see FIG. 7A) is supplied to the image data number reduction distribution circuit 40. Like the image data number reduction circuit 31 of the first embodiment, the image data number reduction distribution circuit 40 reduces the number of image data of the input image data HVi by performing a thinning process to reduce the number of image data, and only reduces the transmission rate. Instead, the thinned image data is supplied to the delay circuit 35.

That is, in the case of this example, the image data number reduction distribution circuit 40 thins out the odd lines in the odd frames and the even lines in the even frames of the image data HVi of the input sequential scanning system. The image data of the progressive scanning method at a frame rate of 60 Hz is converted into the image data IV of the interlaced scanning method at a frame rate of 30 Hz.
i (see FIG. 7B) and supplies it to the encoding unit 1. This sequential-to-interlaced scan conversion operation is exactly the same as that of the image data number reduction circuit 31 of the first embodiment.

In the image data number reduction distribution circuit 40 according to the second embodiment, odd-numbered frames are composed of odd-numbered lines, and even-numbered frames are composed of even-numbered lines of image data, ie, skipped lines composed of thinned lines. The scanning type image data AIVi (see FIG. 8) is supplied to the subtraction circuit 34 through the delay circuit 35.

As described above, in the second embodiment, as in the first embodiment, the input image data HVi of the progressive scanning type as shown in FIG. The odd lines in the odd frames and the even lines in the even frames are decimated, and the skip scanning conversion is sequentially performed. As shown in FIG. 7B, image data IVi equivalent to the image data of the jump scanning method. , And compression-coded by the coding unit 1. Then, the compressed and encoded data HVo is output as transmission data through the variable length encoding circuit 2 and the buffer memory 3.

In the case of the second embodiment, an interpolation image data generation circuit 41 is provided downstream of the post-processing circuit 32 in place of the image data number restoration circuit 33 of the first embodiment. Provided. The interpolated image data generation circuit 41 converts the interpolated image data CVi (see FIG. 8) corresponding to the image data AIVi (see FIG. 8) which is thinned out by the image data number distribution circuit 40 and supplied to the delay circuit 35,
It is generated from the locally decoded data from the post-processing circuit 32 by interpolation.

The interpolated image data generating circuit 41 also has a frame memory for the interpolating process, similar to the image data number restoring circuit 33 of the above-described first embodiment. A first interpolator using only the data of the frame as the interpolating means, and a second interpolator using the data of the previous frame stored in the frame memory.
Is provided. In the interpolated image data generating circuit 41, like the image data number restoring circuit 33 of the first embodiment, the first and second interpolating means and the second interpolating means are used in accordance with the detected motion vector. Are adaptively switched.

As described above, in this embodiment, every other horizontal line is thinned out. Therefore, this interpolated image data generation circuit 41 constitutes a horizontal line interpolation circuit. Interpolated image data CVi
Is the interlaced image data for the thinned image data portion. This interpolated image data CVi
7 is composed of the image data of the line marked with ◇ in FIG. 7C.

Accordingly, the subtraction circuit 34 obtains difference data IDF (see FIG. 8) between the input image data HVi and the interpolated image data CVi for the thinned image portion. Then, this is quantized by the quantization circuit 36,
The data is variable-length coded by the variable-length coding unit 37 and output as output difference data IDFo through the buffer memory 37.

A decoding device corresponding to the encoding device of the second embodiment may have exactly the same configuration as the decoding device of FIG. 5 described as corresponding to the first embodiment. it can. The difference between the decoding of the first embodiment and the decoding of the second embodiment is that the data obtained from the inverse quantization circuit 53 for the difference data Dfo is only the interpolation image data in the second embodiment. Is that

Also in the case of the second embodiment, as in the first embodiment, it is possible to realize image coding that maintains high image quality while minimizing coding deterioration.

In addition, in the case of the second embodiment, the difference data IDF is a difference with respect to the image data of the horizontal line subjected to the thinning process. The size of the data will be smaller.

Since the interpolation processing is adaptively switched in the interpolation image data generation circuit 41, the data amount of the difference data IDF is minimized, and the increase in the transmission data amount can be expected to be minimized.

In the above description, the difference data IDF
Is quantized as it is, but the difference data may of course be compressed and encoded using DCT processing or the like.

In the above description, the interpolated image data generating circuit 41 uses a motion vector detecting circuit for adaptively switching between the first interpolating means and the second interpolating means. Was explained to be provided in the
Since the delay circuit 35 also includes a frame memory, the delay circuit 35 may be provided with a motion vector detection circuit, and the detection output may be supplied to the interpolation adaptive switching circuit of the interpolation image data generation circuit 41.

The image decoding apparatus according to the second embodiment can be configured in exactly the same manner as the image decoding apparatus shown in FIG.

[Modification] In the first and second embodiments described above, differences are obtained for all the pixel data of the input image data HVi, and the difference data is encoded and transmitted. Difference data may not be output for blocks or macroblocks for which motion has not been detected by the detection signal. This is because there is almost no deterioration in a still image portion in which no motion is detected, even if interpolation is performed by an interpolation process using data of a previous frame in a decoding device.

In the first and second embodiments described above,
Although the image data is thinned by half for each horizontal line of image data, the present invention is also applicable to a case where image data is thinned for each pixel.

Although the description has been given of the case where the input image data is of the progressive scanning system and the frame rate is 60 Hz, it is needless to say that the present invention can be applied to the case where the frame rate is 59.94 Hz or 50 Hz. Nor. In this case, the frame rate of the image data is 30 Hz, 29.75 Hz, or 25H in terms of the image data of the interlace scanning frame rate.
Even in the case of z, the image encoding method according to the present invention is applicable.

The encoding section 1 is not limited to the MPEG compression encoding system, and it goes without saying that various other image encoding systems can be used.

[0106]

As described above, according to the present invention, even when the data rate of image data is high and the amount of data is large, encoding deterioration is minimized and high image quality is maintained. Image coding can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of an image encoding device according to the present invention.

FIG. 2 is a diagram for explaining a processing operation of a main part of the first embodiment.

FIG. 3 is a block diagram of a specific configuration example of a partial circuit according to the first embodiment;

FIG. 4 is a diagram for explaining a processing operation of a main part of the first embodiment.

FIG. 5 is a block diagram of an embodiment of an image decoding device corresponding to the image encoding device of the first embodiment.

FIG. 6 is a block diagram of a second embodiment of the image encoding device according to the present invention.

FIG. 7 is a diagram for describing a processing operation of a main part of the second embodiment.

FIG. 8 is a diagram illustrating a processing operation of a main part of the first embodiment.

FIG. 9 is a block diagram illustrating an example of a compressed image encoding unit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Encoding part, 2 ... Variable length encoding circuit, 3 ... Buffer circuit, 4 ... Rate control circuit, 5 ... Rate control circuit, 11 ...
Preprocessing circuit, 12... Subtraction circuit (prediction error calculation circuit), 1
3 DCT processing circuit, 14 quantization circuit, 15 inverse quantization circuit, 16 inverse DCT processing circuit, 17 local addition circuit for decoding, 18 frame memory, 19 motion compensation circuit,
20: motion vector detection circuit, 31: image data number reduction circuit, 32: post-processing circuit, 33: image restoration circuit,
34: difference operation circuit, 35: delay circuit, 36: quantization circuit, 37: variable length encoding circuit, 38: buffer circuit, 4
0: image data number reduction distribution circuit, 42: interpolation image data generation circuit, 331: synthesis circuit, 332: average value interpolation data generation circuit, 333: previous frame data transmission circuit, 33
4 ... motion vector detection circuit, 335 ... switch circuit, 3
36 ... Interpolation adaptive switching circuit

Continued on the front page F term (reference) 5B057 AA20 BA21 CA08 CA12 CA16 CB08 CB12 CB16 CC01 CG03 CG05 CH01 CH11 CH18 5C059 KK01 LA06 LB05 LB12 LB15 LB16 MA00 MA01 MA05 MA14 MA23 MC11 MD02 ME02 NN01 NN21 PP05 RC06 SS06 TA45 TB01 TB04 TC12 TC20 TD11 UA02 UA05 UA12 UA32 UA33 UA38 5C063 AA11 AB03 AB07 AC01 CA05 CA07 CA09 CA11 5J064 AA01 BA09 BB01 BB04 BB10 BB12 BC01 BC02 BC08 BC16 BC24 BC25

Claims (28)

[Claims] An image encoding apparatus for encoding input image data in units of one screen, comprising: an image data number reducing unit for thinning out the number of data of one screen of the input image data; An image encoding unit that encodes the image data from the image data number reduction unit in units of one screen, a decoding unit that generates decoded image data obtained by decoding the encoded image data, Image data number restoring means for converting the decoded image data from the converting means into the same number of restored image data as the number of the input image data using interpolation processing, and restored image data from the image data number restoring means. A delay unit that delays the input image data to correct a delay error with the input image data; an image data from the image data number restoring unit; Difference calculation means for generating difference data from input image data, difference data coding means for coding the difference data from the difference calculation means in units of one screen, and one screen from the image coding means Output means for outputting, for transmission, encoded image data in units of minutes, and encoded difference data from the difference data encoding means for image data on the same screen as the encoded image data. Image coding device. 2. The image encoding apparatus according to claim 1, wherein said input image data is image data of a progressive scanning method, and said image data number reducing means includes a unit for every other horizontal line of said input image data. An image encoding device that extracts image data corresponding to interlaced scanning image data by extracting the horizontal line positions in adjacent frames while extracting the data. 3. The image coding apparatus according to claim 2, wherein the frame rate of the input image data of the progressive scanning method is 60 Hz, 59.94 Hz or 50 Hz, An image coding device, wherein the frame rate is 30 Hz, 29.97 Hz or 25 Hz. 4. The image encoding apparatus according to claim 1, wherein said image encoding means performs an MPEG compression encoding process, and said decoding means performs said MPEG compression encoding processing. An image coding apparatus for generating image data that has been decompressed and decoded using a local decoded signal used in a motion compensation process in the process. 5. The image encoding apparatus according to claim 4, wherein said image data number restoring means includes a memory for delaying image data by one screen and uses data for a plurality of screens. A first interpolation unit for restoring the number of image data by interpolation; and a second interpolation unit for restoring the number of image data using only image data in the same screen. An image encoding apparatus adapted to adaptively switch between the interpolation means and the second interpolation means. 6. The image encoding apparatus according to claim 5, wherein the difference data is not output for the image data determined to be a still image without a motion being detected by the motion detection signal. An image encoding device characterized by the following. 7. An image encoding apparatus for encoding input image data in units of one screen, comprising: an image data number reduction unit for thinning out the number of data of one screen of the input image data; An image encoding unit that encodes the image data from the image data number reduction unit in units of one screen; and data corresponding to the data thinned out by the image data number reduction unit, the image encoding unit Interpolation image data generation means for generating by interpolation processing from image data obtained by decoding encoded image data, and for correcting a delay error between the interpolation image data from the interpolation image data generation means and the input image data. Delaying means for delaying the input image data; and interpolating image data from the interpolation image data generating means; Difference calculation means for generating difference data between the interpolated image data and the corresponding image data; difference data coding means for coding the difference data from the difference calculation means in units of one screen; Means for outputting, for transmission, encoded image data in units of one screen from the means and encoded difference data from the difference data encoding means for image data on the same screen as the encoded image data. Means for encoding an image. 8. The image encoding apparatus according to claim 7, wherein said input image data is image data of a progressive scanning method, and said image data number reducing means includes a unit for every other horizontal line of said input image data. An image encoding apparatus that extracts image data corresponding to interlaced scanning image data by extracting horizontal data at different positions in adjacent frames. 9. The image encoding apparatus according to claim 7, wherein a frame rate of the input image data of the progressive scanning method is 60 Hz, 59.94 Hz or 50 Hz, An image coding device, wherein the frame rate is 30 Hz, 29.97 Hz or 25 Hz. 10. The image encoding apparatus according to claim 7, wherein said image encoding means performs an MPEG compression encoding process, and said interpolation image data generating means comprises an MPEG compression means. An image encoding apparatus for generating image data that has been decompressed and decoded using a locally decoded signal used in a motion compensation process in an encoding process. 11. The image encoding apparatus according to claim 7, wherein said interpolated image data generating means includes a memory for delaying the image data by one screen and uses data for a plurality of screens. A first interpolation unit that obtains the interpolated image data by interpolation; and a second interpolation unit that obtains the interpolated image data using only image data in the same screen. An image encoding apparatus adapted to adaptively switch between the means and the second interpolation means. 12. The image encoding apparatus according to claim 11, wherein the difference data is not output with respect to the image data determined to be a still image without a motion being detected by the motion detection signal. An image encoding device characterized by the following. 13. An image encoding method for encoding input image data in units of one screen, wherein the number of image data is reduced by thinning out the number of data of one screen of the input image data. An image encoding step of encoding the image data of which the number of data has been reduced in the image data number reducing step in units of one screen, and decoding and interpolating the image data encoded in the image encoding step Image data number restoring step of converting the decoded image data into the same number of image data as the number of data of the input image using processing, and correcting a delay error between the restored image data from the image data number restoring means. The input image data delayed in order to generate a difference between the image data obtained in the image data number restoration step, and a difference calculation step, and the difference data obtained in the difference calculation step A difference data encoding step of encoding in units of one screen; encoded image data in units of one screen obtained in the image encoding step; and the encoded image data obtained in the difference data encoding step. An output step of outputting, for transmission, encoded difference data of image data for one screen of the same screen. 14. The image encoding method according to claim 13, wherein the input image data is image data of a progressive scanning method, and in the image data number reduction step, every other horizontal line of the input image data is provided. An image encoding method which generates image data corresponding to interlaced scanning image data by extracting the horizontal line position in adjacent frames while extracting the data of adjacent frames. 15. The image encoding method according to claim 14, wherein a frame rate of the input image data of the progressive scanning method is 60 Hz, 59.94 Hz or 50 Hz, and an image generated in the image data number reduction step. Data frame rate is 30Hz, 29.97Hz or 25H
z is an image encoding method. 16. The image encoding method according to claim 13, wherein the image encoding step performs an MPEG compression encoding process, and the image data number restoring step includes the image encoding step. An image encoding method characterized by generating image data that has been decompressed and decoded using a locally decoded signal used in a motion compensation process in a decoding step. 17. The image encoding method according to claim 16, wherein, in the image data number restoring step, a first interpolation process for restoring the image data number using data of a plurality of screens is performed on the same screen. And a second interpolation process for restoring the number of image data using only the image data in the image data. 18. The image encoding method according to claim 17, wherein the difference data is not output for the image data determined to be a still image without a motion being detected by the motion detection signal. Characteristic image coding method. 19. An image encoding method for encoding input image data in units of one screen, comprising: an image data number reduction step of thinning out the number of data of one screen of the input image data; An image encoding step of encoding the image data, the number of which has been reduced by the image data number reducing means, in units of one screen, and data corresponding to the data thinned out by the image data number reducing means, An interpolated image data generating step of generating the interpolated image data from the decoded image data by interpolation processing, and the input delayed to correct a delay error between the interpolated image data obtained in the interpolated image data generating step Image data, a difference calculation step of generating difference data between the interpolation image data obtained in the interpolation image data generation step, and the difference calculation step obtained in the difference calculation step Differential data encoding step of encoding minute data in units of one screen; encoded image data in units of one screen obtained in the image encoding step; and the code obtained by the difference data encoding unit. An output step of outputting, for transmission, the encoded image data and the encoded difference data of the image data on the same screen. 20. The image encoding method according to claim 19, wherein the input image data is image data of a progressive scanning method, and in the image data number reduction step, every other horizontal line of the input image data is provided. An image encoding method which generates image data corresponding to interlaced scanning image data by extracting the horizontal line position in adjacent frames while extracting the data of adjacent frames. 21. The image encoding method according to claim 20, wherein a frame rate of the input image data of the progressive scanning method is 60 Hz, 59.94 Hz or 50 Hz, and an image generated in the image data number reduction step. Data frame rate is 30Hz, 29.97Hz or 25H
z is an image encoding method. 22. The image encoding method according to claim 19, wherein the image encoding step performs an MPEG compression encoding process, and the interpolation image data generating step includes the MPEG compression An image encoding method for generating image data that has been decompressed and decoded using a locally decoded signal used in a motion compensation process in an encoding process. 23. The image encoding method according to claim 22, wherein, in said interpolated image data generating step, a first interpolation process for obtaining said interpolated image data using data of a plurality of screens is performed within the same screen. And a second interpolation process for obtaining the interpolated image data using only the image data of (c) is adaptively switched in accordance with the motion detection signal. 24. The image encoding method according to claim 22, wherein the difference data is not output for the image data determined to be a still image without a motion being detected by the motion detection signal. Characteristic image coding method. 25. An image data decoding means for decoding coded image data transmitted after being encoded with a reduced number of image data, and an image of the image data decoded by said image data decoding means. Image data number restoring means for restoring the data number to the original image data number; original image data transmitted from the encoding side; and image data number restored image data restored from the encoded image data. Difference data decoding means for decoding the encoded data of the difference data, and addition means for adding the difference data decoded by the difference data decoding means to the image data decoded by the decoding means. Wherein the decoded image data of the original image data is obtained from the adding means. 26. The image data decoding means for obtaining interlaced scanning image data, and the adding means for obtaining progressive scanning image data. The image decoding device according to claim 25. 27. An image data decoding means for decoding encoded image data which has been transmitted after being encoded with the number of image data reduced by a thinning process, and an image decoded by said image data decoding means. Image data number restoring means for restoring the image data number of the data to the original image data number; thinned image data of the original image data transmitted from the encoding side; and the encoded image Difference data decoding means for decoding encoded data of difference data from the interpolated image data corresponding to the thinned image data restored from the data, and difference data decoded by the difference data decoding means And an adding means for adding the image data decoded by the decoding means, and obtaining decoded image data of the original image data from the adding means. Image decoding apparatus. 28. The image data decoding means for obtaining interlaced scanning image data, and the adding means for obtaining progressive scanning image data. An image decoding apparatus according to claim 27.