JPH09294262A - Image coding device - Google Patents

Abstract

(57) [Summary] [Object] To improve image quality when image data is divided into drawings and the data of each divided screen is processed in parallel, and control is simplified. SOLUTION: An input screen is divided into a plurality of areas, partial encoders for encoding the respective areas are operated in parallel, and encoding information near the boundary of the areas encoded by a certain partial encoder is adjacent to each other. Transfer to another partial encoder. The partial encoder that has received the encoded information, when encoding near the boundary,
Since the coding conditions of adjacent areas can be referred to, discontinuous coding can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image coding device,
In particular, it relates to an apparatus for encoding a digitally compressed image by parallel processing.

[0002]

2. Description of the Related Art When digitally expressing image data for transmission or storage, encoding is performed to compress the amount of data to be transmitted or stored. As such an encoding method, there is a method of reducing redundancy by utilizing temporal or spatial correlation of image information (image data).

On the other hand, as a method of reducing the redundancy by utilizing the temporal correlation, there is a method of encoding a difference between two screens (frames) or detecting a motion of an image to perform motion compensation. . Further, as a method of reducing redundancy by utilizing spatial correlation, an image is divided into blocks of a predetermined size (for example, 8 pixels in each of the vertical direction and the horizontal direction), and data in the blocks is orthogonally transformed. However, there is a method in which the conversion coefficient is scan-converted (for example, rearranged in order from a low frequency component to a high frequency component) and variable length coding is performed.
The ITU-T standardized image coding methods H.261 and H.263, and the MPEG (Moving Picture Experts Group) standardized image coding method (hereinafter abbreviated as MPEG) are the above two methods. Are used together. This MPEG is MPEG
There are two, 1 and MPEG2, and the recommendation of MPEG1 is ISO / IEC11172-
2, MPEG2 recommendation is described in ISO / IEC13818-2. The present invention can be applied to any of these.

FIG. 15 shows an example of the structure of an image coding apparatus for generating coded data by such a general method.

In FIG. 15, reference numeral 151 is a reorder control unit for changing the coding frame order, 152 is a subtracter for calculating the difference between the coding frame and the reference frame,
53 is a DCT unit that performs discrete cosine conversion
Reference numeral 154 is a quantizer, 155 is a scan converter, 156 is a variable length coding unit, and 157 is a buffer control unit for controlling a bitstream output buffer. Further, 158 is an inverse quantizer, 159 is an inverse DCT unit that performs inverse discrete cosine transform, 1510 is an adder that generates a reproduced image, 1511 and 1512 are forward prediction frame memory and backward prediction frame that store reference images, respectively. Memory, 1
Reference numeral 513 is a motion compensator that performs motion compensation between the coded frame and the reference image, and 1514 is a motion vector detector that detects the motion of the coded frame with respect to the reference image. 158,
Reference numerals 159, 1510, 1511, and 1512 have a decoding function and are provided in the encoder to ensure the consistency between the encoder and the decoder, and are called local decoders. A control unit 1515 controls a code amount assigned to a frame to be encoded and controls a quantization step.

Next, the operation of the general image coding apparatus shown in FIG. 15 will be described. This apparatus can be applied to various image encoding apparatuses such as MPEG, but an example of encoding an HDTV image defined as a high level of MPEG2 will be described.

One frame of an HDTV image consists of horizontal 1920 pixels and vertical 1080 lines as shown in FIG. This sideways,
It is divided vertically into 16 pixels each. A unit of one division is called a macroblock (hereinafter abbreviated as MB). One frame is divided into a horizontal 120 MB, a vertical 68 MB, and a total of 8160 MB.

On the other hand, HDTV images are
It is encoded with reference to the preceding and following frames. Forward prediction when predicting the current frame from past frames,
The case of predicting the present frame from the future frame is called backward prediction, and the case of predicting the present frame from both past and future frames is called bidirectional prediction. An intra frame (I frame) is a frame that is encoded without interframe prediction, a forward prediction frame (P frame) is a frame that is encoded by forward prediction, and a bidirectional prediction is a frame that is encoded by bidirectional prediction. It is called a frame (B frame). The prediction method in the P frame and the B frame is determined for each macro block.

That is, the macroblock in the P frame becomes an intra macroblock without motion compensation or a forward prediction macroblock, and the macroblock in the B frame becomes an intra macroblock, a forward prediction macroblock, or a backward prediction macroblock. It will be one of the bi-predictive macroblocks.

Now, input frames in the order of P frame P0, B frame B2, B frame B3, I frame I1, B frame B5, B frame B6, P frame P4, B frame B8, B frame B9, P frame P7. An example of encoding is shown in FIG. The arrow shown in the figure indicates the direction of prediction. In order to encode a B-frame, the reference frames on both sides must first be encoded. Therefore, the encoding order is P0, I1, B2, B3, P4, B5, B6, P7, B8, B9. The operation of rearranging the input images in the order of encoding is called reordering. The reorder control unit 151 in FIG. 15 executes this operation. Further, the reorder control unit 151 also performs processing such as preprocessing filters and downsampling of color signals. The prediction method is determined for each macroblock as described above.

A macroblock in the P frame P4 is assigned to I
FIG. 18 shows an example of encoding with reference to the frame I1. The portion of P4 that most resembles a macroblock is searched from the I frame I1 and the error from that portion is encoded. At the same time, the moving amount is encoded as a motion vector. The process of searching for the most similar part is called motion vector detection, and is executed by the motion vector detector 1514 of FIG. As a motion vector detecting method, a method of detecting a minimum error portion for each pixel is well known. The operation of finally extracting the most similar portion and encoding it is called motion compensation, and is executed by the motion compensator 1513 in FIG. Furthermore, the error between the most similar part to the macroblock to be encoded is
It is calculated by the subtractor 152 in FIG. The DCT unit 153 performs orthogonal transformation in units of vertical 8 pixels and horizontal 8 pixels to generate coefficients of spatial frequency components. Further, the DCT coefficient is quantized by the quantizer 154. This operation
The information is compressed by dividing the DCT coefficient by a predetermined coefficient to reduce the precision of expressing the DCT coefficient.

Next, the scan conversion 155 rearranges the DCT coefficients in order from low frequency to high frequency, and the variable length encoder 156 performs variable length coding. Further, the additional information such as the motion vector described above is also variable-length coded by the variable-length encoder 156. The buffer controller 157 accumulates the bit stream thus obtained in the output buffer and flattens the output bit amount. At the same time, the output buffer is monitored to detect the generated code amount, and when the generated code amount is too large, the quantization accuracy is coarsened to suppress the generated code amount. Such control is performed by the control unit 1515. The inverse quantizer 158 multiplies the DCT coefficient by a predetermined coefficient, which is the inverse of quantization. Inverse DCT159
Then, the error of the actual image is reproduced from the coefficient of the spatial frequency component by the calculation opposite to that of DCT. The added error and the pixel after motion compensation are added by the adder 1510 to reproduce the encoded macroblock. This playback data, when used to encode the subsequent frame,
It is stored in the frame memory 1511 or 1512.

A huge amount of processing is required to encode a large image such as an HDTV image, and a method of distributing the processing is known to execute this in real time. There is a screen division method as a processing distribution method. For this, see, for example, the 1994 Annual Conference of the Television Society of Japan, pp. 171 "Characteristics of split screen HDTV encoding system".
Or, it is described in "Examination of HDTV screen division coding method" on page 173 of the same lecture collection. An example of screen division is shown in FIG. In this example, the HDTV image is divided into eight areas each including 34 macroblocks in the vertical direction and 30 macroblocks in the horizontal direction, and each screen is encoded in parallel. In the case of the NTSC system, a normal TV image has 30 macroblocks vertically and 44 to 45 macroblocks horizontally, and therefore includes more macroblocks than one screen divided as shown in FIG. Therefore, it is possible to encode an HDTV image by operating in parallel eight image encoders having the same processing capability as the NTSC image encoder.

[0014]

On the other hand, as described above, the HDTV
The present inventors have studied a coding method in which a large screen such as an image is divided into eight screens, and each divided screen is independently processed in parallel by eight encoders under independent coding conditions. However, in this independent and parallel processing method, since the coding conditions at the boundary part of the divided screen are independent, the image quality is degraded at the boundary part, and the boundary line is visible in an extreme case. This problem has been clarified by the present inventors.

In order to avoid this problem, the present inventors have also proposed a method in which the motion compensation area, which is one of the coding conditions, is overlapped on both sides of the boundary of the divided screen to enable motion compensation beyond the boundary. Was reviewed by. However, in this case, not only the frame memory for the overlap is added in the local decoder, but also the reference images for the overlap have to be transferred by the two partial encoders, The drawback was that the control became very complicated.

The present invention has been made in view of the above background, and an object of the present invention is to improve the image quality when the image data is divided into drawings and the data of each divided screen is processed in parallel, and control is performed. An object is to provide an image encoding device that can be simplified.

[0017]

A typical embodiment of the present invention for achieving the above object is an image coding apparatus for compressing a data amount of transmission or storage of image data, which is a divided screen from the image data. Separator (SWi
n) and a plurality of split screen data encoders that encode the split screen data separated by the separator (SWin)
(0 to 7) and the plurality of split screen data encoders (0 to 7)
And a synthesizer (SWout) for generating compressed data of the image data by synthesizing the output of 7), and one split screen data of the plurality of split screen data encoders (0 to 7). The encoding information of the one divided screen data encoder is transferred from the encoder (0) to the other divided screen data encoder (1), and the other divided screen data encoder according to the encoding information. The encoding operation of (1) is controlled (see FIGS. 2 and 3).

Therefore, the other split screen data encoder (1) that has received the coding information can refer to the coding conditions of the adjacent areas when coding near the boundary of the split screen.
Discontinuous encoding can be avoided. This allows
It is possible to prevent deterioration of image quality at the boundary.

A specific embodiment of the present invention is characterized in that the plurality of divided screen data encoders operate at different timings when encoding each data of the divided screen existing in the same row of the image data. (See FIGS. 8 and 9).

Thus, a certain split screen data encoder
After (0) encodes the boundary part, another adjacent divided screen data encoder (1) can encode the boundary part, so that the above-mentioned encoded information can be transferred and referred to. Become.

A more specific embodiment of the present invention is characterized in that the coding information includes any one of quantization step information, motion vector information, and intra / inter coding information. The intra / inter coding information is characterized by indicating whether it is intra coding that does not use interframe prediction or inter coding that uses interframe prediction (FIG. 4, FIG. 5, FIG. 6, FIG. (See FIG. 7).

Quantization steps, intra / inter coding information, and motion vectors are important for coding control, and the inclusion of these in coding information to be transferred is highly effective from the viewpoint of improving image quality.

Other objects and features of the present invention will be apparent from the following examples.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION An image coding apparatus according to a first embodiment of the present invention will be described below with reference to FIGS. 1 to 9.

FIG. 3 shows the overall configuration of the image coding apparatus of this embodiment. Further, FIG. 2 is an example of division of an image encoded by the image encoding device. HD in this example
The TV image is divided into eight areas each including 34 macroblocks vertically and 30 macroblocks horizontally. Screen 0 of Figure 2
The eight areas of the screen 7 are the encoders 0 to 8 of the encoder 7 in FIG.
Are coded in parallel by the partial encoders. The image input is performed from the upper left to the lower right for each scanning line. An area to be encoded is set in each partial encoder, and pixel data in the corresponding area is selectively fetched.

The image input section of FIG. 3 as a separator for separating each data of the split screen from the image data has eight switches.
SWin shows this schematically.

Further, partial bitstreams are generated in parallel by the partial encoders 0 to 7 as a plurality of divided screen data encoders for encoding the divided screen data.

Eight switches SWout of the bit stream output section of FIG. 3 schematically shown operate as a synthesizer for producing compressed data of image data by synthesizing outputs of a plurality of divided screen data encoders. . Therefore, the partial bitstreams from the partial encoders 0-7 are switched SWou
It is switched by t and is sent from the upper left to the lower right of the entire screen to generate compressed data of image data.

FIG. 1 shows each structure of the eight partial encoders shown in FIG. In FIG. 1, 11 is a reorder control unit for changing the coding frame order, 12 is a subtractor for calculating the difference between the coding frame and the reference frame,
Reference numeral 13 is a DCT unit, 14 is a quantizer, 15 is a scan converter, 16 is a variable length coding unit, and 17 is a buffer control unit for controlling a bitstream output buffer. Also one
8 is an inverse quantizer, 19 is an inverse DCT unit, 110 is an adder that generates a reproduced image, 111 and 112 are forward prediction frame memories and backward prediction frame memories that store reference images, respectively, and 113 is an encoded frame and reference. A motion compensator that performs motion compensation on the image, and 114 is a motion vector detector that detects the motion of the encoded frame with respect to the reference image. 1
8, 19, 110, 111, 112 have a decoding function,
The local decoder is provided in the encoder to ensure the consistency between the encoder and the decoder. A control unit 115 controls a code amount assigned to a frame to be encoded and controls a quantization step. In addition, 1
Reference numeral 16 is a screen selection unit and 117 is an output switching unit.

Next, the operation of the partial encoder shown in FIG. 1 will be described. The outline of the encoding operation of the divided partial images is as follows. At 116, a predetermined portion is selectively fetched from the split screen as shown in FIG. Reorder control unit 1
In 1, the operation (reorder) of rearranging the input images in the order of encoding is executed. Further, processing such as pre-processing filter and color signal down-sampling is also performed in 11. Encoding is performed for each macroblock. Motion vector detection is performed at 114. The image that most resembles the macroblock to be encoded is the prediction frame memory 111
Alternatively, it is detected from either 112. As a motion vector detecting method, a method of detecting a minimum error portion for each pixel is well known. Also, the motion compensation that finally retrieves the most similar portion is performed at 113. Further, the error between the most similar portion to the macroblock to be encoded is calculated at 12. In the DCT 13, orthogonal transformation is performed in units of vertical 8 pixels and horizontal 8 pixels to generate coefficients of spatial frequency components. Further, the DCT coefficient is quantized by the quantizer 14.

Next, the scan conversion 15 rearranges the DCT coefficients in order from low frequency to high frequency, and the variable length encoder 16 performs variable length coding. Also. The additional information such as the motion vector described above is also variable-length coded by 16. In the buffer control unit 17, the bit stream thus obtained is accumulated in the output buffer and the output bit amount is flattened. At the same time, the output buffer is monitored to detect the generated code amount, and when the generated code amount is too large, the quantization accuracy is coarsened to suppress the generated code amount. Such control is performed by the control unit 115.
The inverse quantizer 18 multiplies the DCT coefficient by a predetermined coefficient, which is the inverse of the quantization. The inverse DCT 19 reproduces the error of the actual image from the coefficient of the spatial frequency component by the calculation opposite to that of the DCT. The error thus obtained and the pixel after motion compensation are added by the adder 110 to reproduce the coded macroblock. This reproduction data is stored in the frame memory 111 or 112 when it is used for encoding a subsequent frame. At 117, bitstream switching control is performed.

Next, the characteristic processing of this embodiment will be described.
In this embodiment, the coded information near the boundary of the partial screen is transferred to the adjacent partial coder, and the adjacent partial coder is controlled according to this coded information. In FIG. 3, the coding information of the right boundary portion of the screen 0 of FIG. 2 is sent from the partial encoder 0 to the partial encoder 1. This information is indicated by a broken line in FIG. Similarly, the encoding information of the right boundary portion of the screen 1 in FIG. 2 is sent from the partial encoder 1 to the partial encoder 2, and the partial encoder 2 encodes the right boundary portion of the screen 2 in FIG. Information
It is sent to the partial encoder 3. The coded information is similarly sent to the partial encoders 4 to 7. The received encoded information is input to the control unit 115, as indicated by the broken line in FIG. When the control unit 115 is composed of a CPU, a local bus of the CPU (a bus connecting each CPU between each partial encoder) can be used as a transfer path of the encoded information.

Next, a method of controlling the coding based on the received coding information will be described. First, if the quantization steps are the same on both sides of the boundary (for example, the quantization step of the leftmost macroblock of the screen 1 is set to the screen 0).
(Equal to the quantization step of the rightmost macroblock of), or with no significant change, the image discontinuity is mitigated. In FIG. 4, the quantization step input on the horizontal axis (for example, the quantization step of the rightmost macroblock of the screen 0) is taken, and the quantization step of the macroblock controlled by this (the leftmost macroblock of the screen 1 (Quantization step) An example of control is shown on the vertical axis. In this example, the quantization step of the macroblock is determined within a range in which a predetermined allowable change amount is added to or subtracted from the input quantization step. The quantization step in the range between the two broken lines in FIG. 4 is controlled as an allowable value.

That is, when the coding information of the quantization step of the partial encoder 0 is transferred to the partial encoder 1, the quantization step of the partial encoder 1 depends on the quantization step of the partial encoder 0. As a result, when the quantization step of the rightmost macroblock of the screen 0 is small, the subcoder 1 is controlled so that the quantization step of the leftmost macroblock of the screen 1 becomes small, so that the screen 0 and the screen 1 are separated from each other. The deterioration of the image quality at the boundary is prevented.

For intra / inter coding information indicating intra coding without interframe prediction or inter coding with interframe prediction, the intra / inter coding determination condition of the macroblock is controlled. .

That is, when the intra / inter coded information that the partial encoder 0 is coded by the intra coding is transferred to the partial encoder 1, the encoding operation of the partial encoder 1 is performed by the intra encoder of the partial encoder 0. It becomes dependent on the encoding operation. As a result, when the rightmost macroblock of screen 0 is encoded by intra-coding, the partial encoder 1 is controlled so that the leftmost macroblock of screen 1 is encoded by intra-coding, Degradation of image quality at the boundary between 0 and screen 1 is prevented.

The method of determining whether the coding is intra-coding or inter-coding is based on the variance VA of the macroblock itself to be coded.
The ROR and the variance VAR of the difference data after motion compensation are used. These are expressed by the following equations. However, OR represents each luminance pixel data of the macro block to be encoded, and S represents each prediction image data after motion compensation. Further, Σ represents the sum total of the luminance data in the macroblock.

VAR = Σ ((OR−S) × (OR−S)) / 256 VAROR = Σ (OR × OR) / 256 − ((ΣOR) / 256) × ((ΣOR) /
256) That is, VAR represents the sum of squared differences between the luminance pixel data at each pixel and the predicted image data after motion compensation.
R represents the difference between the sum of the squares of the image data at each pixel and the square of the sum of the averages of the image data at each pixel, which has nothing to do with motion compensation.

By comparing these magnitudes, intra-coding without using interframe prediction is performed when the correlation of image data of data between frames is small and VAR is larger than VAROR, and conversely, when VAROR is larger than VAR, interframe prediction is performed. Is used for inter coding.

In FIG. 5, a line having a slope of 45 degrees serves as a boundary for determining whether intra coding or inter coding. The vicinity of the origin is inter coded. This example is described in the reference model 8 of the image coding method H.261 and the simulation model 3 of MPEG1.

In the present embodiment, when the coding information indicating whether the sub-coder 0 is intra-coded or inter-coded is transferred to the sub-coder 1, it is determined whether the sub-coder 1 is intra-coded or inter-coded. The encoding control depends on the encoding information of the partial encoder 0. As a result, when the rightmost macroblock of the screen 0 is intra-coded, the partial encoder 1 is controlled so that the leftmost coding of the screen 1 is likely to be intra-coded. It is possible to prevent the image quality from deteriorating at the boundary between the and.

That is, as shown in FIG. 5 or FIG.
If the boundary of the adjacent divided image is an intra code, the macroblock to be encoded is likely to be an intra code, and if the boundary of the adjacent divided image is an inter code, the macroblock to be encoded is likely to be an inter code. Control judgment. In FIG. 5, the inclination of the determination boundary line is changed, and in FIG. 6, a predetermined offset is provided.

On the other hand, in the motion vector detection, the accuracy is higher when the motion vector is determined by referring to the surrounding vectors than when it is determined by a single macroblock. In the present embodiment, the vector of the boundary of the adjacent divided image is referred to, and the vector of the macroblock to be coded is easily selected in the vicinity thereof. As shown in FIG. 7, a vector (indicated by a solid line) for several macroblocks at the boundary between the split screens 1 and 2 is transferred, and a vector (indicated by a broken line) in parallel with the vector (indicated by a rectangle) The vector in (type) is controlled so that it can be easily selected. If it exceeds the boundary, it is not referred to or vector 0 (no motion) is easily selected.

That is, when the coding information for motion vector detection of the partial encoder 1 is transferred to the partial encoder 2, the motion vector detection coding control of the partial encoder 2 is controlled by the partial encoder 1.
It becomes to depend on the encoding information of. As a result, screen 1
The coding information for detecting the motion vector of the rightmost macro block of is referred to for detecting the motion vector of the leftmost macro block of the screen 2, and the accuracy of the motion vector detection is increased.

Next, the operation timing of each partial encoder will be described. In FIG. 2, in order to use the coding conditions such as the quantization step at the right end of the screen 0, intra / inter coding information, and motion vector detection for the coding control at the left end of the screen 1, the macro at the right end of the screen 0 is displayed. The block must be encoded before the leftmost macroblock of screen 1. In the present embodiment, as shown in FIG. 8, the uppermost slice (one macroblock row) of the screen 0 is encoded, and then the uppermost slice of the screen 1 is encoded during the period in which the second slice of the screen 0 is encoded. Therefore, it is necessary to delay the operation timing of the encoder 1 with respect to the operation timing of the encoder 0. Similarly, it is necessary to delay the operation timing of the encoder 2 from the operation timing of the encoder 1 and delay the operation timing of the encoder 3 from the operation timing of the encoder 2. In FIG. 8, the arrow line indicates the encoding of one slice, and the number attached thereto indicates the encoding order. In this way, if the right partial image is encoded with a delay of one slice period from the left partial image, the encoded information is encoded from the encoder 0 to the encoder 1 and from the encoder 1 to the encoder 2. It is possible to transfer the data from the coder 2 to the coder 3.

FIG. 9 is a diagram showing the encoding timing of each of the partial encoders 1-7. A frame synchronization signal indicating the beginning of one screen, slice synchronization indicating the beginning of a slice, and a macroblock synchronization signal indicating the beginning of macroblock processing are also shown. Each split screen consists of 34 slices,
Since each partial encoder operates at a timing shifted for each slice, after the partial encoder 0 or 4 starts the encoding, it is 37 slices before the partial encoder 3 or 7 finishes the encoding. A period (slice synchronization period 1 to 37) is required. The slice periods -1 and 0 are periods during which precoding of the entire frame and precoding of the first slice by the partial encoders 0 and 4 are performed, respectively. Also,
30 macroblocks (macroblock synchronization periods 1 to 30) are coded in each slice period, and 3
Each macroblock period (Macroblock synchronization period-2
˜0 and macroblock synchronization periods 31 to 33) are provided, and the encoded information is transferred during this period. During the encoding timing period of each partial encoder, the encoded information is transferred at the timing shown by the downward arrow line.

Although the first embodiment of the present invention has been described in detail above, it goes without saying that various modifications can be made within the scope of the technical idea of the present invention. Hereinafter, this modified embodiment will be described.

The second embodiment of the present invention will be described below with reference to FIG. FIG. 10 shows the configuration of the image coding apparatus according to this embodiment. The difference from FIG. 3 which is the first embodiment is that the encoded information is bidirectional. For example, in the first embodiment, only the coding information is transferred from the partial encoder 0 to the partial encoder 1, whereas in the present embodiment, the partial encoder 0 and the partial encoder 1 are transmitted. The encoded information is transferred bidirectionally between the two. Specifically, the partial encoder 1 encodes the leftmost macroblock of the screen 1 at the timing when the partial encoder 0 encodes the rightmost macroblock of the screen 0. That is, the partial encoder 1 executes the encoding with a delay of 29 macroblocks from the partial encoder 0. By doing so, under what conditions the partial encoder 1 is going to encode the rightmost macroblock of the screen 0, and the partial encoder 0 determines which of the leftmost macroblocks of the screen 1 is. It becomes possible to know whether the code is about to be encoded under such conditions. In this way, after the motion vector information on both sides of the boundary, the quantization step information, the intra / inter coding information, etc. are compared, the final coding condition can be determined. This makes it possible to greatly improve the image quality of the boundary portion.

The third embodiment of the present invention will be described below with reference to FIG. FIG. 11 is a diagram showing the operation timing of the partial encoder of this embodiment. The difference from the first embodiment shown in FIG. 8 is that the upper half of the screen and the lower half of the screen are half frames (34
MB) It is to shift and operate. By doing so, the coded information of the upper half screen can be transferred to the lower half screen, and by controlling the coding of the boundary part between them, the image quality of the boundary part between the upper half screen and the lower half screen can be improved. Can be improved.

The fourth embodiment of the present invention will be described below with reference to FIG. FIG. 12 is a diagram showing the operation timing of the partial encoder of this embodiment. The difference from the first embodiment shown in FIG. 8 is that the upper half of the screen and the lower half of the screen are shifted by about a half frame for operation. By doing so, the coded information of the upper half screen can be transferred to the lower half screen, and by controlling the coding of the boundary part between them, the image quality of the boundary part between the upper half screen and the lower half screen can be improved. Can be improved.

The fifth embodiment of the present invention will be described below with reference to FIGS. 13 and 14. In the present embodiment, the present invention is applied to the coding of NTSC images. As shown in FIG. 13, an image of 704 horizontal pixels and 480 vertical lines is divided into four. The size of the partial image is 22 macroblocks horizontally and 15 macroblocks vertically. The four areas of screen 0 to screen 3 of FIG. 13 are encoded in parallel by the four partial encoders of encoder 0 to encoder 3 of FIG. The image input is performed from the upper left to the lower right for each scanning line. An area to be encoded is set in each partial encoder, and pixel data in the corresponding area is selectively fetched. FIG.
The four switches SWin in the image input section of are shown schematically. In addition, the bitstreams generated in parallel by the respective partial encoders are sent from the upper left to the lower right of the entire screen for each macroblock while being switched by the four switches Swout of the bitstream output unit in FIG. To be done. The configuration of the four partial encoders in FIG. 14 is basically the same as that in FIG. In this embodiment, the size of the partial image is smaller than that in the first embodiment, and the partial encoders 0 to 3 can be configured by a microprocessor.

[0052]

According to the present invention, there is provided an image coding apparatus capable of dividing image data into drawings and improving the image quality when parallel processing of data of each divided screen and simplifying control. It becomes possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a partial encoder according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of screen division of an encoded image according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram of a parallel encoding device according to a first embodiment of the present invention.

FIG. 4 is a diagram showing a quantization step control of the first embodiment of the present invention.

FIG. 5 is a diagram showing a first example of decision control for intra / inter coding according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a second example of intra / inter coding determination control according to the first embodiment of the present invention.

FIG. 7 is a diagram showing motion vector control according to the first embodiment of the present invention.

[Fig. 8] Fig. 8 is a diagram illustrating an order of encoding divided screens according to the first embodiment of this invention.

FIG. 9 is a diagram illustrating a timing of encoding a split screen and a timing of transferring encoded information according to the first embodiment of this invention.

FIG. 10 is a configuration diagram of a parallel encoding device according to a second embodiment of the present invention.

[Fig. 11] Fig. 11 is a diagram illustrating the order of encoding divided screens according to the third embodiment of this invention.

[Fig. 12] Fig. 12 is a diagram illustrating the order of encoding divided screens according to the fourth embodiment of the present invention.

FIG. 13 is a diagram showing an example of screen division of an encoded image according to a fifth embodiment of the present invention.

FIG. 14 is a configuration diagram of a parallel encoding device according to a fifth embodiment of the present invention.

FIG. 15 is a configuration diagram of a conventional encoding device.

FIG. 16 is a macroblock configuration diagram of an HDTV image.

FIG. 17 is a diagram showing a prediction method of predictive coding.

[Fig. 18] Fig. 18 is a diagram illustrating a motion compensation method for predictive coding.

[Explanation of symbols]

 11, 151: Reorder control unit 12, 152: Subtractor 13, 153: DCT unit 14, 154: Quantizer 15, 155: Scan converter 16, 156: Variable length encoder 17, 157: Buffer control unit 18 158: Inverse quantizer 19, 159: Inverse DCT unit 110, 1510: Adder 111, 1511: Forward prediction frame memory 112, 1512: Backward prediction frame memory 113, 1513: Motion compensation unit 114, 1514: Motion vector detection Units 115 and 1515: Encoding control unit 116: Screen selection unit 117: Bitstream output switching unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichi Tominaga 5-20-1 Kamimizuhoncho, Kodaira-shi, Tokyo Hitachi Ltd. Semiconductor Division (72) Inventor Takayuki Kobayashi 4-36 Yoyogi, Shibuya-ku, Tokyo No. 19 in Graphics Communications Laboratories, Inc. (72) Inventor Norihiko Nagai No. 36-19 Yoyogi, Shibuya-ku, Tokyo Incorporated in Graphics Communications Laboratories (72) Inventor Hideo Arai Tokyo 4 36-19 Yoyogi, Shibuya-ku, Tokyo Inside Graphics Communications Laboratories, Inc.

Claims (3)

[Claims] 1. An image coding apparatus for compressing a data amount of transmission or storage of image data, comprising a separator for separating each data of a divided screen from the image data, and the divided screen separated by the separator. A plurality of split screen data encoders for encoding data, and a synthesizer for producing compressed data of the image data by synthesizing outputs of the plurality of split screen data encoders, Transfer the encoding information of the one divided screen data encoder from one divided screen data encoder of the plurality of divided screen data encoders to another divided screen data encoder, and according to the encoding information An image coding apparatus, wherein the coding operation of the other split screen data encoder is controlled. 2. The plurality of divided screen data encoders operate at different timings when encoding each data of the divided screens existing in the same row of the image data. Image coding device. 3. The coding information includes quantization step information, motion vector information, and intra / inter coding information indicating intra coding without interframe prediction or inter coding with interframe prediction. The image coding apparatus according to claim 1, further comprising at least one of the following.