CA1227867A - Image transmission - Google Patents
Image transmissionInfo
- Publication number
- CA1227867A CA1227867A CA000438840A CA438840A CA1227867A CA 1227867 A CA1227867 A CA 1227867A CA 000438840 A CA000438840 A CA 000438840A CA 438840 A CA438840 A CA 438840A CA 1227867 A CA1227867 A CA 1227867A
- Authority
- CA
- Canada
- Prior art keywords
- blocks
- image
- block
- mean
- coefficients
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/85—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression
- H04N19/86—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression involving reduction of coding artifacts, e.g. of blockiness
Abstract
ABSTRACT
IMAGE PROCESSING
A method of transmission or storage of a television picture involves dividing it into a plurality of blocks, subjecting them individually to a two-dimensional unitary transformation, transmitting or storing the transform coefficients and reconstructing the original blocks by the use of the inverse transformation. To reduce the data rate, the zero sequency coefficient is omitted for most or all the blocks, and the mean levels of the reconstructed blocks are adjusted to reduce visible brightness changes between them. me adjustment may be made to reduce the mean square differences between the elements in two blocks along the common boundary. The division into blocks may give common elements in two blocks along each inter-block boundary. If a picture transition coincides with a block division an indication of this may be sent so that differences between elements along the division are ignored.
IMAGE PROCESSING
A method of transmission or storage of a television picture involves dividing it into a plurality of blocks, subjecting them individually to a two-dimensional unitary transformation, transmitting or storing the transform coefficients and reconstructing the original blocks by the use of the inverse transformation. To reduce the data rate, the zero sequency coefficient is omitted for most or all the blocks, and the mean levels of the reconstructed blocks are adjusted to reduce visible brightness changes between them. me adjustment may be made to reduce the mean square differences between the elements in two blocks along the common boundary. The division into blocks may give common elements in two blocks along each inter-block boundary. If a picture transition coincides with a block division an indication of this may be sent so that differences between elements along the division are ignored.
Description
IMAGE PROCESSING
.
This invention relates to the transmission of images in digital form. The invention may be used to reduce the amount of data which is required to be transmitted to convey an image at a given resolution.
It is known to produce a video signal representing an image by scanning it to produce a signal similar to that used for television, and it is also known to sample the video signal and to convert the samples into digital form so that each picture element (PEW) corresponding to a sample of the video signal is represented by a plurality of binary digits representing the brightness of the particular element or the intensity of a particular color component of that element. Such a method of transmission might be made more efficient by the use of non-linear quantisation of the samples so that a better reproduction of the image is obtained for a given number of bits in the digital coding of each sample than would be obtained if a uniform coding were employed.
As an image contains a large amount of data, it is desirable to reduce as far as possible the amount of data needed to transmit an image. Straightforward digital transmission of an image as described above suffers from the disadvantages that a reduction of the amount of data representing the image will detract markedly from the quality of the reproduced image. In order to overcome this difficulty it has been proposed to convert the digital video signal into a transformed signal in which the coded samples are subjected to a two-dimensional unitary transformation, and then reduce the transformed data. At the receiver the transformed signal is subjected to the inverse transform to regenerate the original image. When transmitted in this way, the data reduction 27~67 does not result in degradation of the image which is as objectionable subjectively as the same data reduction on the image data itself would be.
According to the present invention there is provided a method of transmitting or storing an image including producing an array of samples representing the picture elements of an array of such elements representing an original image, nationally dividing the array of picture elements into a plurality of blocks, for each block subjecting the array of samples to a two-dimensional transformation, transmitting or storing representations of at least some of the coefficients, subjecting the received coefficients in each transformed block to the inverse of the original two-dim2nsional transformation to produce a block of restored samples and reproducing an image from the adjusted blocks, characterized in that for each of at least some of the blocks representations of the zero sequence coefficient are not transmitted or, as the case may be, stored, and values for the mean levels of the restored blocks are calculated so as to substantially minimize visible brightness and/or in a color system, color changes between the particular bloc and at least one of the nearing blocks.
Normally, a unitary transformation, such as the Hadamard or Discrete Cosine transfonn would be used. me adjustment of the Jean levels of the restored blocks may be carried out so as to minimize the mean square value of the brightness differences between the nearest adjacent elements in different blocks at the bowlers between the blocks. This manner of adjustment is satisfactory if no edges in the image coincide with block boundaries, but it can give erroneous results if there is a substantial brightness change in the image lying on a transition between blocks. This difficulty can be overcome by 36~
measuring the mean square brightness difference at each edge between blocks of the original image before transformation and sending an indication if the difference exceeds a threshold value so that the adjustment of the moan levels for adjacent blocks can be arranged to ignore brightness differences at such edges.
To take a practical example, suppose that the original image has 256 x 256 elements and each block is of 8 x 8 elements. It follows that for the whole image there o are 1024 blocks. m e calculations required to minimize the mean square difference for the whole image at once are too lengthy for execution in a reasonable period of time, and therefore it is proposed that the mean level of one block, e.g. that in the top left-hand corner, is set to an arbitrary value, but one that is likely to be reasonable, and those of the other blocks are taken one at a time in sequence are calculated so as to minimize the mean square differences at the one or two edges which each block shares with blocks whose mean level has already been calculated, they may all be subjected to an additive correction by the same amount to bring the average grew level of the entire reproduced image within a desired range.
Instead of calculating the mean level of each block separately, as described above, the Jean levels of a row (or column) of blocks may be calculated in that way and then the blocks dealt with a row ion column) at a time.
Yet another way would be to amalgamate the blacks into groups of four arranged in a square, adjusting the relative mean levels to minimize the mean square differences along the four edges shared by the blocks of the group, then to amalgamate those groups into larger groups (of four groups) using the same technique, and so on until all of the blocks are amalgamated together. As ~22~36~
before an overall additive correction may be made to adjust the grew level of the entire image.
The invention permits a reduction in the amount of data needed to be transmitted (or stored) by omitting from S the data transmitted the do coefficient of all or many of the blocks. Since this coefficient is the one normally transmitted with the greatest accuracy its omission will result in a greater reduction in the data to be transmitted than would be the omission of any other coefficient. If the do coefficient determining the mean level of one block is transmitted, this block could be used as a reference -to which the mean levels of all of the remaining blocks are related directly or indirectly; if the image is such that substantial errors could arise in the mean levels of the other blocks it may be desirable to transmit the do coefficients determining the mean levels of more than one block, e.g. a row or column, or possibly of a few blacks distributed throughout the image area, limiting the extent to which the effect of transmission errors can "propagate" through the image during the reconstruction process.
When the relative adjustment of the mean levels has been effected on the basis of an arbitrarily chosen value in one block selected as reference, the mean levels of all of the blocks may be subjected to a common additive correction kiwi produce a moan grew level within a given range for the entire image.
If the do coefficient of a single block is transmitted or stored to provide, when decoded, a reference for the whole image as described above it may still be desirable to adjust the mean levels to give a mean grew level within a given range for the image, although, in theory at least, such adjustment ought not to be necessary.
:9~278~7 Some embodiments of the invention will now be described with reference to the accompanying drawings, in which:
FIGURE 1 illustrates the division of an image into blocks;
FIGURE 2 shows an example of the numbers of bits allocated to each coefficient of a transformed 8 x 8 block;
FIGURE 3 is a block diagram of one example of an image transmission system using a method according to the lo invention; and FIGURE 4 is a diagram to be used to help to describe a method according to the invention.
In Figure 1, an image is shown as being divided into 64 blocks, each composed of 64 picture elements (pots). It is assumed that the number of pots in both horizontal and vertical directions is the same. As a practical example, it is likely that an image of, say, 256 x 256 Pews might be divided into 1024 8 x 8 blocs.
The image is converted into a video signal, and sampled. Each 8 x 8 array of samples corresponding to a block is subjected to a two-dimensional unitary transformation.
It is impractical to transform the entire image in a reasonable time because the calculation involved in producing the transforms of images having over 65,000 Pews are at present too lengthy even for the fastest computing techniques. Division of the image into smaller blocks, for example, consisting of 8 x 8 Pews means that the computations involved are simplified by a factor of 1,000 and can be executed in a reasonable time by present computing techniques and hardware. Suitable transforms are the Discrete Cosine Transform or the Hadamard transform, for example. The transformation produces an 8 x 8 array of coefficients (in general, an em sample array lZ27Y~6~
produces an NxM array of coefficients, although it is common to discard - or not calculate - the higher sequence coefficients). The sequence in a given direction is the number of sign changes in the corresponding row or column 5 of the basis matrix of the transform used.
Figure 2 shows the number of bits which, in a conventional system, would typically be allocated to coefficients of a transformed block of the image for transmission of that image in the transformed state, ordered as to sequence; thus the top left term indicates that 8 bits are allocated to the zero sequence term, whilst the right hand column and bottom row correspond to the highest sequence coefficient in the two directions.
Considering the block X shown in Figure 1, this block is surrounded by eight blocks A, B, C, D, E, F, G
and H, and the invention makes use of the fact that the lines of Pews of the block X adjacent its four edges will be similar in most cases to the lines of Pews of the blocs B, D, E and G adjacent the same edges. mix wit not be true if a discontinuity in the image separating areas of differing brightness lies along one of the boundary edges of the block X and a method of taking this into consideration is described below.
From a consideration of Figure 2, it will be clear that the zero-sequency, or do coefficient at the top left-hand corner, which represents the average brightness level of the whole block, is normally conveyed by ore bits than the other coefficients. However, if the do coefficient is discarded the amount of data needed to ye transmitted to convey the transformed block is reduced by one-eighth, or possibly more depending on the block size, bit allocation and transformation used. The varying detail of the part of the image within a block is conveyed by the other coefficients so that the discarding of the
.
This invention relates to the transmission of images in digital form. The invention may be used to reduce the amount of data which is required to be transmitted to convey an image at a given resolution.
It is known to produce a video signal representing an image by scanning it to produce a signal similar to that used for television, and it is also known to sample the video signal and to convert the samples into digital form so that each picture element (PEW) corresponding to a sample of the video signal is represented by a plurality of binary digits representing the brightness of the particular element or the intensity of a particular color component of that element. Such a method of transmission might be made more efficient by the use of non-linear quantisation of the samples so that a better reproduction of the image is obtained for a given number of bits in the digital coding of each sample than would be obtained if a uniform coding were employed.
As an image contains a large amount of data, it is desirable to reduce as far as possible the amount of data needed to transmit an image. Straightforward digital transmission of an image as described above suffers from the disadvantages that a reduction of the amount of data representing the image will detract markedly from the quality of the reproduced image. In order to overcome this difficulty it has been proposed to convert the digital video signal into a transformed signal in which the coded samples are subjected to a two-dimensional unitary transformation, and then reduce the transformed data. At the receiver the transformed signal is subjected to the inverse transform to regenerate the original image. When transmitted in this way, the data reduction 27~67 does not result in degradation of the image which is as objectionable subjectively as the same data reduction on the image data itself would be.
According to the present invention there is provided a method of transmitting or storing an image including producing an array of samples representing the picture elements of an array of such elements representing an original image, nationally dividing the array of picture elements into a plurality of blocks, for each block subjecting the array of samples to a two-dimensional transformation, transmitting or storing representations of at least some of the coefficients, subjecting the received coefficients in each transformed block to the inverse of the original two-dim2nsional transformation to produce a block of restored samples and reproducing an image from the adjusted blocks, characterized in that for each of at least some of the blocks representations of the zero sequence coefficient are not transmitted or, as the case may be, stored, and values for the mean levels of the restored blocks are calculated so as to substantially minimize visible brightness and/or in a color system, color changes between the particular bloc and at least one of the nearing blocks.
Normally, a unitary transformation, such as the Hadamard or Discrete Cosine transfonn would be used. me adjustment of the Jean levels of the restored blocks may be carried out so as to minimize the mean square value of the brightness differences between the nearest adjacent elements in different blocks at the bowlers between the blocks. This manner of adjustment is satisfactory if no edges in the image coincide with block boundaries, but it can give erroneous results if there is a substantial brightness change in the image lying on a transition between blocks. This difficulty can be overcome by 36~
measuring the mean square brightness difference at each edge between blocks of the original image before transformation and sending an indication if the difference exceeds a threshold value so that the adjustment of the moan levels for adjacent blocks can be arranged to ignore brightness differences at such edges.
To take a practical example, suppose that the original image has 256 x 256 elements and each block is of 8 x 8 elements. It follows that for the whole image there o are 1024 blocks. m e calculations required to minimize the mean square difference for the whole image at once are too lengthy for execution in a reasonable period of time, and therefore it is proposed that the mean level of one block, e.g. that in the top left-hand corner, is set to an arbitrary value, but one that is likely to be reasonable, and those of the other blocks are taken one at a time in sequence are calculated so as to minimize the mean square differences at the one or two edges which each block shares with blocks whose mean level has already been calculated, they may all be subjected to an additive correction by the same amount to bring the average grew level of the entire reproduced image within a desired range.
Instead of calculating the mean level of each block separately, as described above, the Jean levels of a row (or column) of blocks may be calculated in that way and then the blocks dealt with a row ion column) at a time.
Yet another way would be to amalgamate the blacks into groups of four arranged in a square, adjusting the relative mean levels to minimize the mean square differences along the four edges shared by the blocks of the group, then to amalgamate those groups into larger groups (of four groups) using the same technique, and so on until all of the blocks are amalgamated together. As ~22~36~
before an overall additive correction may be made to adjust the grew level of the entire image.
The invention permits a reduction in the amount of data needed to be transmitted (or stored) by omitting from S the data transmitted the do coefficient of all or many of the blocks. Since this coefficient is the one normally transmitted with the greatest accuracy its omission will result in a greater reduction in the data to be transmitted than would be the omission of any other coefficient. If the do coefficient determining the mean level of one block is transmitted, this block could be used as a reference -to which the mean levels of all of the remaining blocks are related directly or indirectly; if the image is such that substantial errors could arise in the mean levels of the other blocks it may be desirable to transmit the do coefficients determining the mean levels of more than one block, e.g. a row or column, or possibly of a few blacks distributed throughout the image area, limiting the extent to which the effect of transmission errors can "propagate" through the image during the reconstruction process.
When the relative adjustment of the mean levels has been effected on the basis of an arbitrarily chosen value in one block selected as reference, the mean levels of all of the blocks may be subjected to a common additive correction kiwi produce a moan grew level within a given range for the entire image.
If the do coefficient of a single block is transmitted or stored to provide, when decoded, a reference for the whole image as described above it may still be desirable to adjust the mean levels to give a mean grew level within a given range for the image, although, in theory at least, such adjustment ought not to be necessary.
:9~278~7 Some embodiments of the invention will now be described with reference to the accompanying drawings, in which:
FIGURE 1 illustrates the division of an image into blocks;
FIGURE 2 shows an example of the numbers of bits allocated to each coefficient of a transformed 8 x 8 block;
FIGURE 3 is a block diagram of one example of an image transmission system using a method according to the lo invention; and FIGURE 4 is a diagram to be used to help to describe a method according to the invention.
In Figure 1, an image is shown as being divided into 64 blocks, each composed of 64 picture elements (pots). It is assumed that the number of pots in both horizontal and vertical directions is the same. As a practical example, it is likely that an image of, say, 256 x 256 Pews might be divided into 1024 8 x 8 blocs.
The image is converted into a video signal, and sampled. Each 8 x 8 array of samples corresponding to a block is subjected to a two-dimensional unitary transformation.
It is impractical to transform the entire image in a reasonable time because the calculation involved in producing the transforms of images having over 65,000 Pews are at present too lengthy even for the fastest computing techniques. Division of the image into smaller blocks, for example, consisting of 8 x 8 Pews means that the computations involved are simplified by a factor of 1,000 and can be executed in a reasonable time by present computing techniques and hardware. Suitable transforms are the Discrete Cosine Transform or the Hadamard transform, for example. The transformation produces an 8 x 8 array of coefficients (in general, an em sample array lZ27Y~6~
produces an NxM array of coefficients, although it is common to discard - or not calculate - the higher sequence coefficients). The sequence in a given direction is the number of sign changes in the corresponding row or column 5 of the basis matrix of the transform used.
Figure 2 shows the number of bits which, in a conventional system, would typically be allocated to coefficients of a transformed block of the image for transmission of that image in the transformed state, ordered as to sequence; thus the top left term indicates that 8 bits are allocated to the zero sequence term, whilst the right hand column and bottom row correspond to the highest sequence coefficient in the two directions.
Considering the block X shown in Figure 1, this block is surrounded by eight blocks A, B, C, D, E, F, G
and H, and the invention makes use of the fact that the lines of Pews of the block X adjacent its four edges will be similar in most cases to the lines of Pews of the blocs B, D, E and G adjacent the same edges. mix wit not be true if a discontinuity in the image separating areas of differing brightness lies along one of the boundary edges of the block X and a method of taking this into consideration is described below.
From a consideration of Figure 2, it will be clear that the zero-sequency, or do coefficient at the top left-hand corner, which represents the average brightness level of the whole block, is normally conveyed by ore bits than the other coefficients. However, if the do coefficient is discarded the amount of data needed to ye transmitted to convey the transformed block is reduced by one-eighth, or possibly more depending on the block size, bit allocation and transformation used. The varying detail of the part of the image within a block is conveyed by the other coefficients so that the discarding of the
2~l~6~
do coefficients does not affect the detail conveyed.
However, the discarding of the do coefficient does give rise to the difficulty that the mean brightness levels of the blocks will not automatically have the correct valves when the image is reproduced by the inverse transformation and the sharp brightness changes at the edges of the blocks will then be objectionable. It is proposed therefore to adjust the mean levels of the blocks of the reproduced image by comparing the lines of Pews belonging to adjacent blocks on each side of an edge and adjusting the mean levels so as to reduce the differences. If, for example, the do coefficient of the top left-hand bloc of the image is transmitted, then the mean levels of the adjacent blocks of the reproduced image can be derived from that transmitted do coefficient by choosing mean levels which minimize the mean square value of the brightness differences between the adjacent lines of Pews at the edges between the blocks. In this way it is possible to build up the men levels of all the blocks by reference to the one block of which the d.cA coefficient was transmitted.
Three alternative methods of building up the mean levels of the blocks over the entire image are possible, and in the following description it is assumed that the mean level of the top left-hand block, (1,1~, is either transmitted or is set to zero or some other arbitrary value. In the latter case, then an overall adjustment of the mean levels of all of the blocks by the same amount may be made at the end to bring the overall brightness level to a satisfactory value.
In a first method of building up the mean levels, the levels of the blocks along the top edge of the image are worked out in sequence and then the blocks down the left-hand edge. After that the remainder of the blocks 12278~7 are dealt with individually by reference to the differences along both of the edges which each block shares with two blocks whose mean levels are already calculated. A
second way in which the mean levels may be built up is to determine those of the blocks in the first row as described above and then to build up each subsequent row of blocks so as to minimize the edge differences both between the blocks of the row and between them and the blocks of the preceding row. The third way is to combine the blocks into sets of four and adjust the relative levels of the blocks within each set, so as to produce a set of blocks of twice the linear dimension of the original blocks and then to combine the larger blocks into four again and so on until the entire image has been processed.
Figure 3 shows in block diagrammatic form one example of a transmission system using a method of transmitting an image according to the invention. In Figure 3, a video signal is applied via a terminal 1 to a sampling circuit 2 from which the sampled analog values are applied to an analogue/digital converter 3 which preferably includes some form of non-linear quantisation to optimize the encoding to digital form. The digital values are then applied to unit 4 which applies to the values in blocks corresponding to the blocks of the image a two-dimensional unitary transformation such as, for example, a discrete cosine transformation or a Hadamard transformation. At this stage the do coefficients of most of the blocks, or possibly all of them, are not generated. The remaining coefficients are subjected to quantisation and encoding in a unit 5 as required for transmission or image. The encoding arrangements could be, for example, constructed as described in our European Patent Application No. 82303825 published on February 16, 1983 under No. 0072117, 2~367 the only difference being that the zero sequence coefficients are not calculated; or at least, not transmitted.
The stored or transmitted data is subsequently received by a decoder 6 which decodes the received data to reproduce the quantized values of the coefficients and the coefficients so obtained are grouped together into their blocks and subjected to the inverse transform to that applied by the unit 4; this inverse transform is effected by the unit 7. The decoding process is, thus far, conventional, except that zero is assumed for the missing zero sequence coefficients. Thereafter the missing mean values are calculated as described above, so that discontinuities in the mean values do not appear at the block boundaries. Finally, the regenerated image information is passed to a utilization means 9 which may, for example, be a display device. Although the stages in the manipulation of the data are shown separately in Figure 3, they may in fact be effected by means of suitable computing means instead of by units dedicated to the separate operations.
Figure 4 shows the nine blocks A to H and X of Figure 1 with the rows of Pews of the block X adjacent to the edges shared with the blocks B and D indicated respectively by references 20 and 21. Adjacent to the row 20, there is in the block B/ whose mean value is already known, a row 22 of Pews adjacent to the common edge with the block X. In the block D whose mean value is already known also a row 23 of Pews adjacent to the common edge with the block X is marked. If the values of the Pews in the row 22 are given by Yip for ill, 2, 3, ..... , n, where n is the number of Pews in the row, and xi for ill, 2,
do coefficients does not affect the detail conveyed.
However, the discarding of the do coefficient does give rise to the difficulty that the mean brightness levels of the blocks will not automatically have the correct valves when the image is reproduced by the inverse transformation and the sharp brightness changes at the edges of the blocks will then be objectionable. It is proposed therefore to adjust the mean levels of the blocks of the reproduced image by comparing the lines of Pews belonging to adjacent blocks on each side of an edge and adjusting the mean levels so as to reduce the differences. If, for example, the do coefficient of the top left-hand bloc of the image is transmitted, then the mean levels of the adjacent blocks of the reproduced image can be derived from that transmitted do coefficient by choosing mean levels which minimize the mean square value of the brightness differences between the adjacent lines of Pews at the edges between the blocks. In this way it is possible to build up the men levels of all the blocks by reference to the one block of which the d.cA coefficient was transmitted.
Three alternative methods of building up the mean levels of the blocks over the entire image are possible, and in the following description it is assumed that the mean level of the top left-hand block, (1,1~, is either transmitted or is set to zero or some other arbitrary value. In the latter case, then an overall adjustment of the mean levels of all of the blocks by the same amount may be made at the end to bring the overall brightness level to a satisfactory value.
In a first method of building up the mean levels, the levels of the blocks along the top edge of the image are worked out in sequence and then the blocks down the left-hand edge. After that the remainder of the blocks 12278~7 are dealt with individually by reference to the differences along both of the edges which each block shares with two blocks whose mean levels are already calculated. A
second way in which the mean levels may be built up is to determine those of the blocks in the first row as described above and then to build up each subsequent row of blocks so as to minimize the edge differences both between the blocks of the row and between them and the blocks of the preceding row. The third way is to combine the blocks into sets of four and adjust the relative levels of the blocks within each set, so as to produce a set of blocks of twice the linear dimension of the original blocks and then to combine the larger blocks into four again and so on until the entire image has been processed.
Figure 3 shows in block diagrammatic form one example of a transmission system using a method of transmitting an image according to the invention. In Figure 3, a video signal is applied via a terminal 1 to a sampling circuit 2 from which the sampled analog values are applied to an analogue/digital converter 3 which preferably includes some form of non-linear quantisation to optimize the encoding to digital form. The digital values are then applied to unit 4 which applies to the values in blocks corresponding to the blocks of the image a two-dimensional unitary transformation such as, for example, a discrete cosine transformation or a Hadamard transformation. At this stage the do coefficients of most of the blocks, or possibly all of them, are not generated. The remaining coefficients are subjected to quantisation and encoding in a unit 5 as required for transmission or image. The encoding arrangements could be, for example, constructed as described in our European Patent Application No. 82303825 published on February 16, 1983 under No. 0072117, 2~367 the only difference being that the zero sequence coefficients are not calculated; or at least, not transmitted.
The stored or transmitted data is subsequently received by a decoder 6 which decodes the received data to reproduce the quantized values of the coefficients and the coefficients so obtained are grouped together into their blocks and subjected to the inverse transform to that applied by the unit 4; this inverse transform is effected by the unit 7. The decoding process is, thus far, conventional, except that zero is assumed for the missing zero sequence coefficients. Thereafter the missing mean values are calculated as described above, so that discontinuities in the mean values do not appear at the block boundaries. Finally, the regenerated image information is passed to a utilization means 9 which may, for example, be a display device. Although the stages in the manipulation of the data are shown separately in Figure 3, they may in fact be effected by means of suitable computing means instead of by units dedicated to the separate operations.
Figure 4 shows the nine blocks A to H and X of Figure 1 with the rows of Pews of the block X adjacent to the edges shared with the blocks B and D indicated respectively by references 20 and 21. Adjacent to the row 20, there is in the block B/ whose mean value is already known, a row 22 of Pews adjacent to the common edge with the block X. In the block D whose mean value is already known also a row 23 of Pews adjacent to the common edge with the block X is marked. If the values of the Pews in the row 22 are given by Yip for ill, 2, 3, ..... , n, where n is the number of Pews in the row, and xi for ill, 2,
3, ..... , n represents the values of the elements of the row 20 in the block X whose mean level x is to be 3L22~367 calculated, then what is required for the mean value of the block X is a value of x' such that n , IYi- (lCi+x~) should be a minimum. It can be shown that to achieve this what is required is that n n X (I Yip inn If the differences between the Pews and the rows 21 and 23 were also to be taken into consideration in calculating the do value of the block X, then the calculation above would be modified my the addition of the value of the Pews in the rows 21 and 23 to the expressions Thus if Us and vi are the edge elements of rows 21 and 23 respectively:
n n n n (I l Yip l Xi + l Vi 5 1 Ui)/2n This corresponds to the first of the three methods outlined above ("row estimation").
In the second method (row estimation), for each row after the first the set of do coefficients is found which minimizes the sum of the square magnitudes of the edge difference vectors between that row and the previous row, and also those between the individual blocks in that row. The method of estimation of the do coefficients in the ilk row from those in the filth row is now given. It is assumed that the receiver has the following information:
2~867 (i) [u(k,Q)] it : the (i,j)th block of pots having zero do level.
(ii) ski 1 j : the (i-l,j)th block of pots whose do level have been adjusted according to the estimated do coefficients.
] ill [~l(k'Q)] ill bill j xVxVt where by 1 j is the estimated do coefficient for black ill and V=[l/n....l/n] .
Dow we are to estimate the N-dimensional do coefficient vector A = [at,...., ]
Rouge and veil j We define vertical and horizontal edge difference vectors for block it as shown in fig. 2.
m e vertical edge difference vector between the jth block and j+lth block in the ilk row of blocks is urn i j - Us l) i, Jo u(2,n)i j us Jo D .= ................. ........... j ~[l,N-l]
I Unwon) i j - Urn' l) i, Jo The horizontal edge difference vector between the (i-l,j)th block and (i,j)th block is unwell j - V(l'l)i-l,j u(n,2)i j - vow lo 20 D2,j .................. ........... j [Len]
I Unwon j - V(l,n)i~
36~
If the pots in the ilk row are adjusted by the N do coefficients at, a, Ann, then the edge difference vectors Do j and Do j are changed to W
and We j respectively:
Wl,j = Do j + (a - aj+1) x V
2,j D2,j a x V
Therefore, the sum of the squares of the magnitudes of these edge difference vectors becomes N-l e = ¦ Do judge - agile) x V¦ 2 Jo + ,5 ¦ Do j + a x Al Jo 0 Rewriting in the form of e = ¦ D j + [Rip jxA ¦
pal Jo it can be shown that e is minimum when A= -[RR] x C
pal I Pi ~27867 lo x _ 0 -1 2 and C= 2 [R] Ed pal Jo Pi Pi The evaluation of the restoration schemes was carried out experimentally using computer simulation. me head and shoulder picture of a girl was first divided into blocks of size n by n. Each block was then transformed using the Walsh/Madamard transform, and the do coefficient set equal to zero. All blocks were then inverse transformed to return to the picture domain. The o three do coefficient restoration schemes were then applied to obtain the restored pictures as well as the sets of estimated do coefficients. m eye procedures were repeated for block sizes 4x4, 8x8 and 16x16. Jo coefficient qUantizatiQn was undertaken.
With a 4x4 block size, there were edging effects in all the three restored pictures. Furthermore, the accumulation of error due to each estimation produced impairment effects along the direction of estimation. In the picture restored by element estimation, if a block was very bright or very dark, this brightness or darkness tended to diffuse diagonally from top to bottom right. In the picture restored by row estimation, the diffusion runs vertically ~2~78~7 from top to bottom and is less severe than that occurring with element estimation. In contrast, the picture restored by the third method (plane estimation) did not exhibit this effect. However, accumulation of estimation errors makes the edging effects more prominent as the block size increases.
With the 8x8 block size, pictures restored by element and row estimation still had edging effects but no apparent diffusion effect. noticeable edging effects still remained in the picture restored using plane estimation. Using a block size 16x16, row estimation restored the picture without perceptible error whilst element estimation produced a reasonably good picture.
Again, there were noticeable edging effects in the picture restored by plane estimation.
As mentioned above, the calculations assume that no severe luminance discontinuities appear in the image coincident with the edges between the blocks. If such discontinuities exist, they could be detected when the blacks are first formed before the transformation is carried out and an indication could be transmitted with the transform coefficients for a black to indicate that the differences between the Pews along one edge and those of the adjacent block should be ignore because the image has a boundary at that place. A single such transition will not obstruct the "building up" processes discussed above, but two such transitions on a given block may do so in instances where the building up process used Peg the first of the three described) relies upon the boundaries with two adjacent block to evaluate the mean level of the block in question. This situation may be met by providing that the do coefficient be transmitted in respect of the two blocks whose common boundary coincides with the ~L2~713~7 luminance discontinuity; either in every case, or in those cases where a problem is recognized on the basis of an appropriate criterion - erg the occurrence of two discontinuities. The actual criterion used would depend on the degree of sophistication of the building-up process; for example the number of occasions on which transmission of the do term was required would be less if one employed a building-up process which could approach the block in question in two directions.
The correction of differences between Pews along the edges of blocks can also be effected by arranging that all of the blocks overlap the adjacent blocks by one row or column of elements so that the blocks of restored samples after inverse transform has been applied will have samples in kimono with the adjacent blocks and the relative adjustment of the mean levels of the blocks can be achieved simply because the common samples should have the same values in both blocks. There is no value in using this technique solely to permit do term regeneration, since the redundancy would nullify the advantage obtained in reducing the amount of data needed to be transmitted to convey an image using the present invention; however, if the overlap technique is in any event used to counteract the "blocXin~" effect of omission us of coarse quantisation of the higher sequence coefficients, it provides a ready aid to reconstruction of the omitted do term.
The Hadamard transformation represents something of a special case, since its low sequence coefficients define the mean levels of sub-blocks within the bloc under consideration. For example, if siege are the transform coefficients of a 16 x 16 block of PF~.c (i, j = 1 to 16), ordered as to sequence, and my q are the mean values of four 8 x 8 sub blocks, then c1 1 (the do term), 86~
at I C2 1 and at 2 are linear combinations of mull ml,2' m2,1 and my In fact clue C12~ mull ml2 5 Lc2lc2l~ Lo I Lm2lm22~ Lo I
Thus the omission of the first four coefficients of the coefficient array of the larger block has precisely the same effect as the omission of the lowest sequence coefficients of the smaller blocks, i.e. loss of the mean level information for the smaller blocks, and these can be restored on a (smaller) block by (smaller) block basis exactly as described above.
In the transmission of image data in the form of transform coefficients, it has been proposed to use different block sizes depending upon the activity within the image and this technique could be used in conjunction with the present invention.
Although the above description has assumed a single array of samples per image, obviously the same techniques could be applied to the components (RUB or luminance/colour difference) of a color image.
The technique of the present invention does not necessarily require all the coefficients for all the blocks to be received before the do coefficient restoration process can be initiated. It can also be used with the "slow" inverse transformation, described in our earlier European patent application mentioned above, in which the definition is gradually increased as more coefficients are inverse transformed and added to the previous result. Zen using the "slow" method the estimates of the do coefficients are also continually updated as the intensity levels at the block boundaries change.
n n n n (I l Yip l Xi + l Vi 5 1 Ui)/2n This corresponds to the first of the three methods outlined above ("row estimation").
In the second method (row estimation), for each row after the first the set of do coefficients is found which minimizes the sum of the square magnitudes of the edge difference vectors between that row and the previous row, and also those between the individual blocks in that row. The method of estimation of the do coefficients in the ilk row from those in the filth row is now given. It is assumed that the receiver has the following information:
2~867 (i) [u(k,Q)] it : the (i,j)th block of pots having zero do level.
(ii) ski 1 j : the (i-l,j)th block of pots whose do level have been adjusted according to the estimated do coefficients.
] ill [~l(k'Q)] ill bill j xVxVt where by 1 j is the estimated do coefficient for black ill and V=[l/n....l/n] .
Dow we are to estimate the N-dimensional do coefficient vector A = [at,...., ]
Rouge and veil j We define vertical and horizontal edge difference vectors for block it as shown in fig. 2.
m e vertical edge difference vector between the jth block and j+lth block in the ilk row of blocks is urn i j - Us l) i, Jo u(2,n)i j us Jo D .= ................. ........... j ~[l,N-l]
I Unwon) i j - Urn' l) i, Jo The horizontal edge difference vector between the (i-l,j)th block and (i,j)th block is unwell j - V(l'l)i-l,j u(n,2)i j - vow lo 20 D2,j .................. ........... j [Len]
I Unwon j - V(l,n)i~
36~
If the pots in the ilk row are adjusted by the N do coefficients at, a, Ann, then the edge difference vectors Do j and Do j are changed to W
and We j respectively:
Wl,j = Do j + (a - aj+1) x V
2,j D2,j a x V
Therefore, the sum of the squares of the magnitudes of these edge difference vectors becomes N-l e = ¦ Do judge - agile) x V¦ 2 Jo + ,5 ¦ Do j + a x Al Jo 0 Rewriting in the form of e = ¦ D j + [Rip jxA ¦
pal Jo it can be shown that e is minimum when A= -[RR] x C
pal I Pi ~27867 lo x _ 0 -1 2 and C= 2 [R] Ed pal Jo Pi Pi The evaluation of the restoration schemes was carried out experimentally using computer simulation. me head and shoulder picture of a girl was first divided into blocks of size n by n. Each block was then transformed using the Walsh/Madamard transform, and the do coefficient set equal to zero. All blocks were then inverse transformed to return to the picture domain. The o three do coefficient restoration schemes were then applied to obtain the restored pictures as well as the sets of estimated do coefficients. m eye procedures were repeated for block sizes 4x4, 8x8 and 16x16. Jo coefficient qUantizatiQn was undertaken.
With a 4x4 block size, there were edging effects in all the three restored pictures. Furthermore, the accumulation of error due to each estimation produced impairment effects along the direction of estimation. In the picture restored by element estimation, if a block was very bright or very dark, this brightness or darkness tended to diffuse diagonally from top to bottom right. In the picture restored by row estimation, the diffusion runs vertically ~2~78~7 from top to bottom and is less severe than that occurring with element estimation. In contrast, the picture restored by the third method (plane estimation) did not exhibit this effect. However, accumulation of estimation errors makes the edging effects more prominent as the block size increases.
With the 8x8 block size, pictures restored by element and row estimation still had edging effects but no apparent diffusion effect. noticeable edging effects still remained in the picture restored using plane estimation. Using a block size 16x16, row estimation restored the picture without perceptible error whilst element estimation produced a reasonably good picture.
Again, there were noticeable edging effects in the picture restored by plane estimation.
As mentioned above, the calculations assume that no severe luminance discontinuities appear in the image coincident with the edges between the blocks. If such discontinuities exist, they could be detected when the blacks are first formed before the transformation is carried out and an indication could be transmitted with the transform coefficients for a black to indicate that the differences between the Pews along one edge and those of the adjacent block should be ignore because the image has a boundary at that place. A single such transition will not obstruct the "building up" processes discussed above, but two such transitions on a given block may do so in instances where the building up process used Peg the first of the three described) relies upon the boundaries with two adjacent block to evaluate the mean level of the block in question. This situation may be met by providing that the do coefficient be transmitted in respect of the two blocks whose common boundary coincides with the ~L2~713~7 luminance discontinuity; either in every case, or in those cases where a problem is recognized on the basis of an appropriate criterion - erg the occurrence of two discontinuities. The actual criterion used would depend on the degree of sophistication of the building-up process; for example the number of occasions on which transmission of the do term was required would be less if one employed a building-up process which could approach the block in question in two directions.
The correction of differences between Pews along the edges of blocks can also be effected by arranging that all of the blocks overlap the adjacent blocks by one row or column of elements so that the blocks of restored samples after inverse transform has been applied will have samples in kimono with the adjacent blocks and the relative adjustment of the mean levels of the blocks can be achieved simply because the common samples should have the same values in both blocks. There is no value in using this technique solely to permit do term regeneration, since the redundancy would nullify the advantage obtained in reducing the amount of data needed to be transmitted to convey an image using the present invention; however, if the overlap technique is in any event used to counteract the "blocXin~" effect of omission us of coarse quantisation of the higher sequence coefficients, it provides a ready aid to reconstruction of the omitted do term.
The Hadamard transformation represents something of a special case, since its low sequence coefficients define the mean levels of sub-blocks within the bloc under consideration. For example, if siege are the transform coefficients of a 16 x 16 block of PF~.c (i, j = 1 to 16), ordered as to sequence, and my q are the mean values of four 8 x 8 sub blocks, then c1 1 (the do term), 86~
at I C2 1 and at 2 are linear combinations of mull ml,2' m2,1 and my In fact clue C12~ mull ml2 5 Lc2lc2l~ Lo I Lm2lm22~ Lo I
Thus the omission of the first four coefficients of the coefficient array of the larger block has precisely the same effect as the omission of the lowest sequence coefficients of the smaller blocks, i.e. loss of the mean level information for the smaller blocks, and these can be restored on a (smaller) block by (smaller) block basis exactly as described above.
In the transmission of image data in the form of transform coefficients, it has been proposed to use different block sizes depending upon the activity within the image and this technique could be used in conjunction with the present invention.
Although the above description has assumed a single array of samples per image, obviously the same techniques could be applied to the components (RUB or luminance/colour difference) of a color image.
The technique of the present invention does not necessarily require all the coefficients for all the blocks to be received before the do coefficient restoration process can be initiated. It can also be used with the "slow" inverse transformation, described in our earlier European patent application mentioned above, in which the definition is gradually increased as more coefficients are inverse transformed and added to the previous result. Zen using the "slow" method the estimates of the do coefficients are also continually updated as the intensity levels at the block boundaries change.
Claims (16)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of processing an image comprising:
(a) producing an array of samples representing the picture elements of an array of such elements representing an original image, notionally dividing the array of picture elements into a plurality of blocks and for each block subjecting the corres-ponding sub-array of samples to a two-dimensional transformation to produce a set of coefficients, the zero sequency coefficient being omitted from some or all of the sets, and (b) subjecting the sets of coefficients corresponding to each transformed block to the inverse of the original two-dimensional transformation to produce a sub-array of restored samples and reproducing an image from the restored samples, values for the mean levels of the blocks of the reproduced image being calculated so as to substantially minimise visible brightness changes and/or in a colour system, colour changes between the particular block and at least one of the adjacent thereto blocks.
(a) producing an array of samples representing the picture elements of an array of such elements representing an original image, notionally dividing the array of picture elements into a plurality of blocks and for each block subjecting the corres-ponding sub-array of samples to a two-dimensional transformation to produce a set of coefficients, the zero sequency coefficient being omitted from some or all of the sets, and (b) subjecting the sets of coefficients corresponding to each transformed block to the inverse of the original two-dimensional transformation to produce a sub-array of restored samples and reproducing an image from the restored samples, values for the mean levels of the blocks of the reproduced image being calculated so as to substantially minimise visible brightness changes and/or in a colour system, colour changes between the particular block and at least one of the adjacent thereto blocks.
2. A method according to claim 1 wherein the calculation of the mean levels of the blocks of the reproduced image is carried out to minimise the mean square value of the differences between the sample values of the nearest adjacent elements in different blocks at at least one of the boundaries between the blocks.
3. A method according to claim 2 wherein the mean square values of the differences between the sample values of the nearest adjacent elements in different blocks along the different boundaries between blocks of the original image are calculated and indications of which boundaries have calculated values exceeding a threshold value are associated with the representations of the coefficients, the calculation of the mean levels of the restored blocks being arranged not to take into account bright-ness differences between elements along such boundaries.
4. A method according to claim 1, 2 or 3 wherein the calculation of the mean levels of the blocks of the reproduced image is performed for one block at a time, starting from a block in respect of which the zero sequency coefficient has not been omitted, or of which the mean level is set to an arbitrary value, and taking the blocks in a sequence so that the or each block of which the mean level is being calculated at any time borders on one or more blocks of which the mean level has already been determined.
5. A method according to claim ], 2 or 3 wherein the calculation of the mean levels of the blocks of the reproduced image is performed for one block at a time until a row or column of blocks is completed, and thereafter each row or, as the case may be, column of blocks is adjusted so as to minimise brightness/colour differences both between the blocks within it and between its blocks and those of the previously processed row or column.
6. A method according to claim 1, 2 or 3 wherein the calculation of the mean levels of the blocks of the reproduced image is per-formed so as to determine the relative mean levels of the blocks of a group of four mutually contiguous blocks, then to determine the mean levels of the groups of a larger group formed of four mutually contiguous groups, progressively until the mean levels of all blocks have been determined.
7. A method according to claim 1, 2 or 3 wherein all of the zero sequency coefficients are omitted and after the mean levels of all of the blocks of the reproduced image have been calculated they are all subjected to an additive correction of the same amount so as to bring the average grey level of the entire reproduced image within a desired range.
8. A method according to claim 1, 2 or 3 wherein in which the zero sequency coefficients are retained only in respect of one row or column of blocks.
9. A method of processing an image comprising:
(a) producing an array of samples representing the picture elements of an array of such elements representing an original image;
subjecting the array of samples to a two-dimensional Hadamard transformation to produce a set of coefficients, the zero and first order sequency coefficients being omitted;
(b) subjecting the set of coefficients to an inverse Hadamard transformation to produce an array of restored samples;
and reproducing an image from the restored samples, values for the omitted coefficients to be used in the inverse transforma-tion being calculated so as to substantially minimise visible brightness changes and/or in a colour system, colour changes across at least some of the boundaries between blocks of the reproduced image which correspond to the omitted coefficients.
(a) producing an array of samples representing the picture elements of an array of such elements representing an original image;
subjecting the array of samples to a two-dimensional Hadamard transformation to produce a set of coefficients, the zero and first order sequency coefficients being omitted;
(b) subjecting the set of coefficients to an inverse Hadamard transformation to produce an array of restored samples;
and reproducing an image from the restored samples, values for the omitted coefficients to be used in the inverse transforma-tion being calculated so as to substantially minimise visible brightness changes and/or in a colour system, colour changes across at least some of the boundaries between blocks of the reproduced image which correspond to the omitted coefficients.
10. An apparatus for reproducing an image comprising inverse transforming means for receiving sets of coefficients produced by applying a two-dimensional transformation to sub-arrays of an array of samples representing the picture elements of an original image, each sub-array corresponding to a block of the image, some or all of which sets having the zero sequency coefficient omitted therefrom, the image transforming means being arranged to subject the set of coefficients corresponding to each block to the inverse of the original two-dimensional transformation to produce a sub-array of restored samples, and means for reproducing an image from the restored samples including means for calculating values for the mean levels of the restored blocks so as to substantially minimise visible brightness changes and/or in a colour system, colour changes between the particular block and at least one of the neighbour-ing blocks, the calculating means being operable to calculate such values for blocks including blocks which are adjacent only to blocks for which the zero sequency coefficient has been omitted.
11. An apparatus according to claim 10 wherein the calculating means is arranged in operation to calculate the mean levels of the blocks of the reproduced image so as to minimise the mean square value of the differences between the sample values of the nearest adjacent elements in different blocks at at least one of the boundaries between the blocks.
12. An apparatus according to claim 11 wherein the calculating means is arranged to respond to indications identifying those boundaries between blocks of the original image in respect of which the mean square values of the differences between the sample values of the nearest adjacent elements in different blocks along the respective boundary exceed a threshold value and not to take into account brightness differences between elements along such boundaries when calculating the mean levels of the restored blocks.
13. An apparatus according to claim 10, 11 or 12 wherein the calculating means is arranged in operation to determine the mean levels of the blocks of the reproduced image for one block at a time, starting from a block in respect of which the zero sequency coefficient has not been omitted, or of which the mean level is set to an arbitrary value, and taking the blocks in a sequence so that the or each block of which the mean level is being calculated at any time borders on one or more blocks of which the mean level has already been determined.
14. An apparatus according to claim 10, 11 or 12 wherein the calculating means is arranged in operation to determine the mean levels of the blocks of the reproduced image is performed for one block at a time until a row or column of blocks is completed, and thereafter to adjust each row or, as the case may be, column of blocks so as to minimise brightness/colour differences both between the blocks within it and between its blocks and those of the previously processed row or column.
15. An apparatus according to claim 10, 11 or 12 wherein the calculating means is arranged in operation to determine the relative mean levels of the blocks of a group of four mutually contiguous blocks, then to determine the mean levels of the groups of a larger group formed of four mutually contiguous groups, progressively until the mean levels of all blocks have been determined.
16. An apparatus according to claim 10, 11 or 12 for use when all of the zero sequence coefficients are omitted, the apparatus being arranged ion operation, after the mean levels of all of the blocks of the reproduced image have been calculated to subject them all to an additive correction of the same amount so as to bring the average grey level of the entire reproduced image within a desired range.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8229420 | 1982-10-14 | ||
| GB8229420 | 1982-10-14 |
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| CA1227867A true CA1227867A (en) | 1987-10-06 |
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| CA000438840A Expired CA1227867A (en) | 1982-10-14 | 1983-10-12 | Image transmission |
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| EP (1) | EP0107426B1 (en) |
| JP (1) | JPH07118803B2 (en) |
| AT (1) | ATE25177T1 (en) |
| AU (1) | AU566509B2 (en) |
| CA (1) | CA1227867A (en) |
| DE (1) | DE3369451D1 (en) |
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| DE3513074A1 (en) * | 1985-04-12 | 1986-10-23 | Telefunken Fernseh Und Rundfunk Gmbh, 3000 Hannover | DIGITAL MESSAGE TRANSMISSION METHOD |
| JPS61294586A (en) * | 1985-06-21 | 1986-12-25 | Nec Corp | Conversion coding and decoding device for picture signal |
| JPS61294585A (en) * | 1985-06-21 | 1986-12-25 | Nec Corp | Convertion coding system for picture signal |
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| EP0227956B1 (en) * | 1985-12-04 | 1990-04-25 | Siemens Aktiengesellschaft | Vector quantization data reduction method of digital picture signals |
| JPS62150475A (en) * | 1985-12-24 | 1987-07-04 | Konishiroku Photo Ind Co Ltd | Picture processor |
| NL8601447A (en) * | 1986-06-05 | 1988-01-04 | Philips Nv | METHOD AND DEVICE FOR RECORDING AND / OR PLAYING VIDEO INFORMATION IN RESPECT OF A RECORD CARRIER, AND OBTAINING A RECORD CARRIER ACCORDING TO THE METHOD |
| JP2608400B2 (en) * | 1986-06-16 | 1997-05-07 | 富士写真フイルム株式会社 | Image reconstruction method from compressed image data |
| US4931954A (en) * | 1986-06-30 | 1990-06-05 | Kabushiki Kaisha Toshiba | Image storage system and method of storing images such that they are displayed with gradually increasing resolution |
| DE3626916A1 (en) * | 1986-08-08 | 1988-02-11 | Thomson Brandt Gmbh | METHOD FOR TRANSMITTING A VIDEO SIGNAL |
| DE3735349A1 (en) * | 1986-10-18 | 1988-04-28 | Toshiba Kawasaki Kk | Image compressor |
| US4849810A (en) * | 1987-06-02 | 1989-07-18 | Picturetel Corporation | Hierarchial encoding method and apparatus for efficiently communicating image sequences |
| JP2674059B2 (en) * | 1988-02-09 | 1997-11-05 | キヤノン株式会社 | Color image data transmission method |
| US4914508A (en) * | 1988-04-27 | 1990-04-03 | Universal Video Communications Corp. | Method and system for compressing and statistically encoding color video data |
| US4847677A (en) * | 1988-04-27 | 1989-07-11 | Universal Video Communications Corp. | Video telecommunication system and method for compressing and decompressing digital color video data |
| US4843466A (en) * | 1988-04-27 | 1989-06-27 | Universal Video Communications Corp. | Method and system for decompressing color video slope encoded data |
| US4849807A (en) * | 1988-04-27 | 1989-07-18 | Universal Video Communications Corp. | Method and system for compressing color video feature encoded data |
| US4857993A (en) * | 1988-04-27 | 1989-08-15 | Universal Video Communications Corp. | Method and system for decompressing digital color video statistically encoded data |
| US4816901A (en) * | 1988-04-27 | 1989-03-28 | Universal Video Communications Corp. | Method and system for compressing color video data |
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| US5473376A (en) * | 1994-12-01 | 1995-12-05 | Motorola, Inc. | Method and apparatus for adaptive entropy encoding/decoding of quantized transform coefficients in a video compression system |
| US5872572A (en) * | 1995-12-08 | 1999-02-16 | International Business Machines Corporation | Method and apparatus for generating non-uniform resolution image data |
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| US3984626A (en) * | 1975-08-01 | 1976-10-05 | Bell Telephone Laboratories, Incorporated | Picture signal coder |
| FR2329124A1 (en) * | 1975-10-24 | 1977-05-20 | Telecommunications Sa | MATRIX-TRANSFORMED IMAGE ENCODER-DECODER WITH WEIGHTING OF THE CONTRIBUTIONS OF THE IMAGE POINTS TO THE FORMATION OF THE TRANSFORMATION |
| US4189748A (en) * | 1977-08-23 | 1980-02-19 | Northrop Corporation | Video bandwidth reduction system using a two-dimensional transformation, and an adaptive filter with error correction |
| US4281344A (en) * | 1980-05-02 | 1981-07-28 | Bell Telephone Laboratories, Incorporated | Video interframe transform coding technique |
| JPS5724180A (en) * | 1980-07-18 | 1982-02-08 | Matsushita Electric Ind Co Ltd | Orthogonal conversion decoder |
| JPS57146345A (en) * | 1981-03-04 | 1982-09-09 | Toshiba Corp | 3n-th degree orthogonal transformation and inverse transformation system |
| GB2103455A (en) * | 1981-07-22 | 1983-02-16 | Post Office | Method of transmitting an image and apparatus for carrying out the method |
| US4517597A (en) * | 1982-09-14 | 1985-05-14 | New York Institute Of Technology | Method and apparatus for encoding and decoding video |
-
1983
- 1983-10-06 AT AT83306067T patent/ATE25177T1/en active
- 1983-10-06 DE DE8383306067T patent/DE3369451D1/en not_active Expired
- 1983-10-06 EP EP83306067A patent/EP0107426B1/en not_active Expired
- 1983-10-10 AU AU20017/83A patent/AU566509B2/en not_active Ceased
- 1983-10-12 CA CA000438840A patent/CA1227867A/en not_active Expired
- 1983-10-14 US US06/541,932 patent/US4633296A/en not_active Expired - Lifetime
- 1983-10-14 JP JP58191072A patent/JPH07118803B2/en not_active Expired - Lifetime
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| ATE25177T1 (en) | 1987-02-15 |
| AU2001783A (en) | 1984-04-19 |
| JPS59132291A (en) | 1984-07-30 |
| JPH07118803B2 (en) | 1995-12-18 |
| EP0107426B1 (en) | 1987-01-21 |
| US4633296A (en) | 1986-12-30 |
| EP0107426A1 (en) | 1984-05-02 |
| DE3369451D1 (en) | 1987-02-26 |
| AU566509B2 (en) | 1987-10-22 |
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