CA1162296A - Error concealment in digital television signals - Google Patents
Error concealment in digital television signalsInfo
- Publication number
- CA1162296A CA1162296A CA000386031A CA386031A CA1162296A CA 1162296 A CA1162296 A CA 1162296A CA 000386031 A CA000386031 A CA 000386031A CA 386031 A CA386031 A CA 386031A CA 1162296 A CA1162296 A CA 1162296A
- Authority
- CA
- Canada
- Prior art keywords
- sample
- signal
- algorithm
- sample signal
- horizontal line
- 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
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/64—Circuits for processing colour signals
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/64—Circuits for processing colour signals
- H04N9/646—Circuits for processing colour signals for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/79—Processing of colour television signals in connection with recording
- H04N9/87—Regeneration of colour television signals
- H04N9/88—Signal drop-out compensation
- H04N9/888—Signal drop-out compensation for signals recorded by pulse code modulation
Abstract
ABSTRACT OF THE DISCLOSURE
A method of concealing errors in a composite PAL or NTSC digital television signal formed of sample signals corresponding respectively to sample positions along horizontal scan lines of a television picture made up of a plurality of such horizontal lines, comprises, in respect of each sample signal, using a first algorithm to calculate a first expected value of the sample signal, the first algorithm using actual values of adjacent sample signals in the same horizontal line as the sample signal, using a second algorithm to calculate a second expected value of the sample signal, the second algorithm using actual values of adjacent sample signals in the same horizontal line as the sample signal and actual values of adjacent sample signals in the horizontal lines preceding and following the horizontal line of the sample signal, continously monitoring which of the first and second algorithms gives expected values closer to the actual values, and on occurrence of an error sample signal using the algorithm currently giving the better result to calculate a corrected sample signal to be substituted for the error sample signal.
A method of concealing errors in a composite PAL or NTSC digital television signal formed of sample signals corresponding respectively to sample positions along horizontal scan lines of a television picture made up of a plurality of such horizontal lines, comprises, in respect of each sample signal, using a first algorithm to calculate a first expected value of the sample signal, the first algorithm using actual values of adjacent sample signals in the same horizontal line as the sample signal, using a second algorithm to calculate a second expected value of the sample signal, the second algorithm using actual values of adjacent sample signals in the same horizontal line as the sample signal and actual values of adjacent sample signals in the horizontal lines preceding and following the horizontal line of the sample signal, continously monitoring which of the first and second algorithms gives expected values closer to the actual values, and on occurrence of an error sample signal using the algorithm currently giving the better result to calculate a corrected sample signal to be substituted for the error sample signal.
Description
BACKGROUND OF THE ~NVENTlON
Field of the Invention This invention relates to error concealment in digital television signals, and more particularly in composite PAL or NTSC digital television s i gnals .
Description of the Prior Art Recently there has been an increasing interest in the use of digital techniques for television signals. Such techniques are, for example, used in some video tape recording arrangements where an incorning television signal to be recorded is sampled, the samples are coded into digital form, the digital data signals are recorded and subsequently reproduced by a video tape` recorder (VTR), the reproduced digital data signals are decoded, and the decoded signals are used to form an analog signal correspondiny to the original television signal.
If errors occur in the handling of the digital signals, for example due - to noise or drop-out occurring in the VTR, the digital signals are corrupted and then the reformed television signal does not correspond exactly to the original television signal, and a resulting television picture is degraded.
There are two main approaches to dealing with errors in digital television signals. The first approach is correction, which involves the production and use of additional data signals purely for the purposes of error detection and correction, these additional data signals otherwise being redundant. While correction provides good results, it cannot generally be used as the sole means of dealing with errors, because a oomprehersive correction capability would require an excessive amount of additional data _ which might overload the data handling paths or raise the data rate to an unacceptable level. The second approach, with which the present invention is more particularly concerned, is concealment. This comprises the .....
replacement of corrupted data signals by data signals generated using available uncorrupted data signals. This method relies largely for accuracy ',3 ~ ' .
on the strong correla~ion that exists in a television signal.
- SUMMARY OF THE INVENTI(~N
_~ One object of the present invention is to provide an improved method and apparatus for concealing errors in digital television signals.
Another object of the present invention is to provide a method and - I apparatus for concealing errors in digitai television signals using selection of one correction algorithm from two correction algorithms.
__ r Another object of the present invention is to provide a method and apparatus for concealing errors in digital television signals using sample L lo values which are adjacent to an error sample value.
According to the present invention there is provided a method of . concealing errors in a composite PAL or NTSC digital television signal, which television signal comprises a plurality of sample signals corresponding respectively to sample positions along a horizontal scan line of a television - 15 picture made up of a plurality of said horizontal linesS the method comprising, in respect of each said sample signal:
_~ , using a first algorithm to calculate a first expected value of said sample signal, said first algorithm using actual values of adjacent sample signals in the sarne horizontal line as said sample signal for said calculation;
2û performing a first comparison between said first expected value and the actual value of said sample signal;
using a second algorithm to calculate a second expected value of said sample signal, said second algorithm using actual values of adjacent sample signals in the same horizontal line as said sample signal and actual values of 25 adjacent sample signals in the horizontal lines preceding and following the horizontal line of said sample signal;
performing a second comparison between said second expected value and the actual value of said sample signal;
continuously storing an indication as to which of said ~irst and second 30 cornparisons gives the closer result; and ~p l on occurrence of an error sample signal substituting a corrected sample signal for said error sample signal so as to conceal the error, said corrected sample signal being generaled using said first or second algorithm in dependence on said indication.
According to the present invention there is also provided apparatus for concealing errors in a composite PAL or NTSC digital television signal, which te!evision signal comprises a plurality of sample signals corresponding _ respectively to sample positions along a horizontal scan line of a television picture made up of a plurality of such lines, the apparatus comprising:
means operative in respect of each said sample signal to use a first algorithm to calculate a first expected value of said sarople signal, said firstalgorithm using actual values of adjacent sample signals in the same ~" .
horizontal line as said sample signal for said calculation;
means for performing a first comparison between said first expected value 15 and the actual value of said sample signal;
means operative in respect of each said sample value to use a second algorlthm to calculate a second expected value of said sample signal, said second algorithm using actual values of adjacent sample signals in the same horizontal line as said sample signal and actual values of adjacent sample 20 signals in the horizontal lines preceding and following the horizontal line of said sample signal;
. means for perforrning a second comparison between said second expected -~
value and the actual value of said sample signal;
means for continuously storing an indlcation as to which of said first and 25 second comparisons gives the closer result; and means operative on occurrence of an error sarnple signal to substitute a _ corrected sample signal for said error sample signal so as to corlceal the error, said corrected sample signal being generated using said first or second .
algorithm in dependence on said indication.
The above, and other objects, features and advantages of the invention will be apparent from the following detailed description of illus~rative embodirnents which is to be read in connection with the accompanying drawings.
BRlEF DESCRIPTlON OFTHE DRAWINGS
Figures 1 to 4 show respective parts of a matrix of sample positions ¦ in one field of a composite PAL digital television signal;
Figure 5 shows in block form an embodiment of apparatus for concealing errors in a composite PAL or NTSC digital television signal and 10 according to the invention; and Figures 6 and 7 show respective parts of a matrix of sample positions in one field of a composite NTSC digital television signal.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The m0thod and apparatus to be described are for error concealment 15 in a composite PAL or NTSC digital television signal. Consideration will first be given to a PAL signal~ and the modifications for an NTSC signal will then be considered. The sarnpling frequency used to sarnple the analog PAL
television signal is approximately 8.B Megahertz, and as this is twice th color sub-carrier frequency of the television signal the resulting data is 20 sometimes referred to as 2fSC data. At this sampling frequency the Nyquist frequency is approximately 4.4 Megahertz which is below the maximum frequency of 5.5 Megahertz to be sampled, so the system is sub-Nyquist and in theory frequencies above approximately 4.4 Megahertz cannot be reproduced. In practice, however, by use of suitable two-dimension filtering 25 higher frequencies can be reproduced. This is explained in more detail in :
IBA Technical Review, No.12~ pp 3 to 1~.
_ i Referring to Figure 1 this shows part of a matrix of sample positions in one field of a television picture, four consecutive horizontal scan lines of the picture being shown. The sample positions are disposed at regular 3û intervals along each of the lines, the intervals corresponding to the sampling . I
frequency of approximately 8.8 Megahertz, and the sample positions in alternate lines are aligned in the vertical direction. In adjacent lines the sample positions are off-set by half the interval, so that viewed in the -vertical direction the sarnple positions in one line ~all mid-way between the 5 sample positions in the lines immediately above and below. Thus the overall pattern is diagonal rather than orthogonal.
Moreover, if the chrominance component of each sample is taken as __ C9 then the actual samples alternate c, -c, c, -c, ...... in say even-numbered lines. In the odd-numbered lines also the samples alternate in sign, and are 10 in fact jc, -jc, jc, -jc, ... For convenience, and for ready comparison with the NTSC sample matrices described below, the samples are designated cn, ~cr~, ... cn+1, -cn+1, ... etc., the suffices corresponding to the line numbers, in Figures 1, 3 and 4. Due to the PAL quarter-line off-set the positive and negative samples in the even-numbered lines and in the odd-numbered lines - 15 also alternate in the vertical direction, so the pattern ir dicated in Figure 1 .~' .;: repeats at four line intervals. The PAL 25 Hertz off-set results in only a , . j .
_~ ; srnall error in embodiments of the invention and will therefore be ignored.
Reading from the top, consecutive lines are denoted n-2, n-1, n, n~1, ..., and reading from the left consecutive sample positions in the odd-20 numbered lines are denoted.. S-2, S-1, S, S+1, 5+2, .. ...and in the odd-numbered lines are denotedS-22, S-1~, S-~, S+~, 5+12, 5+2~, Using this notation~ any sample position in the matrix can be designated by the line and sample number, so sample ,oosition n, S is in line n at position S.
.~ The concealment method operates using two algorithms each of 25 which is used oontinuously to calculate expected sample values at each sample position from the known sample values at near-by sample positions.
_ Each expected value is then compared with the actual sample value at that position and an indication of which algorithm is producing expected values closer to the actual values at any time is stored. Then, on occurrence of an 30 error sarnple, the algorithm currently giving the closer values is used to fi ~3~,~ ! ~7~
.
calculate a corrected sample value which is thel~ substituted in place of the error sample.
The ~act that there is an error at a given sample posil ion can be determined in any suitable manner, and the manner used is not oF critical 5importance to the concealment method nuw being described. Briefly, however, and purely by way of example, it may be determined that the data ¦ word representing the sample value is not valid. As a more specific __ example, suppose that each sample value is coded into a word in the sub-set of 10-bit words which consist of 5 "0" and 5 "1"; this being convenient for L lomagnetic recording and reproduction because of the large number of transients and the ease of clock recovery. In this case any reproduced data word not having 5 "û" and 5 "1" is not a valid member of the sub-set and so is clearly an error. Thereupon a flag signal indicating an error sample is generated.
15The two algorithms used will now be described, and they will be designated as algorithms A1 and A2.
The first algorithm A1 uses a simple averaging technique whereby the expected sample value at a given sample position is calculated by averaging the actual sample values at the next-but-one sample positions before and 20after the given sample position in the same horizontal line. The next-but-- one sample positions are used, rather than the imrnediately adjacant ones partly to reduce the chance of the sample values used for the algorithm also - themselves being in error, but also to avoid problems resulting from the . alternating signs of the chrominance component.
25If then AlV is an expected sample value calculated using the algorithm A1 and AV is an actual sample value, then the algorithm A1 may be represented as:
AlV(n, S) = 1 AV(n, S-2) + 2 AV(n, S~2) This is also illustrated in Figure 2 from which it will be seen that the algorithm A1 will continue to produce appropriate expected sample values as the sample position for which the calculation is being per~ormed steps _ ~
along the horizontal line n. Reference to Figure 3 will show that this is also 5 true of the odd-numbered lines. In other words the algorithm Al is independent of the values of n and S.
. ~ . i The algorithm A1 has very good vertical resolution9 but the _ I horizontal resolution is relatively poor and indeed it can be shown that there are circumstances where concealrnent based exclusively on the algorithm A1 10 produces worse results in a television picture than no concealment at all.
It will be noted that the algorithm A1 is a one-dimensional algorithm, . . .
as it uses sample values from a single horizontal line. The algorithm A2, on the other handl uses sample values from three consecutive horizontal lines and has good horizontal resolution. The sample values used are those at the 15 eight sample positions nearest to the given sample position and a summation is used which takes into account the signs of the sample values. ~ing the --~ same notation as before, the algorithm A2 may be represented as:
A2V(n, S) = 3- AV(n-1, 5~ 2) ~ 8 AV(n-1, 5+ 12) + B AV(n, S-2) - 3 AV(n, S-1) .
~.., . ~
3 AV(n, S+1) + 18 AV(n, S+2) . ... -j .
~'-+ 3 AV(n~1, S- 2) + 3 AV(n+1, 5+ 2) : .
--l This is also illustrated in Figure 4 from which it will be seen that in the particular example shown therein, and due to the signs of the sample values . .
and the signs used in the algorithm A2, the algorithm A2 sums to "cn".
30 Likewise when the next sample position S+1 to the right in the same 32Z~:~
horizontal line n is considered, it sums to "-cn". Likewise for the sarnple position n+l, S+ 2J for example, it sums to "cn+l'l as required. In other words the algorithm A2 is also independent of the values of n and S.
Although in describing the algorithms Al and A2 particular consideration has been given to the chrominancf~ components, it will be apparent from the fact that in both the algorithms Al and A2 the - ¦ coefficients sum to unity, that they are also appropriate for luminance _ components. Thus for a flat grey field, for example, it will be seen that the algorithms Al and A2 will give correct values for AlV and A2V respectively.
Referring to Figure 5, this shows apparatus for concealing errors in a PAL digital television signal. The apparatus comprises a sample storage rneans 1 to which input samples which may, for example, have been reproduced from a digital VTR are supplied by way of an input terrninal 2.
The sample storage means 1 supplies outputs to a sample matrix storage means 3 which stores a moving matrix of sample values corresponding to the sample positions n-l, 5~ 2; n-l, 5~ 1; n, 5-2; n, S-l; n, 5; n, 5~1; n, 5+2; n~l, ' S- 2; and n+l3 5+ 2 Part of the output of the sample matrix storage means 3 is supplied to an Al algorithm calculation circuit 4 which for each sample position calculates the expected sample value AlV and supplies it to a comparison circuit 4 where it is compared with the actual value AV. This comparison results in an error signal, the magnitude of which represents the error i ~. ., between the estimated sample value AlV and the actual sample valuP AV7 this error signal being supplied to an algorithm selection circuit 6.
The output of the sample matrix storage n~eans 3 is supplied to an A2 ~ algorithm calculation circuit 7 whicl for each sample position calculàtes the - expected sample value A2V and supplies it to a cDmparison circuit 8 where it is compared with the actual sample value AV. This comparison results in a further error signal, the magnitude of which represents the error between the estimated sample value A2V and the actual sample value AV, this further error signal also ~eing supplied to the algorithm selection circuit 6.
On the basis of the rnagnitudes of the error signals supplied to it, the algorithm selection circuit 6 selects the alyorithm A1 or A2 which at that _ ~
given moment is resulting in more accurate estirnated sample values, and an 5 indication of the algorithm A1 or A2 so selected is stored in a storage means . 9.
The indication stored in the storage means 9 is supplied to a sample value calculator 10 to which the output of the sample matrix storage means 3 is also supplied, the sample value calculator 10 calculating an estimated 10 sample value A1V or A2V in dependence on the algorithm A1 or A2 currently .
indicated in the storage means 9. This estimated sample value AlV or A2V
is supplied to a switching circuit 11. The input samples supplied to the input terminal 2 are also supplied by way of timing circuits 12 to the switching circuit 11.
Normally, the input samples supplied from the input terminal 2 by way of the timing circuits 12 will be supplied by the switching circuit 11 to an output terminal 13 Howevsr, on the occurrence of an error an error flag signal is supplied to a terminal 14 connected to the switching circuit 11 and causes the switching circuit 11 to switch so as to substitute the estimated 20 sample value A1V or A2V for the error sample value in the sample values supplied to the output terminal 13.
Various refinements and extensions of the method and apparatus are of course possible. For example, in the above description it has been - ~-- assumed that the algorithm A1 or A2 is selected by a simple comparison of 25 the accuracy of the estimated sample values A1V and A2V with the actual .r''~ sample value AV. In certain circumstances, however, it may be expected that one or other of the algorithms A1 or A2 will give a more accurate result, and in this case rather than a simple comparison, some weighting of one or other of the algorithms A1 or A2 may be introduced.
It will be understood that the timing circuits 12 operate so that the estimated sarnple value A1V or A2V which is used will normally be one based on the last available sample values prior to the sample yalue which is in error. Howe~er, at any given time at least one complele field of sample values is available for signal processing, and it is not therefore essential to use an estimated sample value AlV or A2V based on actual sarnple values preceding the sample value which is in error, as an estimated sample value AlV or A2V based on actual sample values subsequent to the error sample _ value may alternatively, or in additinn, be used.
The modifications necessary in the case of a composite NTSC digital 10 television signal will now be cor sidered. The sampling frequency used to sample the analog NTSC television siynal is approximately 7.2 Megahertz, the actual frequency being twice the color sub-carrier frequency f'sc of the television signal, minus or plus one quarter of the line scan frequency fH.
At this sampling frequency the Nyquist frequency is approximately 15 3.6 Megahertz which is below the maximum frequency of 4.5 Megahertz to - be sampled, so again the system is sub-Nyquist and in theory frequencies above 3.6 Megahertz cannot be reproduced. This is explained in more detail in SMPTE Journal, January 1976~ in an article "Sub-Nyquist encoding of PCM NTSC color television" by John Rossi.
Referring to Figures 6A and 6B, these show parts of matrices of sample positions in one field of a television picture, five consecutive horizontal scan lines of the picture being shown, for sampling freque~ecies of f'SC-2;fH and f'Sc+~fH respectively. The sample positions are disposed at regular intervals along each of the lines, the intervals corresponding to the 25 sampling frequency of approximately 7.2 Megahertz, and the sample _ positions in every fourth line are aligned in the vertical direction. In adjacent lines the sample positions are off-set by one quarter of the interval. Thus again the overall pattern is diagonal rather than orthogonal.
Moreover, as with a PAL signal, if the chrorninance component of 30 each sample is taken as c, then the actual samples alternate c, -c, c~ -c, .~
in say even-numbered lines. In the line n, for example, the samples are designated c7n, ~c'n, c'n, -c'n, ... In odd-numbered lines the samples again alternate in sign and are designated c n-1~ c n-1~ -- c n*1~ n+1~
-- with the PAL sample matrix, the pattern repeats at four line intervals.
Reading from the top, consecutive lines are again denoted n-2, n-1, n, n+1, ..., and reading from the left consecutive sarnple positions in the line n are denoted ... S-2, S-1, S, 5+1, 5+2, ..., and sirnilarly for the other lines as indicated, having in mind that in this case the off-set between adjacent lines is one quarter.
As for a PAL signal, two algorithms are used, and the first is the algorithm A1 described above.
The second algorithm takes one of two forms depending on the sampling frequency. For the sampling frequencies f'Sc-~fH and f'sc+-~f the second algorithm is designated A'2 and A"2 respectively. In both cases _ 15 the sample values used are those at eight near-by sample positions and a ; summation is used which takes into account the signs of the sample values.
.~ I Using the same notation as before, the algorithm A'2 may be represented as:
A'2V(n, S) = 3 AV(n-1, S- 3) -~ 3 AV(n-l, S+ 1~) + 18 AV(n,~S-2) 3 AV(n, S-1) .
- 3 AV(n, 5+1) f 8 AV(n, S+2) .. . .. .
25+ 3 AV(n+17 S- 4) + 3 AV(n+1, S+ 3) _ l This is also illustrated in Figure 7A, while Figure 7B illustrates the algorithm A"2, which may be represented as:
30A"2V(n, S) = 3 AV(n-1, 5~ 4) + 8 AV(n-1, S+ 3) ~ P ~ 229Çci + 8 AV(n, 5-2) - 3 AV(n, S-1) - 3 AV(n, 5+1) ~ 8 AV(n, S~2) ~ 8 AV(n+1, S- 4) + 3 AV(n~1, S+ 1) .
It will be apparent that the apparatus of Figure 5 requires modification for an NTSC digital te!evision signal. In particular, the moving matrix of sample values supplied by the sample storage means 1 is 10 appropriately modified, and the algorithm calculation circuit 7 calculates the algorithm A'2 or A"2 as appropriate.
The invention is not limited to concealment of errors which have arisen in the course of recording and reproducing from a VTF;!, but may be used in any situation where errors have arisen in processing, transmitting or 15 handling a composite PAL or NTSC digital television signal.
- - Although illustrative embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications can be effected 20 therein by one skilled in the art without department from the scope and spirit of the invention as defined by the appended claims.
. . I , ..;,
Field of the Invention This invention relates to error concealment in digital television signals, and more particularly in composite PAL or NTSC digital television s i gnals .
Description of the Prior Art Recently there has been an increasing interest in the use of digital techniques for television signals. Such techniques are, for example, used in some video tape recording arrangements where an incorning television signal to be recorded is sampled, the samples are coded into digital form, the digital data signals are recorded and subsequently reproduced by a video tape` recorder (VTR), the reproduced digital data signals are decoded, and the decoded signals are used to form an analog signal correspondiny to the original television signal.
If errors occur in the handling of the digital signals, for example due - to noise or drop-out occurring in the VTR, the digital signals are corrupted and then the reformed television signal does not correspond exactly to the original television signal, and a resulting television picture is degraded.
There are two main approaches to dealing with errors in digital television signals. The first approach is correction, which involves the production and use of additional data signals purely for the purposes of error detection and correction, these additional data signals otherwise being redundant. While correction provides good results, it cannot generally be used as the sole means of dealing with errors, because a oomprehersive correction capability would require an excessive amount of additional data _ which might overload the data handling paths or raise the data rate to an unacceptable level. The second approach, with which the present invention is more particularly concerned, is concealment. This comprises the .....
replacement of corrupted data signals by data signals generated using available uncorrupted data signals. This method relies largely for accuracy ',3 ~ ' .
on the strong correla~ion that exists in a television signal.
- SUMMARY OF THE INVENTI(~N
_~ One object of the present invention is to provide an improved method and apparatus for concealing errors in digital television signals.
Another object of the present invention is to provide a method and - I apparatus for concealing errors in digitai television signals using selection of one correction algorithm from two correction algorithms.
__ r Another object of the present invention is to provide a method and apparatus for concealing errors in digital television signals using sample L lo values which are adjacent to an error sample value.
According to the present invention there is provided a method of . concealing errors in a composite PAL or NTSC digital television signal, which television signal comprises a plurality of sample signals corresponding respectively to sample positions along a horizontal scan line of a television - 15 picture made up of a plurality of said horizontal linesS the method comprising, in respect of each said sample signal:
_~ , using a first algorithm to calculate a first expected value of said sample signal, said first algorithm using actual values of adjacent sample signals in the sarne horizontal line as said sample signal for said calculation;
2û performing a first comparison between said first expected value and the actual value of said sample signal;
using a second algorithm to calculate a second expected value of said sample signal, said second algorithm using actual values of adjacent sample signals in the same horizontal line as said sample signal and actual values of 25 adjacent sample signals in the horizontal lines preceding and following the horizontal line of said sample signal;
performing a second comparison between said second expected value and the actual value of said sample signal;
continuously storing an indication as to which of said ~irst and second 30 cornparisons gives the closer result; and ~p l on occurrence of an error sample signal substituting a corrected sample signal for said error sample signal so as to conceal the error, said corrected sample signal being generaled using said first or second algorithm in dependence on said indication.
According to the present invention there is also provided apparatus for concealing errors in a composite PAL or NTSC digital television signal, which te!evision signal comprises a plurality of sample signals corresponding _ respectively to sample positions along a horizontal scan line of a television picture made up of a plurality of such lines, the apparatus comprising:
means operative in respect of each said sample signal to use a first algorithm to calculate a first expected value of said sarople signal, said firstalgorithm using actual values of adjacent sample signals in the same ~" .
horizontal line as said sample signal for said calculation;
means for performing a first comparison between said first expected value 15 and the actual value of said sample signal;
means operative in respect of each said sample value to use a second algorlthm to calculate a second expected value of said sample signal, said second algorithm using actual values of adjacent sample signals in the same horizontal line as said sample signal and actual values of adjacent sample 20 signals in the horizontal lines preceding and following the horizontal line of said sample signal;
. means for perforrning a second comparison between said second expected -~
value and the actual value of said sample signal;
means for continuously storing an indlcation as to which of said first and 25 second comparisons gives the closer result; and means operative on occurrence of an error sarnple signal to substitute a _ corrected sample signal for said error sample signal so as to corlceal the error, said corrected sample signal being generated using said first or second .
algorithm in dependence on said indication.
The above, and other objects, features and advantages of the invention will be apparent from the following detailed description of illus~rative embodirnents which is to be read in connection with the accompanying drawings.
BRlEF DESCRIPTlON OFTHE DRAWINGS
Figures 1 to 4 show respective parts of a matrix of sample positions ¦ in one field of a composite PAL digital television signal;
Figure 5 shows in block form an embodiment of apparatus for concealing errors in a composite PAL or NTSC digital television signal and 10 according to the invention; and Figures 6 and 7 show respective parts of a matrix of sample positions in one field of a composite NTSC digital television signal.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The m0thod and apparatus to be described are for error concealment 15 in a composite PAL or NTSC digital television signal. Consideration will first be given to a PAL signal~ and the modifications for an NTSC signal will then be considered. The sarnpling frequency used to sarnple the analog PAL
television signal is approximately 8.B Megahertz, and as this is twice th color sub-carrier frequency of the television signal the resulting data is 20 sometimes referred to as 2fSC data. At this sampling frequency the Nyquist frequency is approximately 4.4 Megahertz which is below the maximum frequency of 5.5 Megahertz to be sampled, so the system is sub-Nyquist and in theory frequencies above approximately 4.4 Megahertz cannot be reproduced. In practice, however, by use of suitable two-dimension filtering 25 higher frequencies can be reproduced. This is explained in more detail in :
IBA Technical Review, No.12~ pp 3 to 1~.
_ i Referring to Figure 1 this shows part of a matrix of sample positions in one field of a television picture, four consecutive horizontal scan lines of the picture being shown. The sample positions are disposed at regular 3û intervals along each of the lines, the intervals corresponding to the sampling . I
frequency of approximately 8.8 Megahertz, and the sample positions in alternate lines are aligned in the vertical direction. In adjacent lines the sample positions are off-set by half the interval, so that viewed in the -vertical direction the sarnple positions in one line ~all mid-way between the 5 sample positions in the lines immediately above and below. Thus the overall pattern is diagonal rather than orthogonal.
Moreover, if the chrominance component of each sample is taken as __ C9 then the actual samples alternate c, -c, c, -c, ...... in say even-numbered lines. In the odd-numbered lines also the samples alternate in sign, and are 10 in fact jc, -jc, jc, -jc, ... For convenience, and for ready comparison with the NTSC sample matrices described below, the samples are designated cn, ~cr~, ... cn+1, -cn+1, ... etc., the suffices corresponding to the line numbers, in Figures 1, 3 and 4. Due to the PAL quarter-line off-set the positive and negative samples in the even-numbered lines and in the odd-numbered lines - 15 also alternate in the vertical direction, so the pattern ir dicated in Figure 1 .~' .;: repeats at four line intervals. The PAL 25 Hertz off-set results in only a , . j .
_~ ; srnall error in embodiments of the invention and will therefore be ignored.
Reading from the top, consecutive lines are denoted n-2, n-1, n, n~1, ..., and reading from the left consecutive sample positions in the odd-20 numbered lines are denoted.. S-2, S-1, S, S+1, 5+2, .. ...and in the odd-numbered lines are denotedS-22, S-1~, S-~, S+~, 5+12, 5+2~, Using this notation~ any sample position in the matrix can be designated by the line and sample number, so sample ,oosition n, S is in line n at position S.
.~ The concealment method operates using two algorithms each of 25 which is used oontinuously to calculate expected sample values at each sample position from the known sample values at near-by sample positions.
_ Each expected value is then compared with the actual sample value at that position and an indication of which algorithm is producing expected values closer to the actual values at any time is stored. Then, on occurrence of an 30 error sarnple, the algorithm currently giving the closer values is used to fi ~3~,~ ! ~7~
.
calculate a corrected sample value which is thel~ substituted in place of the error sample.
The ~act that there is an error at a given sample posil ion can be determined in any suitable manner, and the manner used is not oF critical 5importance to the concealment method nuw being described. Briefly, however, and purely by way of example, it may be determined that the data ¦ word representing the sample value is not valid. As a more specific __ example, suppose that each sample value is coded into a word in the sub-set of 10-bit words which consist of 5 "0" and 5 "1"; this being convenient for L lomagnetic recording and reproduction because of the large number of transients and the ease of clock recovery. In this case any reproduced data word not having 5 "û" and 5 "1" is not a valid member of the sub-set and so is clearly an error. Thereupon a flag signal indicating an error sample is generated.
15The two algorithms used will now be described, and they will be designated as algorithms A1 and A2.
The first algorithm A1 uses a simple averaging technique whereby the expected sample value at a given sample position is calculated by averaging the actual sample values at the next-but-one sample positions before and 20after the given sample position in the same horizontal line. The next-but-- one sample positions are used, rather than the imrnediately adjacant ones partly to reduce the chance of the sample values used for the algorithm also - themselves being in error, but also to avoid problems resulting from the . alternating signs of the chrominance component.
25If then AlV is an expected sample value calculated using the algorithm A1 and AV is an actual sample value, then the algorithm A1 may be represented as:
AlV(n, S) = 1 AV(n, S-2) + 2 AV(n, S~2) This is also illustrated in Figure 2 from which it will be seen that the algorithm A1 will continue to produce appropriate expected sample values as the sample position for which the calculation is being per~ormed steps _ ~
along the horizontal line n. Reference to Figure 3 will show that this is also 5 true of the odd-numbered lines. In other words the algorithm Al is independent of the values of n and S.
. ~ . i The algorithm A1 has very good vertical resolution9 but the _ I horizontal resolution is relatively poor and indeed it can be shown that there are circumstances where concealrnent based exclusively on the algorithm A1 10 produces worse results in a television picture than no concealment at all.
It will be noted that the algorithm A1 is a one-dimensional algorithm, . . .
as it uses sample values from a single horizontal line. The algorithm A2, on the other handl uses sample values from three consecutive horizontal lines and has good horizontal resolution. The sample values used are those at the 15 eight sample positions nearest to the given sample position and a summation is used which takes into account the signs of the sample values. ~ing the --~ same notation as before, the algorithm A2 may be represented as:
A2V(n, S) = 3- AV(n-1, 5~ 2) ~ 8 AV(n-1, 5+ 12) + B AV(n, S-2) - 3 AV(n, S-1) .
~.., . ~
3 AV(n, S+1) + 18 AV(n, S+2) . ... -j .
~'-+ 3 AV(n~1, S- 2) + 3 AV(n+1, 5+ 2) : .
--l This is also illustrated in Figure 4 from which it will be seen that in the particular example shown therein, and due to the signs of the sample values . .
and the signs used in the algorithm A2, the algorithm A2 sums to "cn".
30 Likewise when the next sample position S+1 to the right in the same 32Z~:~
horizontal line n is considered, it sums to "-cn". Likewise for the sarnple position n+l, S+ 2J for example, it sums to "cn+l'l as required. In other words the algorithm A2 is also independent of the values of n and S.
Although in describing the algorithms Al and A2 particular consideration has been given to the chrominancf~ components, it will be apparent from the fact that in both the algorithms Al and A2 the - ¦ coefficients sum to unity, that they are also appropriate for luminance _ components. Thus for a flat grey field, for example, it will be seen that the algorithms Al and A2 will give correct values for AlV and A2V respectively.
Referring to Figure 5, this shows apparatus for concealing errors in a PAL digital television signal. The apparatus comprises a sample storage rneans 1 to which input samples which may, for example, have been reproduced from a digital VTR are supplied by way of an input terrninal 2.
The sample storage means 1 supplies outputs to a sample matrix storage means 3 which stores a moving matrix of sample values corresponding to the sample positions n-l, 5~ 2; n-l, 5~ 1; n, 5-2; n, S-l; n, 5; n, 5~1; n, 5+2; n~l, ' S- 2; and n+l3 5+ 2 Part of the output of the sample matrix storage means 3 is supplied to an Al algorithm calculation circuit 4 which for each sample position calculates the expected sample value AlV and supplies it to a comparison circuit 4 where it is compared with the actual value AV. This comparison results in an error signal, the magnitude of which represents the error i ~. ., between the estimated sample value AlV and the actual sample valuP AV7 this error signal being supplied to an algorithm selection circuit 6.
The output of the sample matrix storage n~eans 3 is supplied to an A2 ~ algorithm calculation circuit 7 whicl for each sample position calculàtes the - expected sample value A2V and supplies it to a cDmparison circuit 8 where it is compared with the actual sample value AV. This comparison results in a further error signal, the magnitude of which represents the error between the estimated sample value A2V and the actual sample value AV, this further error signal also ~eing supplied to the algorithm selection circuit 6.
On the basis of the rnagnitudes of the error signals supplied to it, the algorithm selection circuit 6 selects the alyorithm A1 or A2 which at that _ ~
given moment is resulting in more accurate estirnated sample values, and an 5 indication of the algorithm A1 or A2 so selected is stored in a storage means . 9.
The indication stored in the storage means 9 is supplied to a sample value calculator 10 to which the output of the sample matrix storage means 3 is also supplied, the sample value calculator 10 calculating an estimated 10 sample value A1V or A2V in dependence on the algorithm A1 or A2 currently .
indicated in the storage means 9. This estimated sample value AlV or A2V
is supplied to a switching circuit 11. The input samples supplied to the input terminal 2 are also supplied by way of timing circuits 12 to the switching circuit 11.
Normally, the input samples supplied from the input terminal 2 by way of the timing circuits 12 will be supplied by the switching circuit 11 to an output terminal 13 Howevsr, on the occurrence of an error an error flag signal is supplied to a terminal 14 connected to the switching circuit 11 and causes the switching circuit 11 to switch so as to substitute the estimated 20 sample value A1V or A2V for the error sample value in the sample values supplied to the output terminal 13.
Various refinements and extensions of the method and apparatus are of course possible. For example, in the above description it has been - ~-- assumed that the algorithm A1 or A2 is selected by a simple comparison of 25 the accuracy of the estimated sample values A1V and A2V with the actual .r''~ sample value AV. In certain circumstances, however, it may be expected that one or other of the algorithms A1 or A2 will give a more accurate result, and in this case rather than a simple comparison, some weighting of one or other of the algorithms A1 or A2 may be introduced.
It will be understood that the timing circuits 12 operate so that the estimated sarnple value A1V or A2V which is used will normally be one based on the last available sample values prior to the sample yalue which is in error. Howe~er, at any given time at least one complele field of sample values is available for signal processing, and it is not therefore essential to use an estimated sample value AlV or A2V based on actual sarnple values preceding the sample value which is in error, as an estimated sample value AlV or A2V based on actual sample values subsequent to the error sample _ value may alternatively, or in additinn, be used.
The modifications necessary in the case of a composite NTSC digital 10 television signal will now be cor sidered. The sampling frequency used to sample the analog NTSC television siynal is approximately 7.2 Megahertz, the actual frequency being twice the color sub-carrier frequency f'sc of the television signal, minus or plus one quarter of the line scan frequency fH.
At this sampling frequency the Nyquist frequency is approximately 15 3.6 Megahertz which is below the maximum frequency of 4.5 Megahertz to - be sampled, so again the system is sub-Nyquist and in theory frequencies above 3.6 Megahertz cannot be reproduced. This is explained in more detail in SMPTE Journal, January 1976~ in an article "Sub-Nyquist encoding of PCM NTSC color television" by John Rossi.
Referring to Figures 6A and 6B, these show parts of matrices of sample positions in one field of a television picture, five consecutive horizontal scan lines of the picture being shown, for sampling freque~ecies of f'SC-2;fH and f'Sc+~fH respectively. The sample positions are disposed at regular intervals along each of the lines, the intervals corresponding to the 25 sampling frequency of approximately 7.2 Megahertz, and the sample _ positions in every fourth line are aligned in the vertical direction. In adjacent lines the sample positions are off-set by one quarter of the interval. Thus again the overall pattern is diagonal rather than orthogonal.
Moreover, as with a PAL signal, if the chrorninance component of 30 each sample is taken as c, then the actual samples alternate c, -c, c~ -c, .~
in say even-numbered lines. In the line n, for example, the samples are designated c7n, ~c'n, c'n, -c'n, ... In odd-numbered lines the samples again alternate in sign and are designated c n-1~ c n-1~ -- c n*1~ n+1~
-- with the PAL sample matrix, the pattern repeats at four line intervals.
Reading from the top, consecutive lines are again denoted n-2, n-1, n, n+1, ..., and reading from the left consecutive sarnple positions in the line n are denoted ... S-2, S-1, S, 5+1, 5+2, ..., and sirnilarly for the other lines as indicated, having in mind that in this case the off-set between adjacent lines is one quarter.
As for a PAL signal, two algorithms are used, and the first is the algorithm A1 described above.
The second algorithm takes one of two forms depending on the sampling frequency. For the sampling frequencies f'Sc-~fH and f'sc+-~f the second algorithm is designated A'2 and A"2 respectively. In both cases _ 15 the sample values used are those at eight near-by sample positions and a ; summation is used which takes into account the signs of the sample values.
.~ I Using the same notation as before, the algorithm A'2 may be represented as:
A'2V(n, S) = 3 AV(n-1, S- 3) -~ 3 AV(n-l, S+ 1~) + 18 AV(n,~S-2) 3 AV(n, S-1) .
- 3 AV(n, 5+1) f 8 AV(n, S+2) .. . .. .
25+ 3 AV(n+17 S- 4) + 3 AV(n+1, S+ 3) _ l This is also illustrated in Figure 7A, while Figure 7B illustrates the algorithm A"2, which may be represented as:
30A"2V(n, S) = 3 AV(n-1, 5~ 4) + 8 AV(n-1, S+ 3) ~ P ~ 229Çci + 8 AV(n, 5-2) - 3 AV(n, S-1) - 3 AV(n, 5+1) ~ 8 AV(n, S~2) ~ 8 AV(n+1, S- 4) + 3 AV(n~1, S+ 1) .
It will be apparent that the apparatus of Figure 5 requires modification for an NTSC digital te!evision signal. In particular, the moving matrix of sample values supplied by the sample storage means 1 is 10 appropriately modified, and the algorithm calculation circuit 7 calculates the algorithm A'2 or A"2 as appropriate.
The invention is not limited to concealment of errors which have arisen in the course of recording and reproducing from a VTF;!, but may be used in any situation where errors have arisen in processing, transmitting or 15 handling a composite PAL or NTSC digital television signal.
- - Although illustrative embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications can be effected 20 therein by one skilled in the art without department from the scope and spirit of the invention as defined by the appended claims.
. . I , ..;,
Claims (7)
1. A method of concealing errors in a composite PAL or NTSC digital television signal, which television signal comprises a plurality of sample signals corresponding respectively to sample positions along a horizontal scan line of a television picture made up of a plurality of said horizontal lines, the method comprising, in respect of each said sample signal:
using a first algorithm to calculate a first expected value of said sample signal, said first algorithm using actual values of adjacent sample signals in the same horizontal line as said sample signal for said calculation;
performing a first comparison between said first expected value and the actual value of said sample signal;
using a second algorithm to calculate a second expected value of said sample signal, said second algorithm using actual values of adjacent sample signals in the same horizontal line as said sample signal and actual values of adjacent sample signals in the horizontal lines preceding and following the horizontal line of said sample signal;
performing a second comparison between said second expected value and the actual value of said sample signal;
continuously storing an indication as to which of said first and second comparisons gives the closer result; and on occurrence of an error sample signal substituting a corrected sample signal for said error sample signal so as to conceal the error, said corrected sample signal being generated using said first or second algorithm in dependence on said indication.
using a first algorithm to calculate a first expected value of said sample signal, said first algorithm using actual values of adjacent sample signals in the same horizontal line as said sample signal for said calculation;
performing a first comparison between said first expected value and the actual value of said sample signal;
using a second algorithm to calculate a second expected value of said sample signal, said second algorithm using actual values of adjacent sample signals in the same horizontal line as said sample signal and actual values of adjacent sample signals in the horizontal lines preceding and following the horizontal line of said sample signal;
performing a second comparison between said second expected value and the actual value of said sample signal;
continuously storing an indication as to which of said first and second comparisons gives the closer result; and on occurrence of an error sample signal substituting a corrected sample signal for said error sample signal so as to conceal the error, said corrected sample signal being generated using said first or second algorithm in dependence on said indication.
2. A method according to claim 1 wherein said first algorithm is represented as:
AlV(n,S) = where AlV(n, S) is said estimated sample value for the sample position S in the horizontal line n calculated using said first algorithm, and AV(n,S) is said actual value for the sample position S in the horizontal line n.
AlV(n,S) = where AlV(n, S) is said estimated sample value for the sample position S in the horizontal line n calculated using said first algorithm, and AV(n,S) is said actual value for the sample position S in the horizontal line n.
3. A method according to claim 2 wherein said second algorithm uses actual values of four sample signals adjacent to said sample signal in the same horizontal line as said sample signal and actual values of two sample signals adjacent to said sample signal in each of the horizontal lines immediately preceding and succeeding the horizontal line of said sample signal.
4. A method according to claim 2 wherein said television signal is a PAL
signal, and wherein said second algorithm is represented as:
A2V(n,S) = where A2V(n, S) is said estimated sample value for the sample position S in the horizontal line n calculated using said second algorithm, and AV(n, S) is said actual value for the sample position S in the horizontal line n.
signal, and wherein said second algorithm is represented as:
A2V(n,S) = where A2V(n, S) is said estimated sample value for the sample position S in the horizontal line n calculated using said second algorithm, and AV(n, S) is said actual value for the sample position S in the horizontal line n.
5. A method according to claim 2 wherein said television signal is an NTSC signal, and wherein said second algorithm is represented as:
A'2V(n,S) = where A'2V(n,S) is said estimated sample value for the sample position S in the horizontal line n calculated using said second algorithm, and AV(n,S) is said actual value for the sample position S in the horizontal line n.
A'2V(n,S) = where A'2V(n,S) is said estimated sample value for the sample position S in the horizontal line n calculated using said second algorithm, and AV(n,S) is said actual value for the sample position S in the horizontal line n.
6. A method according to claim 2 wherein said television signal is an NTSC signal, and wherein said second algorithm is represented as:
A"2V(n,S) = where A"2V(n,S) is said estimated sample value for the sample position S in the horizontal line n calculated using said second algorithm, and AV(n,S) is said actual value for the sample position S in the horizontal line n.
A"2V(n,S) = where A"2V(n,S) is said estimated sample value for the sample position S in the horizontal line n calculated using said second algorithm, and AV(n,S) is said actual value for the sample position S in the horizontal line n.
7. Apparatus for concealing errors in a composite PAL or NTSC digital television signal, which television signal comprises a plurality of sample signals corresponding respectively to sample positions along a horizontal scan line of a television picture made up of a plurality of said horizontal lines, the apparatus comprising:
means operative in respect of each said sample signal to use a first algorithm to calculate a first expected value of said sample signal, said first algorithm using actual values of adjacent sample signals in the same horizontal line as said sample signal for said calculation;
means for performing a first comparison between said first expected value and the actual value of said sample signal;
means operative in respect of each said sample value to use a second algorithm to calculate a second expected value of said sample signal, said second algorithm using actual values of adjacent sample signals in the same horizontal line as said sample signal and actual values of adjacent sample signals in the horizontal lines preceding and following the horizontal line of said sample signal;
means for performing a second comparison between said second expected value and the actual value of said sample signal;
means for continuously storing an indication as to which of said first and second comparisons gives the closer result; and means operative on occurrence of an error sample signal to substitute said corrected sample signal for said error sample signal so as to conceal the error, said said corrected sample signal being generated using said first or second algorithm in dependence on said indication.
means operative in respect of each said sample signal to use a first algorithm to calculate a first expected value of said sample signal, said first algorithm using actual values of adjacent sample signals in the same horizontal line as said sample signal for said calculation;
means for performing a first comparison between said first expected value and the actual value of said sample signal;
means operative in respect of each said sample value to use a second algorithm to calculate a second expected value of said sample signal, said second algorithm using actual values of adjacent sample signals in the same horizontal line as said sample signal and actual values of adjacent sample signals in the horizontal lines preceding and following the horizontal line of said sample signal;
means for performing a second comparison between said second expected value and the actual value of said sample signal;
means for continuously storing an indication as to which of said first and second comparisons gives the closer result; and means operative on occurrence of an error sample signal to substitute said corrected sample signal for said error sample signal so as to conceal the error, said said corrected sample signal being generated using said first or second algorithm in dependence on said indication.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8030149 | 1980-09-18 | ||
| GB8030149A GB2084432A (en) | 1980-09-18 | 1980-09-18 | Error concealment in digital television signals |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1162296A true CA1162296A (en) | 1984-02-14 |
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ID=10516140
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000386031A Expired CA1162296A (en) | 1980-09-18 | 1981-09-16 | Error concealment in digital television signals |
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| US (1) | US4381519A (en) |
| EP (1) | EP0048569B1 (en) |
| JP (1) | JPS5781787A (en) |
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| CA (1) | CA1162296A (en) |
| DE (1) | DE3169059D1 (en) |
| GB (1) | GB2084432A (en) |
Families Citing this family (94)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0799804B2 (en) * | 1981-07-13 | 1995-10-25 | ソニー株式会社 | Filter device |
| US4470065A (en) * | 1982-03-25 | 1984-09-04 | Rca Corporation | Adaptive error concealment using horizontal information determination from adjacent lines |
| GB2120494B (en) * | 1982-05-14 | 1985-10-16 | Sony Corp | Error concealment in digital television signals |
| US4517600A (en) * | 1982-05-17 | 1985-05-14 | Rca Corporation | Error concealment system using dropout severity information for selection of concealment method |
| GB2121642B (en) * | 1982-05-26 | 1985-11-27 | Sony Corp | Error concealment in digital television signals |
| JPS5978350A (en) * | 1982-10-27 | 1984-05-07 | Dainippon Printing Co Ltd | Plate making system for video picture |
| JPS5978348A (en) * | 1982-10-27 | 1984-05-07 | Dainippon Printing Co Ltd | Plate making system for video picture |
| JPS5978349A (en) * | 1982-10-27 | 1984-05-07 | Dainippon Printing Co Ltd | Plate making system for video picture |
| JPS5978347A (en) * | 1982-10-27 | 1984-05-07 | Dainippon Printing Co Ltd | Plate making system for video picture |
| JPS5978352A (en) * | 1982-10-28 | 1984-05-07 | Dainippon Printing Co Ltd | Plate making system for video picture |
| JPS5978351A (en) * | 1982-10-28 | 1984-05-07 | Dainippon Printing Co Ltd | Plate making system for video picture |
| JPS60180A (en) * | 1983-06-15 | 1985-01-05 | Victor Co Of Japan Ltd | Video signal recording and reproducing device |
| JPS6139783A (en) * | 1984-07-31 | 1986-02-25 | Matsushita Electric Ind Co Ltd | Recording and reproducing device |
| GB2164521B (en) * | 1984-09-18 | 1988-02-03 | Sony Corp | Error concealment in digital television signals |
| US4706113A (en) * | 1985-02-18 | 1987-11-10 | Mitsubishi Denki Kabushiki Kaisha | Contour detecting filter device using PAL samples of composite video signals without separation of luminance signals therefrom |
| JPH06105986B2 (en) * | 1985-04-19 | 1994-12-21 | ソニー株式会社 | Error correction method for image data |
| US4760470A (en) * | 1985-09-27 | 1988-07-26 | Ampex Corporation | Multi-standard adaptive dropout compensator |
| GB8526817D0 (en) * | 1985-10-31 | 1985-12-04 | Crosfield Electronics Ltd | Image enhancement |
| DE3719405C2 (en) * | 1987-06-11 | 1994-09-29 | Broadcast Television Syst | Circuit arrangement for concealing errors |
| JPH02184192A (en) * | 1989-01-11 | 1990-07-18 | Matsushita Electric Ind Co Ltd | Error correction device for pal color video signal |
| US5231680A (en) * | 1990-12-21 | 1993-07-27 | Ampex Systems Corporation | Horizontal adaptive error concealment system for component digital television signals |
| EP0744869B1 (en) * | 1990-12-28 | 2000-03-22 | Canon Kabushiki Kaisha | Image processing apparatus |
| US6469741B2 (en) | 1993-07-26 | 2002-10-22 | Pixel Instruments Corp. | Apparatus and method for processing television signals |
| US6298085B1 (en) | 1997-10-23 | 2001-10-02 | Sony Corporation | Source encoding using shuffling of data to provide robust error recovery in a burst error-environment |
| US6581170B1 (en) | 1997-10-23 | 2003-06-17 | Sony Corporation | Source coding to provide for robust error recovery during transmission losses |
| US6282684B1 (en) | 1997-10-23 | 2001-08-28 | Sony Corporation | Apparatus and method for recovery of data in a lossy transmission environment |
| US6535148B1 (en) | 1999-02-12 | 2003-03-18 | Sony Corporation | Method and apparatus for truncated decoding |
| US7010737B2 (en) * | 1999-02-12 | 2006-03-07 | Sony Corporation | Method and apparatus for error data recovery |
| US6178266B1 (en) | 1999-02-12 | 2001-01-23 | Sony Corporation | Method and apparatus for the recovery of compression constants in the encoded domain |
| US6363118B1 (en) | 1999-02-12 | 2002-03-26 | Sony Corporation | Apparatus and method for the recovery of compression constants in the encoded domain |
| US6519369B1 (en) | 1999-02-12 | 2003-02-11 | Sony Corporation | Method and apparatus for filter tap expansion |
| US6307979B1 (en) | 1999-02-12 | 2001-10-23 | Sony Corporation | Classified adaptive error recovery method and apparatus |
| US6307560B1 (en) | 1999-02-12 | 2001-10-23 | Sony Corporation | Classified adaptive spatio-temporal format conversion method and apparatus |
| US6192161B1 (en) | 1999-02-12 | 2001-02-20 | Sony Corporation | Method and apparatus for adaptive filter tap selection according to a class |
| US6151416A (en) * | 1999-02-12 | 2000-11-21 | Sony Corporation | Method and apparatus for adaptive class tap selection according to multiple classification |
| US6170074B1 (en) | 1999-02-12 | 2001-01-02 | Sony Corporation | Source coding to provide for robust error recovery |
| US6154761A (en) * | 1999-02-12 | 2000-11-28 | Sony Corporation | Classified adaptive multiple processing system |
| US6591398B1 (en) | 1999-02-12 | 2003-07-08 | Sony Corporation | Multiple processing system |
| US6621936B1 (en) | 1999-02-12 | 2003-09-16 | Sony Corporation | Method and apparatus for spatial class reduction |
| US6697489B1 (en) | 1999-03-30 | 2004-02-24 | Sony Corporation | Method and apparatus for securing control words |
| US7565546B2 (en) | 1999-03-30 | 2009-07-21 | Sony Corporation | System, method and apparatus for secure digital content transmission |
| US7730300B2 (en) * | 1999-03-30 | 2010-06-01 | Sony Corporation | Method and apparatus for protecting the transfer of data |
| US6389562B1 (en) | 1999-06-29 | 2002-05-14 | Sony Corporation | Source code shuffling to provide for robust error recovery |
| US6549672B1 (en) | 1999-06-29 | 2003-04-15 | Sony Corporation | Method and apparatus for recovery of encoded data using central value |
| US6473876B1 (en) | 1999-06-29 | 2002-10-29 | Sony Corporation | Method and apparatus for encoding of bitstreams using rotation |
| US6493842B1 (en) | 1999-06-29 | 2002-12-10 | Sony Corporation | Time-varying randomization for data synchronization and implicit information transmission |
| US6351494B1 (en) | 1999-09-24 | 2002-02-26 | Sony Corporation | Classified adaptive error recovery method and apparatus |
| US6522785B1 (en) | 1999-09-24 | 2003-02-18 | Sony Corporation | Classified adaptive error recovery method and apparatus |
| US7039614B1 (en) * | 1999-11-09 | 2006-05-02 | Sony Corporation | Method for simulcrypting scrambled data to a plurality of conditional access devices |
| US6539517B1 (en) | 1999-11-09 | 2003-03-25 | Sony Corporation | Data transformation for explicit transmission of control information |
| US6754371B1 (en) | 1999-12-07 | 2004-06-22 | Sony Corporation | Method and apparatus for past and future motion classification |
| US7225164B1 (en) * | 2000-02-15 | 2007-05-29 | Sony Corporation | Method and apparatus for implementing revocation in broadcast networks |
| US20040205812A1 (en) * | 2000-06-22 | 2004-10-14 | Candelore Brant L. | Method and apparatus for routing program data in a program viewing unit |
| US20030206631A1 (en) * | 2000-06-22 | 2003-11-06 | Candelore Brant L. | Method and apparatus for scrambling program data for furture viewing |
| US7350082B2 (en) * | 2001-06-06 | 2008-03-25 | Sony Corporation | Upgrading of encryption |
| US7747853B2 (en) | 2001-06-06 | 2010-06-29 | Sony Corporation | IP delivery of secure digital content |
| US7895616B2 (en) | 2001-06-06 | 2011-02-22 | Sony Corporation | Reconstitution of program streams split across multiple packet identifiers |
| US7127619B2 (en) | 2001-06-06 | 2006-10-24 | Sony Corporation | Decoding and decryption of partially encrypted information |
| US7292691B2 (en) | 2002-01-02 | 2007-11-06 | Sony Corporation | Progressive video refresh slice detection |
| US7302059B2 (en) * | 2002-01-02 | 2007-11-27 | Sony Corporation | Star pattern partial encryption |
| US7215770B2 (en) * | 2002-01-02 | 2007-05-08 | Sony Corporation | System and method for partially encrypted multimedia stream |
| US7039938B2 (en) * | 2002-01-02 | 2006-05-02 | Sony Corporation | Selective encryption for video on demand |
| US7376233B2 (en) * | 2002-01-02 | 2008-05-20 | Sony Corporation | Video slice and active region based multiple partial encryption |
| US7242773B2 (en) * | 2002-09-09 | 2007-07-10 | Sony Corporation | Multiple partial encryption using retuning |
| US7765567B2 (en) | 2002-01-02 | 2010-07-27 | Sony Corporation | Content replacement by PID mapping |
| US7233669B2 (en) * | 2002-01-02 | 2007-06-19 | Sony Corporation | Selective encryption to enable multiple decryption keys |
| US7155012B2 (en) * | 2002-01-02 | 2006-12-26 | Sony Corporation | Slice mask and moat pattern partial encryption |
| US7218738B2 (en) * | 2002-01-02 | 2007-05-15 | Sony Corporation | Encryption and content control in a digital broadcast system |
| US7823174B2 (en) | 2002-01-02 | 2010-10-26 | Sony Corporation | Macro-block based content replacement by PID mapping |
| US20090180025A1 (en) * | 2002-05-28 | 2009-07-16 | Sony Corporation | Method and apparatus for overlaying graphics on video |
| US7530084B2 (en) * | 2002-05-28 | 2009-05-05 | Sony Corporation | Method and apparatus for synchronizing dynamic graphics |
| US8818896B2 (en) | 2002-09-09 | 2014-08-26 | Sony Corporation | Selective encryption with coverage encryption |
| US7724907B2 (en) | 2002-11-05 | 2010-05-25 | Sony Corporation | Mechanism for protecting the transfer of digital content |
| US8572408B2 (en) | 2002-11-05 | 2013-10-29 | Sony Corporation | Digital rights management of a digital device |
| US8645988B2 (en) * | 2002-12-13 | 2014-02-04 | Sony Corporation | Content personalization for digital content |
| US8667525B2 (en) * | 2002-12-13 | 2014-03-04 | Sony Corporation | Targeted advertisement selection from a digital stream |
| US20040165586A1 (en) * | 2003-02-24 | 2004-08-26 | Read Christopher Jensen | PID filters based network routing |
| US7409702B2 (en) * | 2003-03-20 | 2008-08-05 | Sony Corporation | Auxiliary program association table |
| US7292692B2 (en) | 2003-03-25 | 2007-11-06 | Sony Corporation | Content scrambling with minimal impact on legacy devices |
| US20050036067A1 (en) * | 2003-08-05 | 2005-02-17 | Ryal Kim Annon | Variable perspective view of video images |
| US7286667B1 (en) | 2003-09-15 | 2007-10-23 | Sony Corporation | Decryption system |
| US20050066357A1 (en) * | 2003-09-22 | 2005-03-24 | Ryal Kim Annon | Modifying content rating |
| US20050097597A1 (en) * | 2003-10-31 | 2005-05-05 | Pedlow Leo M.Jr. | Hybrid storage of video on demand content |
| US20050097596A1 (en) * | 2003-10-31 | 2005-05-05 | Pedlow Leo M.Jr. | Re-encrypted delivery of video-on-demand content |
| US7853980B2 (en) * | 2003-10-31 | 2010-12-14 | Sony Corporation | Bi-directional indices for trick mode video-on-demand |
| US7263187B2 (en) * | 2003-10-31 | 2007-08-28 | Sony Corporation | Batch mode session-based encryption of video on demand content |
| US7343013B2 (en) * | 2003-12-16 | 2008-03-11 | Sony Corporation | Composite session-based encryption of video on demand content |
| US7620180B2 (en) * | 2003-11-03 | 2009-11-17 | Sony Corporation | Preparation of content for multiple conditional access methods in video on demand |
| US7346163B2 (en) * | 2003-10-31 | 2008-03-18 | Sony Corporation | Dynamic composition of pre-encrypted video on demand content |
| US20050102702A1 (en) * | 2003-11-12 | 2005-05-12 | Candelore Brant L. | Cablecard with content manipulation |
| US7895617B2 (en) | 2004-12-15 | 2011-02-22 | Sony Corporation | Content substitution editor |
| US8041190B2 (en) | 2004-12-15 | 2011-10-18 | Sony Corporation | System and method for the creation, synchronization and delivery of alternate content |
| US8185921B2 (en) | 2006-02-28 | 2012-05-22 | Sony Corporation | Parental control of displayed content using closed captioning |
| US7555464B2 (en) * | 2006-03-01 | 2009-06-30 | Sony Corporation | Multiple DRM management |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3009016A (en) * | 1959-10-06 | 1961-11-14 | Bell Telephone Labor Inc | Noise suppressing video circuit |
| FR2320017A1 (en) * | 1975-07-29 | 1977-02-25 | Telecommunications Sa | Reduction of information for image coding - uses transmission of every other point with correlation bit describing untransmitted point |
| JPS5851472B2 (en) * | 1976-02-25 | 1983-11-16 | ケイディディ株式会社 | Line-to-line predictive coding method for television signals |
| JPS52102617A (en) * | 1976-02-25 | 1977-08-29 | Kokusai Denshin Denwa Co Ltd | Television signal predictive coding system between two lines |
| JPS52122041A (en) * | 1976-04-06 | 1977-10-13 | Nippon Telegr & Teleph Corp <Ntt> | Color video signal predictive coding |
| FR2359559A1 (en) * | 1976-07-23 | 1978-02-17 | Thomson Csf | Video drop out compensator - compares delayed and undelayed signals and corrects lost picture elements by interpolation |
| US4141035A (en) * | 1977-10-20 | 1979-02-20 | Bell Telephone Laboratories, Incorporated | Technique for separating composite video signals |
| US4323916A (en) * | 1980-02-07 | 1982-04-06 | Rca Corporation | Data rate reduction for digital video signals by subsampling and adaptive reconstruction |
| GB2069294B (en) * | 1980-02-07 | 1984-09-19 | Rca Corp | Data rate reduction for data transmission or recording |
| GB2070884B (en) * | 1980-02-28 | 1984-08-08 | Rca Corp | Adaptive dropout compensator and estimator therefor |
| GB2073534B (en) * | 1980-04-02 | 1984-04-04 | Sony Corp | Error concealment in digital television signals |
-
1980
- 1980-09-18 GB GB8030149A patent/GB2084432A/en not_active Withdrawn
-
1981
- 1981-09-09 AT AT81304131T patent/ATE11991T1/en not_active IP Right Cessation
- 1981-09-09 EP EP81304131A patent/EP0048569B1/en not_active Expired
- 1981-09-09 DE DE8181304131T patent/DE3169059D1/en not_active Expired
- 1981-09-14 US US06/302,153 patent/US4381519A/en not_active Expired - Lifetime
- 1981-09-16 CA CA000386031A patent/CA1162296A/en not_active Expired
- 1981-09-18 JP JP56147341A patent/JPS5781787A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| EP0048569B1 (en) | 1985-02-20 |
| EP0048569A3 (en) | 1982-08-11 |
| JPH0347637B2 (en) | 1991-07-19 |
| JPS5781787A (en) | 1982-05-21 |
| US4381519A (en) | 1983-04-26 |
| EP0048569A2 (en) | 1982-03-31 |
| ATE11991T1 (en) | 1985-03-15 |
| DE3169059D1 (en) | 1985-03-28 |
| GB2084432A (en) | 1982-04-07 |
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