GB2080993A

GB2080993A - Movement Detection Circuit

Info

Publication number: GB2080993A
Application number: GB8122941A
Authority: GB
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1980-07-28
Filing date: 1981-07-24
Publication date: 1982-02-10
Also published as: FR2487617A1; NL8004312A; DE3126713C2; JPS5753190A; DE3126713A1; FR2487617B1; GB2080993B; JPH0331037B2

Abstract

In a movement detection circuit for an interlaced television signal to be applied to an input (3), a delay circuit (5) of substantially one field period feeds delayed and undelayed signals to a comparison circuit (15) which in turn feeds an output circuit (42), a sign reversal detection circuit (126) being provided for use in obtaining a movement indication signal at an output (137) of the output circuit (42). By the use of the sign reversal detection circuit (126) the previous need to use a delay circuit providing a delay of a picture period is overcome. <IMAGE>

Description

SPECIFICATION Movement Detection Circuit The invention relates to a movement detection circuit for an interlaced television signal in which in a comparison circuit information from a plurality of consecutive points is compared with the information from a plurality of corresponding sequential lines which information is obtained from the first-mentioned information by means of a delay circuit, this comparison circuit having an output circuit for obtaining a movement indication signal.Revue de Radio-diffusion-t6l6vision, April/May 1978, pages 35-42 discloses a movement detection circuit of the abovementioned type in which the delay circuit having a delay of a picture period and in which the information of some time-sequential lines is compared in the comparison circuit with the information of some corresponding timesequential lines of a previous picture.

The invention has for its purpose to reduce the number of circuit elements.

According to the invention, a movement detection circuit of the type set forth in the preamble is therefore characterised in that the delay circuit provides delay of substantially one field period with the comparison circuit arranged for comparing information from a number of position-sequential picture lines in a given field with picture lines correspondingly positioned in the preceding field, a sign reversal detection circuit being coupled to the output circuit so that the movement indication signal can only be produced when the sign of differences in the compared information between the two fields is reversed.

When a sign reversal detection circuit is used it is sufficient to substitute a picture delay circuit by a field delay circuit, which results in a considerable saving in circuit elements and which can find futhermore advantageous use in those circuits in which a field memory is used, as for example, in interpolation circuits for line number doublers.

The invention will now be further explained by way of example with reference to an embodiment in the accompanying drawing.

In this drawing: Figure 1 illustrates by means of a block schematic circuit diagram a movement detection circuit according to the invention and Figure 2 illustrates schematically the phenomenon utilised in a circuit of the invention.

In Figure 1 an interlaced television signal is applied to an input 3 of a field delay circuit 5. At any desired moment it must be possible to detect whether a displayed object has moved in a picture displayed by means of this television signal.

Figure 2 shows such an object in the form of a white area against a dark background, which area assumes the position I during one field of a picture and the position II during the next field.

The field delay circuit 5 has an output 7 at which the input signal appears undelayed and an output 9 at which the input signal appears delayed for one field period minus half a line period (R < L).

Figure 2 shows in a corner of the displaced object a portion of a number of picture lines of which information B from a line having number n-i according to the position in which it occurs in a picture is produced at the output 7 and information A from a line having number n according to the position in which it occurs in a picture is produced at the output 9 of the delay circuit 5.

The output 7 and 9, respectively of the delay circuit 5 is connected to an input 11 and 13, respectively, of a comparison circuit 15, which comprises three subtracting circuits 1 7, 1 9, 21.

Two inputs of the subtracting circuit 1 7 are connected to the respective inputs 11 and 13 of the comparison circuit 15. The difference A-B of the information from the picture lines n and n--l is produced at an output 23 of the comparison circuit 1 5 connected to the subtracting circuit 1 7.

The subtracting circuit 19 has an input which is connected directly to the input 11 of the comparison circuit 1 5 and an input which is connected to the input 13 via a delay line 25 having a time delay of one line period (L).

Information C from a line shown in Figure 2 having number n-2 according to the position in which it occurs in the picture, is produced on the connection from this delay line 25 to the input of the subtracting circuit 1 9. The difference B--6 of the information from the picture lines n-1 and n-2 is produced at an output 27 of the comparison circuit 1 5 connected to an output of the subtracting circuit 1 9.

The subtracting circuit 21 has an input which is connected to the input 13 via the delay line 25 and a further input which is connected to the input 11 of the comparison circuit 1 5 via a delay line 29 which has a time delay of one line period (L). Via the delay line 29 information D from a line shown in Figure 2 and having number n-3 according to its position in a picture is applied to the relevant input of the subtracting circuit 21.

The difference C-D of the information from the picture lines n-2 and n-3 is produced at an output 31 of the comparison circuit 1 5 connected to an output of the subtracting circuit 21.

The picture lines n and n-2 in Figure 2 occur in the field in which the displayed object assumes the position I and are therefore lines which reproduce the dark background. The picture lines n-1 and n-3 occur in the field in which the displayed object assumes the position II and are therefore lines which are bright in the area of the object.So in two sub-areas 33 and 35 the lines n, n-1, n-2 and n-3 are alternately dark, bright, dark and bright, which is shown in Figure 2 by 0, 1, 0, 1. So the differences A-B, B-C and C-D at the outputs 23,27 and 31 of the comparison circuit are consecutively-i, +1 and and consequently show a polarity or sign reversal in the displaced area both for horizontal and vertical displacements.

The outputs 27 and 31 of the comparison circuit 1 5 are connected to inputs 37, 39 and 41, respectively of an output circuit 42. These inputs 37, 39, 41 are connected to respective inputs 43 and 45, 47 of limiters 49 and 51, 53, and to respective inputs 55 and 57, 59, of multipliers 61 and 63. 65.

A sign signal S[A--B] and S[B-cj, S[C-D], respectively representing the sign of the differences A-B and B-C, C-D, is produced at outputs 67 and 69,71 of the limiters 49 and 51, 53. The sign signals at the outputs 67 and 69, 71 are respectively applied to a further respective input 73 and 75,77 of the multipliers 61,63,65 and to a respective output 79, 81, 83 of the output circuit 42.

As a result thereof the absolute values IA-El and IB-CI, IC-DI, of the respective signals at the inputs 55, and 57, 59 are produced at the respective outputs 85 and 87,89 of the multipliers 61 and 63,65. As will be clear from Figure 2 and from the foregoing, this absolute value has a value differing from zero in the displaced area.

In three threshold circuits 91 and 93,95, respectively, a respective input 97, 99, 101 of which is connected to the associated output 85 and 87, 89 of the multipliers 61 and 63, 65 a check is made as to whether this value differing from zero exceeds a predetermined threshold value which is determined by a threshold value source 109, which is connected to a further input 103 and 105, 107 of each threshold circuit 91 and 93,95.

A respective output 111 and 113,115 of the threshold circuits 91, and 93, 95, is connected to a corresponding input of an AND-gate 117 an output of which is connected to an input of an AND-gate 119.

The AND-gate 117 applies a logic one signal to the ANDgate 11 9 when the three threshold circuits 91.93, 95 have detected that the threshold value has been exceeded, which is the case in signals in the displaced area.

A respective input 121,123 and 125 of a sign reversal detection circuit 126 is connected to the respective output 79, 81 and 83 of the output circuit 42. In the sign reversal detection circuit 126 the input 121 is connected to an input of an exclusive-OR-gate 127, a further input of which is connected to the input 123 and to an input of a further exclusive-OR-gate 129, a further input of which is connected to the input 125. The outputs of the exclusive-0R-gates 127, 129 are connected to corresponding inputs of an ANDgate 131, an output of which is connected to a further input of the AND-gate 119 via an output 133 of the sign reversal detection circuit 126 and an input 135 of the output circuit 42.The output of the AND-gate 11 9 is connected to an output 1 37 of the circuit in which a logic one signal is produced in the region of movement.

The exclusive-OR-gates produce a signal which is logic one if a signal which is logic one is applied to one of their inputs, a logic zero signal being applied to the other input. If the signals at the inputs 121, 123, 125 are respective logic zero, one and zero, as is the case for the displaced area in the situation outlined in Figure 2, then both exclusive-OR-gates 127,129 produce a logic one signal and consequently also the AND-gate 131 and since the AND-gate 11 7 also produces a logic one signal for the displaced area the output 1 37 bf the output circuit becomes logic one for the displaced area causing a movement indication signal to be produced at the output 137.

As this movement indication signal is produced for the displaced area for both horizontal and vertical displacements a separate detection for both directions is not required.

In the embodiment shown the same threshold value is chosen for each threshold circuit 91,93, 95. It will be clear that, if so desired different threshold values may be used.

Although the number of position-sequential picture lines which are checked for movement detection is four in this description, it will be clear that a minimum number of three lines is required and that, if so desired, more than four lines may be opted for.

If so desired, the number of picture elements in the horizontal direction used for movement detection may be increased. To this end a circuit may, for example, be provided at the output 137, which produces a logic one signal when a desired number of consecutive picture elements produce a logic one signal at the output 137.

It will further be clear that if so desired subcircuits of a different composition may be used when the basic idea of the invention is used, which is based on the possibility to use a field delay when a sign reversal detection circuit is used.

If sodesired, a field period plus half a line period (R+FL) may alternatively be used as a nominal field delay, provided the comparison circuit 1 5 is adapted thereto, so that a comparison of the information from position sequential lines is obtained again.

Claims

1. A movement detection circuit for an interlaced television signal in which in a comparison circuit information from a plurality of consecutive lines is compared with the information from a plurality of corresponding sequential lines which information is obtained from the first-mentioned information by means of a delay circuit, this delay circuit having an output circuit for obtaining a movement indication signal, characterised in that the delay circuit provides a delay of substantially one field period with the comparison circuit arranged for comparing information from a number of position-sequential picture lines in a given field with picture lines correspondingly positioned in the preceding field, a sign reversal detection circuit being cou-pled to the output circuit so that the movement indication signal can only be produced when the sign of differences in the compared information between the two fields is reversed.

2. A movement detection circuit as claimed in Claim 1, characterised in that the field delay circuit provides a time delay of one field period minus half a line period.

3. A movement detection circuit as claimed in Claim 1 or 2, characterised in that the sign reversal detection circuit comprises at least one gate circuit having an exclusive-OR-function.

4. A movement detection circuit substantially as herein described with reference to the accompanying drawings.