Computer graphics processing and selective visual display system – Computer graphics processing – Attributes
Reexamination Certificate
2000-03-03
2003-02-18
Razavi, Michael (Department: 2672)
Computer graphics processing and selective visual display system
Computer graphics processing
Attributes
C345S698000, C345S699000, C348S222100
Reexamination Certificate
active
06522339
ABSTRACT:
FIELD OF THE INVENTION
This invention relates a method and a device for converting the resolution of picture signal as well as converting interlace system picture signal into non-interlace system picture signal, which are applicable to displays, such as plasma display and LC (liquid crystal) display, to display pictures in non-interlace system.
BACKGROUND OF THE INVENTION
In general, a frame in NTSC television broadcasting is composed of 525 scanning lines (or lines). Moving image is created by sending 30 frames per 1 second. However, in case of 30 frames per 1 second, it is likely to sense some flicker. So, to reduce the flicker in displaying moving image, the interlace system is used.
The interlace system which is one of image displaying systems means “interlaced scanning”. In the interlace system, the scanning from top to bottom is conducted every other line. Thus, by finishing one frame in half time, the flicker is reduced. A complete picture (frame) is created using two frames (fields) each of which is composed of 262.5 scanning lines.
On the other hand, with plasma display or LC display, when displaying in the interlace system, all the more flicker occurs and the brightness lowers. Because of this, the non-interlace system (also called progressive system) which is “sequential scanning” is used. So, in plasma displays or LC displays, interlace system picture signal needs to be converted into non-interlace system picture signal.
Although picture signal with 525 scanning lines is obtained by converting interlace system picture signal of 262.5 scanning lines into non-interlace system picture signal, plasma displays may be used to display at a resolution with more than (or less than) 525 scanning lines. In such a case, the resolution of picture signal also needs to be converted.
FIG. 1
is a block diagram showing the composition of a conventional resolution conversion device applicable to such a case. In
FIG. 1
, a two-dimensional scanline interpolation circuit
1
interpolates (estimates a value to be laid between different values from the whole tendency) intermediate picture signal (picture signals between scanning lines) based on picture signal of 262.5 scanning lines, inserting 262.5 interpolation scanning lines into the intervals of 262.5 scanning lines in one field. Thereby, interlace system picture signal of 262.5 scanning lines is converted into non-interlace system picture signal of 525 scanning lines.
A three-dimensional scanline interpolation circuit
2
interpolates picture signal based on picture signal of 262.5 scanning lines in the previous field (or the previous and following fields), inserting 262.5 interpolation scanning lines into the intervals of 262.5 scanning lines in the current field. Thereby, interlace system picture signal of 262.5 scanning lines is converted into noninterlace system picture signal of 525 scanning lines.
A movement detection circuit
3
stores picture signal into frame memory, detecting the difference between previous-frame picture signal and current-frame picture signal, thereby detecting the degree of movement in moving image. A coefficient generator circuit
4
determines a degree of movement in moving image based on difference signal output from the movement detection circuit
3
, generating coefficients &agr;, &bgr; according to the degree of movement.
A coefficient multiplier
5
multiplies non-interlace system picture signal output from the two-dimensional scanline interpolation circuit
1
by coefficient &bgr; (=1−&agr;) output from the coefficient generator circuit
4
. A coefficient multiplier
6
multiplies non-interlace system picture signal output from the three-dimensional scanline interpolation circuit
2
by coefficient &agr; (0≦&agr;≦1) output from the coefficient generator circuit
4
. An adder
7
adds picture signals output from the coefficient multipliers
5
and
6
.
A resolution converter circuit
8
converts non-interlace system picture signal of 525 scanning lines output from the adder
7
into picture signal at a given resolution (e.g., of 768 scanning lines). As the resolution conversion method, linear interpolation to weight, based on the position of scanning line to be interpolated and the distance of scanning line in the current field, a reciprocal number of the distance is used. Also, besides the linear interpolation, curve interpolation to weight using a spline function (curve) can be used.
Also, the resolution converter circuit
8
may conduct the conversion of resolution in the horizontal direction (for dots), other than the conversion of resolution in the vertical direction (for scanning line number).
In operation, interlace system picture signal is, as shown in
FIG. 1
, input to the two-dimensional scanline interpolation circuit
1
, three-dimensional scanline interpolation circuit
2
and movement detection circuit
3
.
For interlace system picture signal of 262.5 scanning lines, the two-dimensional scanline interpolation circuit
1
interpolates picture signal between scanning lines based on the picture signal of 262.5 scanning lines laid every other line in one field, inserting 262.5 interpolation scanning lines into the intervals of 262.5 scanning lines in one field. Thereby, the interlace system picture signal is converted into non-interlace system picture signal of 525 scanning lines.
Also, for interlace system picture signal of 262.5 scanning lines, the three-dimensional scanline interpolation circuit
2
interpolates picture signal based on the picture signal of 262.5 scanning lines in the previous field (or the previous and following fields), inserting 262.5 interpolation scanning lines into the intervals of 262.5 scanning lines in the current field. Thereby, the interlace system picture signal is converted into non-interlace system picture signal of 525 scanning lines.
For interlace system picture signal of 262.5 scanning lines, the movement detection circuit
3
detects the difference between the previous-frame picture signal and the current-frame picture signal, then outputting it to the coefficient generator circuit
4
. The coefficient generator circuit
4
determines a degree of movement in moving image based on the difference signal output from the movement detection circuit
3
, outputting coefficients &agr;, &bgr;, according to the degree of movement, to the coefficient multipliers
5
and
6
.
Coefficients &agr;, &bgr; generated by the coefficient generator circuit
4
are in relations of &bgr;=1−&agr; and 0≦&agr;≦1. As coefficient &agr; increases, coefficient &bgr; decreases. On the contrary, as coefficient &bgr; increases, coefficient &agr; decreases. Here, when degree of movement is low, the coefficient generator circuit
4
increases coefficient &agr; to increment the influence of picture signal (static image) output from the three-dimensional scanline interpolation circuit
2
. When degree of movement is high, the coefficient generator circuit
4
increases coefficient &bgr; to increment the influence of picture signal (dynamic image) output from the two-dimensional scanline interpolation circuit
1
. Such signal processing based on the degree of movement in moving image is called movement-adaptive signal processing.
Non-interlace system picture signal (of 525 scanning lines) output from the two-dimensional scanline interpolation circuit
1
is multiplied by coefficient &bgr; by the coefficient multiplier
5
, then output to the adder
7
. Also, non-interlace system picture signal (of 525 scanning lines) output from the three-dimensional scanline interpolation circuit
2
is multiplied by coefficient &agr; by the coefficient multiplier
6
, then output to the adder
7
. The two non-interlace system picture signals (of 525 scanning lines) are added by the adder
7
, then output to the resolution converter circuit
8
.
Then, in case of linear interpolation, the resolution converter circuit &agr; interpolates the noninterlace system picture signal (of 525 scanning lines) to weight, based on the position of scanning line to be interpolate
Havan Thu-Thao
Razavi Michael
Young & Thompson
LandOfFree
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