Scan conversion apparatus with improved vertical resolution and flicker reduction apparatus

Claim 2

The scan conversion apparatus of claim 1, wherein said deflickering circuit (30, 220) comprises: a vertical filtering circuit for separating high and low vertical spatial frequency components of said video input signal, thereby producing a vertical high-frequency signal and a vertical low-frequency signal; a horizontal filtering circuit for extracting high horizontal spatial frequency components of said vertical high-frequency signal, thereby producing a horizontal-highfrequency-vertical-high-frequency signal; and an adder (78) for adding said horizontal-highfrequency-vertical-high-frequency signal to said vertical low-frequency signal to produce said filtered video signal.

Claim 3

The scan conversion apparatus of claim 2, wherein said deflickering circuit (30, 220) also comprises: an amplitude converting circuit (182) coupled between said horizontal filtering circuit and said adder (78), for modifying said horizontal-high-frequency-vertical-highfrequency signal in amplitude before input to said adder (78).

Claim 4

The scan conversion apparatus of claim 1, wherein said deflickering circuit (30, 220) separates said video input signal into a first component simultaneously having both high vertical spatial frequency and low horizontal spatial frequency, and a second component not simultaneously having both high vertical spatial frequency and low horizontal spatial frequency, and comprises: an amplitude limiter (128, 171, 185) for limiting said first component in amplitude to produce a limited first component; and an adder (78) for adding said limited first component to said second component to produce said filtered video signal.

Claim 5

The scan conversion apparatus of claim 4, wherein said amplitude limiter (171, 185) operates with different limiting characteristics responsive to a control signal, further comprising: a direct-current detector (172, 183) for generating said control signal by detecting direct-current-like portions of said video input signal.

Claim 6

The scan conversion apparatus of claim 5, wherein: when said direct-current detector (172, 183) detects a direct-current-like portion of said input video signal, said amplitude limiter (185) reduces said first component in amplitude and reverses said first component in sign; and when said direct-current detector (172, 183) does not detect a direct-current-like portion of said input video signal, said amplitude limiter (185) limits said first component to a certain maximum amplitude.

Claim 7

The scan conversion apparatus of claim 5, wherein said deflickering circuit (30, 220) separates high vertical spatial frequency components of said video input signal from low vertical spatial frequency components of said video input signal, and said direct-current detector (183) generates said control signal by detecting direct-current-like portions of said high vertical spatial frequency components.

Claim 8

The scan conversion apparatus of claim 5, wherein said deflickering circuit (30, 220) extracts, as part of said second component, a signal having high horizontal spatial frequency, said direct-current detector (183) compares said signal having high horizontal spatial frequency with a threshold value, and said direct-current detector (183) detects a direct-current-like portion when said signal having high horizontal spatial frequency has an absolute value less than said threshold value.

Claim 9

A scan conversion apparatus for converting a video input signal having progressively scanned even and odd horizontal scanning lines and made up of red, green, and blue component signals to a video output signal in which said even and odd horizontal scanning lines are scanned in an interlaced manner, and for reducing flicker in said video output signal, comprising: a matrix circuit (18) for converting said red, green, and blue component signals into a luminance signal and two chrominance signals; a deflickering circuit (30, 220) coupled to said matrix circuit (18), for attenuating spatial frequency components of said luminance signal combining high vertical spatial frequency with low horizontal spatial frequency, thereby producing a filtered luminance signal; a first scan conversion means (32) coupled to said deflickering circuit (30, 220), for converting said filtered luminance signal and said chrominance signals from progressive scanning to interlaced scanning; and a pair of second scan conversion means (34, 36) coupled to said matrix circuit (18), for converting said chrominance signals from progressive scanning to interlaced scanning.

Claim 10

The scan conversion apparatus of claim 9, further comprising a pair of low-pass filters (22, 24) coupled between said matrix circuit (18) and said second scan conversion means (34, 36), for limiting said chrominance signals in bandwidth, wherein: said first scan conversion means (32) receives said filtered luminance signal at a first rate; and said second scan conversion means (34, 36) receive said chrominance signals at a second rate equal to at most one-half of said first rate.

Claim 11

A scan conversion apparatus for converting a video input signal having progressively scanned even and odd horizontal scanning lines to a video output signal in which said even and odd horizontal scanning lines are scanned in an interlaced manner, and for reducing flicker in said video output signal, comprising: a horizontal filtering circuit for separating high and low horizontal spatial frequency components of said video input signal, thereby producing a horizontal high-frequency signal and a horizontal low-frequency signal; a first vertical filtering circuit (68) for attenuating high vertical spatial frequencies in said horizontal low-frequency signal by a first amount; a second vertical filtering circuit (132) for attenuating high vertical spatial frequencies in said horizontal high-frequency signal by a second amount less than said first amount; an adder (78) for adding respective outputs of said first vertical filtering circuit (68) and said second vertical filtering circuit (132) to produce said filtered video signal; and a scan conversion means (32) coupled to said adder (78), for converting said filtered video signal from progressive scanning to interlaced scanning.

Claim 12

A scan conversion apparatus for converting a video input signal having progressively scanned even and odd horizontal scanning lines to a video output signal in which said even and odd horizontal scanning lines are scanned in an interlaced manner, and for reducing flicker in said video output signal, comprising: a vertical filtering circuit for separating high and low vertical spatial frequency components of said video input signal, thereby producing a vertical high-frequency signal and a vertical low-frequency signal; an amplitude limiter (171, 185) coupled to said vertical filtering circuit, for limiting said vertical high-frequency signal in amplitude to produce a limited vertical high-frequency signal, said amplitude limiter (171, 185) operating with different limiting characteristics responsive to a control signal; a direct-current detector (172, 183) coupled to said amplitude limiter (171, 185), for generating said control signal by detecting direct-current-like portions of said video input signal; an adder (78) for adding said limited vertical high-frequency signal to said vertical low-frequency signal to produce said filtered video signal; and a scan conversion means (32) coupled to said adder (78), for converting said filtered video signal from progressive scanning to interlaced scanning.

Claim 13

The scan conversion apparatus of claim 12, wherein: when said direct-current detector (172, 183) detects a direct-current-like portion of said input video signal, said amplitude limiter (185) reduces said vertical high-frequency signal in amplitude and reverses said vertical high-frequency in sign; and when said direct-current detector (172, 183) does not detect a direct-current-like portion of said input video signal, said amplitude limiter (185) limits said vertical high-frequency signal to a certain maximum amplitude.

Claim 14

The scan conversion apparatus of claim 12, wherein said direct-current detector (172, 183) detects direct-current-like portions of said video input signal by detecting direct-current-like portions of said vertical high-frequency signal.

Claim 15

The scan conversion apparatus of claim 12, further comprising a horizontal filtering circuit (74) coupled to said vertical filtering circuit, for extracting a horizontal high-frequency component of said vertical high-frequency signal, wherein: said direct-current detector (183) compares said horizontal high-frequency component of said vertical high-frequency signal with a threshold value, and detects a direct-current-like portion of said video input signal when said horizontal high-frequency component of said vertical high-frequency signal has an absolute value less than said threshold value.

Claim 16

A scan conversion apparatus for converting a video input signal having progressively scanned even and odd horizontal scanning lines to a video output signal in which said even and odd horizontal scanning lines are scanned in an interlaced manner, and for reducing flicker in said video output signal, comprising: a deflickering circuit (30, 220) for attenuating flicker in said video input signal, thereby producing a filtered video signal; a control circuit (222) for receiving expansion information and causing said deflickering circuit (220) to expand a selected part of said input video signal vertically by vertical interpolation followed by vertical low-pass filtering, responsive to said expansion information; a horizontal interpolating circuit (226) coupled to said control circuit (222) for expanding said selected part horizontally by horizontal interpolation; and a scan conversion means (32) coupled to said adder (78), for converting said filtered video signal from progressive scanning to interlaced scanning.

Claim 17

The scan conversion apparatus of claim 16, wherein said horizontal interpolating circuit (226) is coupled to an output side of said scan conversion means (32) and performs horizontal interpolation after said filtered video signal has been converted from progressive scanning to interlaced scanning.

Claim 18

The scan conversion apparatus of claim 16, wherein said input video signal is made up of a luminance signal and two chrominance signals and said deflickering circuit (220) processes only said luminance signal, further comprising: a pair of chrominance scan conversion means (34, 36) controlled by said control circuit (222), for converting said chrominance signals from progressive scanning to interlaced scanning, and expanding said chrominance signals vertically within said selected part of said input video signal.

Claim 19

A flicker reduction apparatus for reducing flicker in an interlaced video signal received a field at a time, comprising: a field-frame conversion circuit for temporarily storing said interlaced video signal, converting said interlaced video signal to a progressively scanned video signal, and outputting said progressively scanned video signal a frame at a time; and a deflickering circuit (30, 220) coupled to said field-frame conversion circuit, for attenuating spatial frequency components of said progressively scanned video signal combining high vertical spatial frequency with low horizontal spatial frequency.

Claim 20

A flicker reduction apparatus for reducing flicker in an interlaced video signal received a field at a time, comprising: a field-frame conversion circuit for temporarily storing said interlaced video signal, converting said interlaced video signal to a progressively scanned video signal, and outputting said progressively scanned video signal a frame at a time; a frequency separating circuit coupled to said field-frame conversion circuit, for separating from said progressively scanned video signal a first component signal combining high vertical spatial frequency with low horizontal spatial frequency; a filtering circuit coupled to said field-frame conversion circuit, for attenuating spatial frequency components of said progressively scanned video signal simultaneously having both high vertical spatial frequency and low horizontal spatial frequency, thereby producing a second component signal; an amplitude limiter (128, 171, 185) coupled to said frequency separating circuit, for limiting said first component signal in amplitude to produce a limited first component signal; and an adder (78) coupled to said amplitude limiter, for adding said limited first component signal to said second component signal.

Claim 21

A flicker reduction apparatus for reducing flicker in an interlaced video signal received a field at a time, comprising: a field-frame conversion circuit for temporarily storing said interlaced video signal, converting said interlaced video signal to a progressively scanned video signal, and outputting said progressively scanned video signal a frame at a time; a horizontal filtering circuit coupled to said field-frame conversion circuit, for separating high and low horizontal spatial frequency components of said video input signal, thereby producing a horizontal high-frequency signal and a horizontal low-frequency signal; a first vertical filtering circuit (68) coupled to said horizontal filtering circuit, for attenuating high vertical spatial frequencies in said horizontal low-frequency signal by a first amount; a second vertical filtering circuit (132) coupled to said horizontal filtering circuit, for attenuating high vertical spatial frequencies in said horizontal high-frequency signal by a second amount less than said first amount; and an adder (78) coupled to said second vertical filtering circuit, for adding respective outputs of said first vertical filtering circuit (68) and said second vertical filtering circuit (132).

Claim 22

A flicker reduction apparatus for reducing flicker in an interlaced video signal received a field at a time, comprising: a field-frame conversion circuit for temporarily storing said interlaced video signal, converting said interlaced video signal to a progressively scanned video signal, and outputting said progressively scanned video signal a frame at a time; a vertical filtering circuit coupled to said field-frame conversion circuit, for separating high and low vertical spatial frequency components of said progressively scanned video signal, thereby producing a vertical high-frequency signal and a vertical low-frequency signal; a horizontal filtering circuit coupled to said vertical filtering circuit, for separating high and low horizontal spatial frequency components of said vertical high-frequency signal, thereby producing a horizontal-high-frequency-vertical-high-frequency signal and a horizontal-low-frequency-vertical-high-frequency signal; an amplitude converting circuit (171) coupled to said horizontal filtering circuit, for modifying said horizontal-low-frequency-vertical-high-frequency signal in amplitude to produce a modified horizontal-low-frequency-vertical-highfrequency signal, said amplitude converting circuit operating with at least two different input-output characteristics responsive to a control signal; a direct-current detector (172, 183) coupled to said amplitude converting circuit, for generating said control signal by detecting direct-current-like portions of said progressively scanned video signal; and an adder coupled to said amplitude converting circuit, for adding said vertical low-frequency signal, said horizontal-high-frequency-vertical-high-frequency signal, and said modified horizontal-low-frequency-vertical-highfrequency signal together.

Claim 23

A flicker reduction apparatus for reducing flicker in an interlaced video signal received a field at a time, comprising: a field-frame conversion circuit for temporarily storing said interlaced video signal, converting said interlaced video signal to a progressively scanned video signal, and outputting said progressively scanned video signal a frame at a time; a vertical filtering circuit coupled to said field-frame conversion circuit, for separating high and low vertical spatial frequency components of said progressively scanned video signal, thereby producing a vertical high-frequency signal and a vertical low-frequency signal; a horizontal filtering circuit (74) coupled to said vertical filtering circuit, for attenuating low horizontal spatial frequency components of said vertical high-frequency signal, thereby producing a horizontal-high-frequency-vertical-high-frequency signal; an amplitude converting circuit (182) coupled to said horizontal filtering circuit, for modifying said horizontal-high-frequency-vertical-high-frequency signal in amplitude to produce a modified horizontal-high-frequency-vertical-high-frequency signal; and an adder (78) coupled to said amplitude converting circuit, for adding said modified horizontal-high-frequency-vertical-high-frequency signal to said vertical low-frequency signal.

Claim 24

A flicker reduction apparatus for reducing flicker in an interlaced video signal received a field at a time, comprising: a field-frame conversion circuit for temporarily storing said interlaced video signal, converting said interlaced video signal to a progressively scanned video signal, and outputting said progressively scanned video signal a frame at a time; a vertical filtering circuit (154) coupled to said field-frame conversion circuit, for separating high and low vertical spatial frequency components of said progressively scanned video signal, thereby producing a vertical high-frequency signal and a vertical low-frequency signal; an amplitude converting circuit (171, 185) coupled to said vertical filtering circuit, for modifying said vertical high-frequency signal in amplitude to produce a modified vertical high-frequency signal, said amplitude converting circuit operating with at least two different input-output characteristics responsive to a control signal; a direct-current detector (172) coupled to said amplitude converting circuit, for generating said control signal by detecting direct-current-like portions of said video input signal; and an adder (173) coupled to said amplitude converting circuit, for adding said vertical low-frequency signal to said modified vertical high-frequency signal.

Claim 25

A scan conversion apparatus for converting a video signal from a progressively scanned format to an interlaced format, comprising a deflickering means for attenuating a high vertical spatial frequency component of the video signal wherein the deflickering means attenuates to a greater extent video signal having a relatively low horizontal spatial frequency.

Claim 26

A scan conversion apparatus for converting a video signal from a progressively scanned format to an interlaced format, comprising an expansion means for expanding a selected part of said input signal, and a deflickering circuit which attenuates flicker in the interlaced video signal by low-pass vertical spatial frequency filtering of the selected part when at least partially expanded.

Claim 27

A scan conversion apparatus for converting a video signal from a progressively scanned format to an interlaced format, comprising an expansion means for expanding a selected part of the video signal by vertical interpolation and for performing the progressive-to-interlaced scan conversion, and a separate horizontal interpolating circuit for expanding the selected part horizontally after the progressive-to-interlaced scan conversion.