Video noise reducer with detection of both total and temporal picture changes
First Claim
1. Apparatus including a fader circuit (C) for reducing noise in a first video signal (A) provided to a first input of said fader circuit (C), said fader circuit having an output, said apparatus having a write-read memory (ST) connected in circuit for delaying a second video signal for essentially a full picture period to produce in a read-out of said write-read memory a delayed second video signal (B) said output of said fader circuit (C) providing said second video signal and being connected to an input of said write-read memory and having said first input and a second input connected for fading together said first video signal (A) and said delayed second video signal (B) at a controllable fading factor (k), a total motion detector (E'"'"', P) including a comparator (E'"'"') connected for comparing corresponding pixels of said delayed second video signal (B) and said first video signal (A) and a control circuit (P), having a preliminary filter (F) for eliminating high frequency noise components, of which an input is connected to an output of said comparator (E'"'"'), wherein said filter output produces a signal (M) representative of the absolute value difference between said corresponding pixels, said control circuit also including a read-only memory (T'"'"') for modifying said fading factor in response to said filter output signal (M) so that, with increasing total motion in a scene defined by said first video signal, the contribution of said delayed second video signal to the output of said fader circuit is reduced, characterized in thatsaid comparator (E'"'"') has a second output (±
- ) for a signal designating the sign of every said difference between corresponding pixels found in comparison of said first video signal and said delayed second video signal by said comparator, in addition to said output of said comparator connected to said control circuit (P);
said read-only memory (T'"'"') of said total motion detector is connected for being addressed jointly by output (M) from said preliminary filter (F) and by at least first and second address signal values, said first address signal value (S1) being a motion-signal-effectiveness threshold value, anda temporal motion detecting logic circuit (TD, TD'"'"' TD") having an input connected to said output (±
) for said sign designating signal of said comparator and an output connected to supply said second address signal value (S3) to an address input of said read-only memory, for at least partially preventing the reduction of the fading factor applied in said fader circuit (C) when designations of the same sign are predominant among sequential sign designations provided by said sign designating signal.
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Accused Products
Abstract
A video noise reducer comprises a full picture memory and provides comparison of corresponding pixels of undelayed and delayed video signals, in which the delayed signal is fed back and mixed which is the undelayed signal at a controllable fader fading factor controlled by the absolute value difference between compared pixels subjected to filtering and other processing. In this noise reducer pixel comparison is elaborated to provide a signal designating the sign of the difference and a temporal (non-spatial) motion detector checks for the predominance of designations of one sign (and the rarity of designations of the other sign) in order to establish the presence of a fading procedure which must not be mistakenly interpreted as a detection of motion in the picture content. The temporal motion detector can be constituted so that isolated designations of a sign opposite to the preponderant sign of a succession of designations of the same sign cannot prevent the recognition of the presence of a fading procedure.
25 Citations
14 Claims
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1. Apparatus including a fader circuit (C) for reducing noise in a first video signal (A) provided to a first input of said fader circuit (C), said fader circuit having an output, said apparatus having a write-read memory (ST) connected in circuit for delaying a second video signal for essentially a full picture period to produce in a read-out of said write-read memory a delayed second video signal (B) said output of said fader circuit (C) providing said second video signal and being connected to an input of said write-read memory and having said first input and a second input connected for fading together said first video signal (A) and said delayed second video signal (B) at a controllable fading factor (k), a total motion detector (E'"'"', P) including a comparator (E'"'"') connected for comparing corresponding pixels of said delayed second video signal (B) and said first video signal (A) and a control circuit (P), having a preliminary filter (F) for eliminating high frequency noise components, of which an input is connected to an output of said comparator (E'"'"'), wherein said filter output produces a signal (M) representative of the absolute value difference between said corresponding pixels, said control circuit also including a read-only memory (T'"'"') for modifying said fading factor in response to said filter output signal (M) so that, with increasing total motion in a scene defined by said first video signal, the contribution of said delayed second video signal to the output of said fader circuit is reduced, characterized in that
said comparator (E'"'"') has a second output (± - ) for a signal designating the sign of every said difference between corresponding pixels found in comparison of said first video signal and said delayed second video signal by said comparator, in addition to said output of said comparator connected to said control circuit (P);
said read-only memory (T'"'"') of said total motion detector is connected for being addressed jointly by output (M) from said preliminary filter (F) and by at least first and second address signal values, said first address signal value (S1) being a motion-signal-effectiveness threshold value, and a temporal motion detecting logic circuit (TD, TD'"'"' TD") having an input connected to said output (±
) for said sign designating signal of said comparator and an output connected to supply said second address signal value (S3) to an address input of said read-only memory, for at least partially preventing the reduction of the fading factor applied in said fader circuit (C) when designations of the same sign are predominant among sequential sign designations provided by said sign designating signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
- ) for a signal designating the sign of every said difference between corresponding pixels found in comparison of said first video signal and said delayed second video signal by said comparator, in addition to said output of said comparator connected to said control circuit (P);
Specification