Method and apparatus for crispening video signals by the use of temporal filters

Claim 3

The method according to claim 1 comprising the further steps of amplifying said first derivative video signal, prior to adding said first derivative video signal to the present video frame.

Claim 6

The method according to claim 3 comprising the further step of amplifying said processed first derivative video signal prior to its addition to the present video frame.

Claim 7

Apparatus for enhancing the definition of the edges of moving objects in a video signal, or the like, which comprises: means for storing at least two complete frames of said video signal to furnish, at any instant of time, information concerning present, past and future video frames; a first adding circuit connected to the input and output of said storing means thereby to average a past and a future video frame; a subtracting circuit connected to said storing means and to the output of said adding circuit to subtract said averaged video frame from the present video frame thereby to generate a second derivative video signal; and a second adding circuit connected to said storing means and to the output of said subtracting circuit to add the present video frame to said second derivative video signal thereby to generate a video signal in which the definition of the edges of moving objects is enhanced.

Claim 8

Apparatus for enhancing the definition of the edges of moving objects in a video signal, or the like, which comprises: means for storing at least two complete frames of said video signal to furnish, at any instant of time, information concerning present, past and future video frames; a first adding circuit connected to the input and output of said storing means thereby to average a past and a future video frame; a subtracting circuit connected to said storing means and to the output of said adding circuit to subtract said averaged video frame from the present video frame thereby to generate a second derivative video signal; and a second adding circuit connected to said storing means and to the output of said subtracting circuit to add the present video frame to said second derivative video signal thereby to generate a video signal in which the definition of the edges of moving objects is enhanced.

Claim 9

The apparatus according to claim 5 further comprising a buffer-amplifier connected between the output of said subtracting circuit and said second adding circuit.

Claim 10

The apparatus according to claim 5 wherein said storing means is a digital storing means and said apparatus further comprises: an analogue-to-digital converter interposed between the source of said video signal and the input to said storing means; and a digital clock for receiving synchronizing signals for said video signal, said clock being connected to and synchronizing said analogue-to-digital converter and said digital storing means.

Claim 11

The apparatus according to claim 7 wherein said digital storing means comprises first and second digital memories each having a capacity sufficient to store at least one entire video frame, the output of said first digital memory being connected to the input of said second digital memory.

Claim 12

Apparatus for enhancing the definition of the edges of moving objects in a video signal, or the like, which comprises: means for storing at least two complete frames of said video signal to furnish, at any instant of time, information concerning present, past and future video frames; a first adding circuit connected to the input and output of said storing means thereby to average a past and a future video frame; a subtracting circuit connected to said storing means and to the output of said adding circuit to subtract said averaged video frame from the present video frame thereby to generate a second derivative video signal; means, connected to the output of said subtracting circuit, for performing the mathematical operation (SGN (F). MAX (0, F -T)), on the output of said subtracting circuit, where F represents the second derivative signal at said output and T is some threshold level above any noise which may be present in said video signal; and a second adding circuit connected to said storing means and to the output of said performing means to add the present video frame to the output of said performing means thereby to generate a video signal in which the definition of the edges of moving objects is enhanced but the noise is not enhanced.

Claim 13

Apparatus for enhancing the definition of the edges of moving objects in a video signal, or the like, which comprises: means for storing at least two complete frames of said video signal to furnish, at any instant of time, information concerning present, past and future video frames; a first adding circuit connected to the input and output of said storing means thereby to average a past and a future video frame; a subtracting circuit connected to said storing means and to the output of said adding circuit to subtract said averaged video frame from the present video frame thereby to generate a second derivative video signal; means, connected to the output of said subtracting circuit, for performing the mathematical operation (SGN (F). MAX (0, F -T)), on the output of said subtracting circuit, where F represents the second derivative signal at said output and T is some threshold level above any noise which may be present in said video signal; and a second adding circuit connected to said storing means and to the output of said performing means to add the present video frame to the output of said performing means thereby to generate a video signal in which the definition of the edges of moving objects is enhanced but the noise is not enhanced.

Claim 14

The apparatus according to claim 9 further comprising a buffer-amplifier connected between the output of said digital logic circuit and said second adding circuit.

Claim 15

The apparatus according to claim 9 wherein said storing means is a digital storing means and said apparatus further comprises: an analogue-to-digital converter interposed between the source of said video signal and the input to said storing means; and a digital clock for receiving synchronizing signals for said video signal, said clock being connected to and synchronizing said analogue-to-digital converter, said storing means, and said performing means.

Claim 16

The apparatus according to claim 11 wherein said digital storing means comprises first and second digital memories each having a capacity sufficient to store at least one entire video frame, the output of said first digital memory being connected to the input of said second digital memory.

Claim 17

A pre-emphasis circuit for enhancing the higher temporal frequencies in a video signal, or the like, prior to transmission thereof over a transmission facility, which comprises: means for storing at least one complete frame of said video signal to furnish, at any instant of time, information concerning both present and future video frames; a subtractor circuit connected to the input and output of said storing means to subtract the present video frame from a future video frame and thereby generate a first derivative video signal; and an adding circuit connected to the input of said storing means and to the output of said subtractor circuit to add said first derivative video signal to the present video frame, whereby the higher temporal frequencies in said present frame are enhanced.

Claim 18

A pre-emphasis circuit for enhancing the higher temporal frequencies in a video signal, or the like, prior to transmission thereof over a transmission facility, which comprises: means for storing at least one complete frame of said video signal to furnish, at any instant of time, information concerning both present and future video frames; a subtractor circuit connected to the input and output of said storing means to subtract the present video frame from a future video frame and thereby generate a first derivative video signal; and an adding circuit connected to the input of said storing means and to the output of said subtractor circuit to add said first derivative video signal to the present video frame, whereby the higher temporal frequencies in said present frame are enhanced.

Claim 19

The circuit according to claim 13 wherein said storing means is a digital storing means and said apparatus further comprises: an analogue-to-digital converter interposed between the source of said video signal and the input to said digital storing means; and a digital clock for receiving synchronizing signals for sAid video signal, said clock being connected to, and synchronizing, said analogue-to-digital converter and said digital storing means.

Claim 20

The circuit according to claim 13 further comprising: a buffer-amplifier interposed between the output of said subtracting circuit and said adding circuit.

Claim 21

A de-emphasis circuit for restoring a video signal, or the like, in which the higher temporal frequencies were enhanced prior to transmission, which comprises: an adding circuit having an input connected to the source of said video signal; a first amplifier, having a gain of 1/1 + Alpha , connected to the output of said adding circuit; means for storing at least one complete frame of said video signal to furnish, at any instant of time, information concerning present and future video frames, said storing means being connected to the output of said first amplifier; and a feedback loop connecting the output of said storing means to said adding circuit, said feedback loop including a second amplifier having a gain of Alpha , with the output of said de-emphasis circuit being taken from the output of said storing means.

Claim 22

A de-emphasis circuit for restoring a video signal, or the like, in which the higher temporal frequencies were enhanced prior to transmission, which comprises: an adding circuit having an input connected to the source of said video signal; a first amplifier, having a gain of 1/1 + Alpha , connected to the output of said adding circuit; means for storing at least one complete frame of said video signal to furnish, at any instant of time, information concerning present and future video frames, said storing means being connected to the output of said first amplifier; and a feedback loop connecting the output of said storing means to said adding circuit, said feedback loop including a second amplifier having a gain of Alpha , with the output of said de-emphasis circuit being taken from the output of said storing means.

Claim 23

The apparatus according to claim 16 wherein said storing means is a digital storing means and said apparatus further comprises: a digital-to-analogue converter connected to the output of said storing means; and a digital clock connected to the input of said adding circuit to receive synchronizing signals for said video signal, said clock being connected to and synchronizing, said digital-to-analogue converter and said storing means.