Deemphasis and subsequent reemphasis of high-energy reversed-spectrum components of a folded video signal

• US 5,596,418 A
• Filed: 06/07/1995
• Issued: 01/21/1997
• Est. Priority Date: 08/17/1990
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Yun, Jong K., Limberg, Allen L., Ko, Jung W., Strolle, Christopher H., Weckenbrock, Hermann J., Wedam, Werner F., Schnitzler, Raymond
• Primary Examiner(s): Tran, Thai Q.
• Assistant Examiner(s): Truong, Khoi
• Application Number:
  US08/478,766
• Time in Patent Office: 594 Days
• Field of Search: 358/310, 358/315, 358/316, 358/318, 348/426, 348/427, 348/436, 348/437, 348/438, 348/663, 348/666, 348/708, 348/712
• US Class Current: 386/304
• CPC Class Codes: H04N 5/923 using preemphasis of the signal before modulation and deemphasis of the signal after demodulation volume compression or expansion in amplifiers in general H03G7/00
• CPC Class Codes: H04N 9/7976 by spectrum folding of the high frequency components of the luminance signal
• CPC Class Codes: H04N 9/80 Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback
• CPC Class Codes: H04N 9/8205 involving the multiplexing of an additional signal and the colour video signal
• CPC Class Codes: H04N 9/898 using frequency multiplication of the reproduced colour signal carrier with another auxiliary reproduced signal, e.g. a pilot signal carrier H04N9/83 takes precedence

Abstract

A system for reproducing a luminance signal from a medium containing a previously recorded luminance signal with a high-frequency portion thereof compressed in dynamic range includes a circuit for recovering that luminance signal from the medium. Filtering is done to separate the low-frequency and compressed-in-dynamic-range high-frequency portions of the recovered luminance signal from each other. A corer responds to the separated compressed-in-dynamic-range high-frequency portion of the recovered luminance signal to provide a cored high-frequency portion with expanded dynamic range and reduced noise. The level of the cored high-frequency portion with expanded dynamic range and reduced noise is then boosted by a predetermined amount to compensate for energy losses during the compression of the dynamic range and added back to the low-frequency portion of the recovered luminance signal to reproduce a full-band luminance signal with at least partially restored dynamic range for high-frequencies and without readily visible high-frequency noise.

Claims

1. A recording system for recording on a recording medium a representation of a luminance signal received for recording, said recording system comprising:

means, responding to said luminance signal received for recording, for producing a control signal indicative of a desired amount of reduction of a high-frequency portion of said luminance signal vis-a-vis a low-frequency portion of said luminance signal during recording;

means for reducing the level of the high-frequency portion of said luminance signal by said desired amount in response to said control signal, thereby to generate a luminance signal with deemphasized high frequencies; and

means for recording on said medium said luminance signal with deemphasized high frequencies, wherein said means for producing a control signal comprises;

means for separating from said luminance signal received for recording a high-frequency portion thereof;

a rectifier connected for generating a rectified response to said high-frequency portion separated from said luminance signal;

a threshold circuit connected for responding only to those portions of said rectified response exceeding said threshold level; and

a lowpass filter connected for producing said control signal in response to the response of said threshold circuit, for reducing the level of the high-frequency portion of said luminance signal only if the level of said separated high-frequency portion exceeds a predetermined threshold level.

2. A recording system, as set forth in claim 1, wherein said means for separating said high-frequency portion from said luminance signal received for recording comprises a highpass filter.

3. A recording system, as set forth in claim 1, wherein said control signal has an amplitude indicative of said desired amount of reduction of the high-frequency portion of said luminance signal vis-a-vis its low-frequency portion, and wherein said means for reducing the level of the high-frequency portion of said luminance signal includes:

means for generating a multiplier signal having an amplitude that varies in response to said control signal, growing smaller with increase in said control signal and growing larger with decrease in said control signal;

means for multiplying the separated high-frequency portion of said luminance signal by said multiplier signal, thereby to generate a product signal;

means for separating from said luminance signal received for recording a low-frequency portion thereof; and

means for additively combining with said product signal the separated low-frequency portion of said luminance signal received for recording, thereby to generate said luminance signal with deemphasized high frequencies.

4. A recording system as set forth in claim 3 wherein said means for generating a multiplier signal essentially consists of:

means for subtracting said control signal from a prescribed level for generating said multiplier signal.

5. A recording system as set forth in claim 4 wherein said means for separating from said luminance signal received for recording a low-frequency portion thereof comprises, in addition to said means for separating from said luminance signal received for recording a high-frequency portion thereof, means for differentially combining said luminance signal received for recording and said separated high-frequency portion thereof.

6. A recording system as set forth in claim 1, in combination with a reproducing system for reproducing said luminance signal from said representation thereof recorded on said recording medium, said reproducing system comprising:

means for recovering from said medium said luminance signal with deemphasized high frequencies; and

means for boosting the level of the high-frequency portion of the recovered luminance signal with deemphasized high frequencies, thereby to reproduce said luminance signal as received for recording.

7. A combination as set forth in claim 6, wherein in said reproducing system said means for boosting the level of the high-frequency portion of said luminance signal with deemphasized high frequencies comprises:

means for separating the low-frequency and high-frequency portions of said recovered luminance signal with deemphasized high frequencies from each other;

means for coring the separated high-frequency portion of said recovered luminance signal;

means for boosting the level of said cored high-frequency portion of said recovered luminance signal by a scaling factor, thereby to generate reemphasized luminance high-frequencies; and

means for additively combining said reemphasized luminance high-frequencies with the separated low-frequency portion of said recovered luminance signal, thereby to reproduce said luminance signal as received for recording.

8. A combination as set forth in claim 6, wherein in said reproducing system said means for boosting the level of the high-frequency portion of said luminance signal with deemphasized high frequencies comprises:

means for separating from said recovered luminance signal with deemphasized high frequencies the high-frequency portion thereof;

means for coring the separated high-frequency portion of said recovered luminance signal, thereby to generate a cored response to the high-frequency portion of said recovered luminance signal; and

means for additively combining with said recovered luminance signal said cored response to the high-frequency portion of said recovered luminance signal, thereby to reproduce said luminance signal as received for recording.

9. A recording system for recording on a recording medium representations of a full-spectrum luminance signal received for recording, said recording system comprising:

means for separating from said luminance signal received for recording an upper-frequency portion thereof that comprises those spectral components in an upper-frequency band extending above a crossover frequency;

a rectifier connected for generating a rectified response to said upper-frequency portion separated from said luminance signal received for recording;

a threshold circuit connected for responding only to those portions of said rectified response exceeding a threshold level;

a lowpass filter connected for producing in response to the response of said threshold circuit a control signal, which control signal is dependent on the amount the level of said upper-frequency portion exceeds a predetermined threshold level;

means for generating a folded-spectrum luminance signal that occupies just a lower-frequency band extending below a crossover frequency, which means includes

means for translating said upper-frequency portion of said full-spectrum luminance signal received for recording into the lower-frequency band also occupied by a lower-frequency portion of said full-spectrum luminance signal received for recording, thereby generating a folded luminance signal;

means responsive to said control signal for reducing in said folded luminance signal the level of that portion of said full-spectrum luminance signal which is translated from the upper-frequency band into the lower-frequency band, vis-a-vis those portions of said full-spectrum luminance signal which originally are in the lower-frequency band; and

means for recording on said medium said folded luminance signal.

10. A recording system, as set forth in claim 9, wherein said means for separating from said luminance signal received for recording an upper-frequency portion thereof comprises a highpass filter.

11. A system for recording as set forth in claim 9 in combination with

a reproducing system for recovering during play back from said recording medium a replica of said full-spectrum luminance signal received for recording, which said reproducing system comprises:

means for recovering from said medium said folded luminance signal;

means for unfolding said folded luminance signal to generate an unfolded luminance signal; and

means for generating in response to said unfolded luminance signal said replica of said full-spectrum luminance signal received for recording, which said means for generating includes

means for boosting the level of the upper-frequency portion of said unfolded luminance signal as it appears in said replica of said full-spectrum luminance signal received for recording.

12. A combination as set forth in claim 11, wherein in said reproducing system said means for boosting the level of the upper-frequency portion of said unfolded luminance signal comprises:

means for separating the lower-frequency and upper-frequency portions of said unfolded luminance signal from each other;

means for coring the separated high-frequency portion of said unfolded luminance signal;

means for boosting the level of said cored high-frequency portion of said unfolded luminance signal by a scaling factor, thereby to generate reemphasized luminance high-frequencies; and

means for additively combining said reemphasized luminance high-frequencies with the separated low-frequency portion of said unfolded luminance signal, thereby to generate said replica of said full-spectrum luminance signal received for recording.

13. A combination as set forth in claim 11, wherein in said reproducing system said means for boosting the level of the upper-frequency portion of said unfolded luminance signal comprises:

means for separating from said unfolded luminance signal the upper-frequency portion thereof;

means for coring the separated upper-frequency portion of said unfolded luminance signal, thereby to generate a cored response to the high-frequency portion of said unfolded luminance signal; and

means for additively combining with said unfolded luminance signal said cored response to the upper-frequency portion of said unfolded luminance signal, thereby to generate said replica of said full-spectrum luminance signal received for recording.

14. A recording system for recording on a recording medium representations of a full-spectrum luminance signal received for recording said recording system comprising:

a band-separation filter responding to said luminance signal received for recording for separating lower-frequency and upper-frequency portions thereof, said lower-frequency portion comprising only those spectral components in a lower-frequency band extending up to a crossover frequency, and said upper-frequency portion comprising only those spectral components in an upper-frequency band extending above a crossover frequency;

a rectifier connected for generating a rectified response to said upper-frequency portion separated from said luminance signal received for recording;

a threshold circuit connected for responding only to those portions of said rectified response exceeding a threshold level;

a lowpass filter connected for producing in response to the response of said threshold circuit a control signal, which control signal is dependent on the amount the level of said upper-frequency portion exceeds a predetermined threshold level;

means responsive to said control signal for generating a multiplier signal the amplitude of which grows smaller in response to increase in said control signal and grows larger in response to decrease in said control signal;

means for multiplying by said multiplier signal the separated upper-frequency portion of said luminance signal received for recording, thereby to generate a product signal;

means for additively combining said product signal with the separated lower-frequency portion of said luminance signal received for recording, thereby to generate a full-spectrum luminance signal with deemphasized high frequencies;

means, responsive to said full-spectrum luminance signal with deemphasized high frequencies, for generating a folded-spectrum luminance signal that occupies just a lower-frequency band extending below said crossover frequency, which means includes

means for translating said upper-frequency portion of said full-spectrum luminance signal with deemphasized high frequencies into the lower-frequency band also occupied by a lower-frequency portion of said full-spectrum luminance signal with deemphasized high frequencies, thereby generating a folded luminance signal; and

means for recording on said medium said folded luminance signal.

15. A recording system, as set forth in claim 14, wherein said band-separation filter comprises:

a highpass filter responding to said luminance signal received for recording for separating the upper-frequency portion thereof; and

means for supplying a differential response to said luminance signal received for recording and the separated upper-frequency portion thereof, said differential response corresponding to the separated lower-frequency portion of said luminance signal received for recording.

16. A recording system, as set forth in claim 14, wherein said means responsive to said control signal for generating a multiplier signal essentially consists of:

means for subtracting said control signal from a prescribed level for generating said multiplier signal.

17. A system for recording as set forth in claim 14 in combination with

a reproducing system for recovering during play back from said recording medium a replica of said full-spectrum luminance signal received for recording, which said reproducing system comprises:

means for recovering from said medium said folded luminance signal;

means for unfolding said folded luminance signal to generate an unfolded luminance signal; and

means for generating in response to said unfolded luminance signal said replica of said full-spectrum luminance signal received for recording which said means for generating includes

means for boosting the level of the upper-frequency portion of said unfolded luminance signal as it appears in said replica of said full-spectrum luminance signal received for recording.

18. A combination as set forth in claim 17, wherein in said reproducing system said means for boosting the level of the upper-frequency portion of said unfolded luminance signal comprises:

means for separating the lower-frequency and upper-frequency portions of said unfolded luminance signal from each other;

means for coring the separated high-frequency portion of said unfolded luminance signal;

means for boosting the level of said cored high-frequency portion of said unfolded luminance signal by a scaling factor, thereby to generate reemphasized luminance high-frequencies; and

means for additively combining said reemphasized luminance high-frequencies with the separated low-frequency portion of said unfolded luminance signal, thereby to generate said replica of said full-spectrum luminance signal received for recording.

19. A combination as set forth in claim 17, wherein in said reproducing system said means for boosting the level of the upper-frequency portion of said unfolded luminance signal comprises:

means for separating from said unfolded luminance signal the upper-frequency portion thereof;

means for coring the separated upper-frequency portion of said unfolded luminance signal, thereby to generate a cored response to the high-frequency portion of said unfolded luminance signal; and

means for additively combining with said unfolded luminance signal said cored response to the upper-frequency portion of said unfolded luminance signal, thereby to generate said replica of said full-spectrum luminance signal received for recording.