System for transmitting facsimile data in the upper vestigial chrominance sideband of a video signal

• US 5,666,168 A
• Filed: 04/08/1994
• Issued: 09/09/1997
• Est. Priority Date: 06/14/1991
• Status: Expired due to Fees

• Current Assignee: WAVO Corporation
• Original Assignee: WavePhore, Inc.
• Inventors: Montgomery, Gerald D., Norrish, Jay B.
• Primary Examiner(s): Peng, John K.
• Assistant Examiner(s): Flynn, Nathan J.
• Application Number:
  US08/224,733
• Time in Patent Office: 1,250 Days
• Field of Search: 348/6-8, 348/17, 348/473-475, 348/461, 348/432, 348/433, 348/436, 348/665, 348/607, 348/608, 348/478, 348/464, 348/468, 348/476, 348/385, 348/386, 348/389 , 348/22-24, 348/18, 348/427, 348/429, 348/430, 348/437, 348/438, 348/460, 348/467, 348/469, 348/486, 348/488, 348/492
• US Class Current: 348/473
• CPC Class Codes: H04N 1/00098 via a television channel, e.g. for a series of still pictures with or without sound
• CPC Class Codes: H04N 5/445 for displaying additional information H04N5/50 takes precedence
• CPC Class Codes: H04N 7/0803 using frequency interleaving, e.g. with precision offset
• CPC Class Codes: H04N 7/081 the additional information signals being transmitted by means of a subcarrier
• CPC Class Codes: H04N 7/10 Adaptations for transmission by electrical cable H04N7/12 takes precedence

Abstract

The instant application is directed to a cable facsimile machine which implements the upper vestigial chrominance sideband of a standard video signal for data transmission.

Signal processors for permitting the transparent, simultaneous transmission and reception of a data signal in the video bandwidth is disclosed. The signal processor in the transmitter rasterizes the data at the horizontal scanning rate and modulates the data with a data carrier at a non-integral multiple of the horizontal scanning rate to obtain frequency interleaving. The data is transmitted during the active video portion of each video line.

Claims

1. A facsimile machine for injecting an image into a video signal having a bandwidth and chrominance subcarrier, the facsimile machine comprising:

means for scanning an image to obtain a digital representation of that image;

means responsive to the scanning means for modulating a data carrier based upon the digital representation to provide a modulated signal; and

means for injecting the modulated signal into the video bandwidth at a frequency greater than the chrominance subcarrier.

2. The cable television facsimile machine claim 1, wherein

the video signal has a vestigial chrominance upper side band and the frequency spectra of the modulated data carrier lies substantially within said vestigial side band.

3. The cable television facsimile machine of claim 1, the video signal having a horizontal scanning rate and the modulation means comprising:

a data carrier generator generating a data carrier at a quarter non-integral multiple of the horizontal scanning rate of the video signal; and

means for inhibiting the data carrier during the blanking intervals of the video signal.

4. The cable television facsimile machine of claim 3, further including a means for inserting a phase synchronization marker.

5. A facsimile machine for transmission of a facsimile image in a color video signal having a vestigial chrominance sideband and a horizontal scanning rate, the facsimile machine comprising:

means for scanning an image to obtain a digital representation of that image;

means responsive to the scanning means for modulating a data carrier based upon the digital representation to provide a modulated data signal; and

means for injecting the modulated data signal into the video signal, wherein

the modulation means generates a data carrier at a quarter non-integral multiple of the horizontal scanning rate of the video signal and inhibits the data carrier during the blanking intervals of the video signal.

6. The facsimile machine of claim 5, further including a means for inserting a phase synchronization marker.

7. The facsimile machine of claim 5, wherein the frequency spectra of the modulated data signal lies substantially within the vestigial chrominance sideband.

8. A method of transmitting an image in a color video signal having a bandwidth and a chrominance subcarrier, the method comprising:

scanning an image with a facsimile scanner to obtain a digital representation of that image;

modulating a data carrier based upon the digital representation of the image to provide a modulated signal; and

injecting the modulated signal into the video bandwidth at a frequency greater than the chrominance subcarrier.

9. The method of claim 8, the method further including inserting a phase synchronization marker.

10. The method of claim 8, the method further including modulating the data carrier at a quarter non-integral multiple of the horizontal scan rate of the video signal, the video signal having a horizontal scan rate.

11. A method of transmitting a facsimile image in a color video signal having a vestigial chrominance sideband and a horizontal scanning rate, the method comprising:

scanning an image to obtain a digital representation of that image;

modulating a data carrier at a quarter non-integral multiple of the horizontal scanning rate based upon the digital representation to provide a modulated signal;

inhibiting the data carrier during blanking intervals; and

injecting the modulated signal into the video signal.

12. The method of claim 11, the method further including inserting a phase synchronization marker.

13. The method of claim 11, the method further including injecting the modulated signal into the video signal so that the modulated signal lies substantially within said vestigial sideband.

14. A facsimile machine for adding an image into a rasterized video signal having both an active video portion and blanking intervals and chrominance and luminance portions, the facsimile machine comprising:

means for scanning an image to obtain a digital representation of that image;

means responsive to the scanning means for modulating a data carrier based upon the digital representation to provide a modulated data signal;

a combiner to combine the modulated data signal with the video signal during part of the active video intervals to provide a combined signal; and

a controller to control the modulating means such that the modulating means provides an unmodulated carrier burst at the start of at least some of the active video intervals.

15. The facsimile machine of claim 14, wherein the frequency of the data carrier is an odd quarter non-integral multiple of the horizontal scan rate.

16. The facsimile machine of claim 14, wherein the chrominance portion of the video signal has been generated by the modulation of a chrominance subcarrier and wherein the frequency of the data carrier is greater than the frequency of the chrominance subcarrier.

17. The facsimile machine of claim 15, wherein the chrominance portion of the signal has been generated by the modulation of a chrominance carrier and wherein the frequencies in the video signal above the chrominance carrier are substantially attenuated.

18. The facsimile machine of claim 14, wherein the facsimile machine further includes:

a sync detector generating a composite sync signal marking each blanking and active video interval; and

a clock generator providing a system clock signal referenced to the data carrier; and

wherein the controller controls the output of the modulator to provide the modulated data only during the active intervals.

19. A facsimile machine for injecting an image into a video signal having an active video portion and blanking intervals, a horizontal scanning frequency and luminance and chrominance spectra, the chrominance spectra having an upper side band and a lower side band, the facsimile machine comprising:

means for scanning an image to obtain a digital representation of that image;

a video processor section including means for attenuating the upper side band of the chrominance spectra and outputting a partially attenuated video signal having blanking intervals;

a carrier generator for generating a carrier at a frequency in the upper side band;

a data signal section responsive to the digital representation of the image to produce a rasterized data signal having blanking intervals synchronized to the blanking intervals of the video signal;

means responsive to the data signal section means for modulating the carrier with the rasterized data signal to provide a modulated signal with the spectral energy almost completely within the attenuated sideband; and

an adder for injecting the modulated signal into the partially attenuated video signal at a relatively low level of injection.

20. The facsimile machine of claim 19, wherein the data signal section further includes means for inserting a specified phase synchronizer marker into the data signal for a predetermined portion of the data signal.

21. The facsimile machine of claim 19, wherein the data signal section bandlimits the data signal.

22. A facsimile machine for transmitting an image with a video signal having video blanking intervals of a certain period, the facsimile machine comprising:

means for scanning an image to obtain a digital representation of that image;

means for rasterizing the digital representation to provide a rasterized data signal having blanking intervals a predetermined interval longer than the video blanking intervals;

a data carrier generator; and

means for combining the video and the rasterized data signal with the data carrier such that each video blanking interval begins substantially at the same time as the data blanking intervals such that the combined signal includes an unmodulated data carrier burst during intervals other than during the blanking interval.

23. The facsimile machine of claim 22, wherein the video signal has an active video interval between blanking intervals, the data carrier generator generates a data carrier burst at the start of each active line interval, and the combined signal includes a carrier burst.

24. A method for transmitting a facsimile image in a rasterized video signal having both an active video portion and blanking intervals and chrominance and luminance portions, the chrominance portion having a chrominance subcarrier, the method comprising:

scanning an image to obtain a digital representation of that image;

modulating a data carrier based upon the digital representation to provide a modulated data signal;

combining the modulated data signal with the video signal during part of the active video intervals to provide a combined signal; and

controlling the modulating means such that the modulating means provides an unmodulated carrier burst at the start of at least some of the active video intervals.

25. The method of claim 24, further including generating the data carrier at an odd quarter non-integral multiple of the horizontal scan rate.

26. The method of claim 24, further including generating a data carrier at a frequency higher than the frequency of the chrominance subcarrier.

27. The method of claim 25, further including substantially attenuating the frequencies in the video signal above the chrominance carrier.

28. The method of claim 24, further including:

detecting syncs;

generating a composite sync signal marking each blanking and active video interval;

providing a system clock signal referenced to the data carrier; and

controlling the output of the modulator to provide the modulated data only during the active intervals.

29. A method for injecting a facsimile image into a video signal having an active video portion and blanking intervals, a horizontal scanning frequency and luminance and chrominance spectra, the chrominance spectra having an upper side band and a lower side band, the facsimile machine comprising:

scanning an image to obtain a digital representation of that image;

attenuating the upper side band of the chrominance spectra and outputting a partially attenuated video signal having blanking intervals;

generating a carrier at a frequency in the upper side band;

producing a rasterized signal responsive to the digital representation of the image having blanking intervals synchronized to the blanking intervals of the video signal;

modulating the carrier with the rasterized data signal to provide a modulated signal with the spectral energy almost completely within the attenuated sideband; and

injecting the modulated signal into the partially attenuated video signal at a relatively low level of injection.

30. The method of claim 29, further including inserting a specified phase synchronizer marker into the data signal for a predetermined portion of the data signal.

31. The method of claim 29, further including bandlimiting the data signal.

32. A method for transmitting a facsimile image with a video signal having video blanking intervals of a certain period and an active video between blanking intervals, the method comprising:

scanning an image to obtain a digital representation of that image;

rasterizing the digital representation to provide a rasterized data signal having blanking intervals a predetermined interval longer than the video blanking intervals;

generating data carrier; and

combining the video and the rasterized data signal with the data carrier such that each video blanking interval begins substantially at the same time as the data blanking intervals such that the combined signal includes an unmodulated data carrier burst during intervals other than during the blanking interval.

33. The method of claim 32, further including

generating a data carrier burst at the start of each active line interval;

and

including a carrier burst in the combined signal.