Filter by-pass for transmitting an additional signal with a video signal

• US 5,617,148 A
• Filed: 03/31/1995
• Issued: 04/01/1997
• Est. Priority Date: 06/14/1991
• Status: Expired due to Fees

• Current Assignee: WAVO Corporation
• Original Assignee: WavePhore, Inc.
• Inventors: Montgomery, Gerald D.
• Primary Examiner(s): Metjahic, Safet
• Application Number:
  US08/415,163
• Time in Patent Office: 732 Days
• Field of Search: 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, 348/434, 348/435, 370/69.1, 370/123, 370/76.57, 370/121
• US Class Current: 348/473
• CPC Class Codes: H04N 5/445 for displaying additional information H04N5/50 takes precedence
• CPC Class Codes: H04N 7/035 Circuits for the digital non-picture data signal, e.g. for slicing of the data signal, for regeneration of the data-clock signal, for error detection or correction of the data signal
• 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

A controlled element for spectrum attenuation or a controlled filter is disclosed that is used to aid in the insertion of a secondary signal into a video signal without distorting the blanking intervals or close captioned data contained in the blanking interval of the video signal.

Claims

1. In a processor for injecting a second signal into a primary video signal for subsequent transmission having a power spectrum and blanking intervals separating active video lines, the processor comprising:

a blanking interval detector responsive to the primary video signal;

a controllable element responsive to the video signal and the blanking interval detector and providing at an output an output video signal having at least one substantially attenuated portion of the power spectrum during at least some portions of the active video lines and leaving the same portion of the power signal spectrum substantially unattenuated during at least some of the blanking intervals; and

a secondary section injecting the second signal into the output of the controllable element.

2. The processor of claim 1, wherein the blanking intervals are the horizontal blanking intervals.

3. In a processor for injecting a second signal into a primary video signal for subsequent transmission having a power spectrum and blanking intervals separating active video lines, the processor comprising:

a blanking interval detector responsive to the primary video signal; and

a controllable element responsive to the video signal and the blanking interval detector and providing at an output an output video signal having at least one substantially attenuated portion of the power spectrum during at least some portions of the active video lines and leaving the same portion of the power signal spectrum substantially unattenuated during at least some of the blanking intervals;

wherein the controllable element is also responsive to a manual control to leave said same portion substantially unattenuated to thereby further facilitate the testing of a transmission link.

4. The processor of claim 3, wherein the blanking intervals are the horizontal blanking intervals.

5. In a processor for injecting a second signal into a primary video signal for subsequent transmission having a power spectrum and blanking intervals separating active video lines, the processor comprising:

a blanking interval detector responsive to the primary video signal; and

a controllable element responsive to the video signal and the blanking interval detector and providing at an output an output video signal having at least one substantially attenuated portion of the power spectrum during at least some portions of the active video lines and leaving the same portion of the power signal spectrum substantially unattenuated during at least some of the blanking intervals;

wherein the processor includes a secondary signal section responsive to the second signal further providing an absence signal indicating the absence of a second signal; and

the controllable element is responsive to the absence signal such that no attenuation occurs in response to the absence signal.

6. The processor of claim 5, wherein the blanking intervals are the horizontal blanking intervals.

7. In a processor for injecting a second signal into a primary video signal for subsequent transmission having a power spectrum and blanking intervals separating active video lines, the processor comprising:

a blanking interval detector responsive to the primary video signal; and

a controllable element responsive to the video signal and the blanking interval detector and providing at an output an output video signal having at least one substantially attenuated portion of the power spectrum during at least some portions of the active video lines and leaving the same portion of the power signal spectrum substantially unattenuated during at least some of the blanking intervals;

wherein the controllable element comprises a filter responsive to the primary video signal and a controllable switch coupled to by-pass the filter during the blanking intervals so that the filter has no effect on the primary video signal.

8. The processor of claim 7, wherein the blanking intervals are the horizontal blanking intervals.

9. In a processor for injecting a second signal into a primary video signal for subsequent transmission having a power spectrum and blanking intervals separating active video lines, the processor comprising:

a blanking interval detector responsive to the primary video signal; and

a controllable element responsive to the video signal and the blanking interval detector and providing at an output an output video signal having at least one substantially attenuated portion of the power spectrum during at least some portions of the active video lines and leaving the same portion of the power signal spectrum substantially unattenuated during at least some of the blanking intervals;

wherein the controllable element comprises a filter having an input and an output responsive to the primary video signal and an alterable impedance path providing a low impedance by-pass between the input and out output of the filter to thereby by-pass the filter during the blanking intervals.

10. The processor of claim 9, wherein the blanking intervals are the horizontal blanking intervals.

11. A method of combining a first video signal having a frequency spectrum and blanking intervals separating active video lines including a second signal present during only a part of at least some blanking intervals with a third signal, the method comprising:

attenuating a portion of the spectrum of the combined signal during some time intervals when the second signal is not present; and

injecting the third signal into the first signal when the second signal is not present;

wherein attenuation is accomplished by a filter filtering the first video signal and wherein the method further includes bypassing the filter during said time intervals when the first signal is present.

12. The processor of claim 11, wherein the time intervals are the horizontal blanking intervals.

13. A method of injecting a second signal into a rasterized primary video signal having blanking intervals separating active video lines, the video signal having luminance and chrominance information and a chrominance subcarrier, the method comprising:

detecting the blanking intervals of the video signal;

substantially attenuating a portion of the video signal during at least part of some active video lines;

injecting the secondary signal into the portions of the video lines that are attenuated; and

passing the blanking interval portions of the video signal without attenuating said portion of the video signal and without injecting the second signal;

wherein the attenuating is done by a filter that is by-passed during the blanking intervals.

14. In a processor for injecting a second signal into a primary video signal for subsequent transmission having a power spectrum and blanking intervals separating active video lines, the processor comprising:

a blanking interval detector responsive to the primary video signal; and

a controllable element responsive to the video signal and the blanking interval detector and providing an output an output video signal having at least one substantially attenuated portion of the power spectrum during at least some portions of the active video lines and leaving the same portion of the power signal spectrum substantially unattenuated during at least some of the blanking intervals;

wherein the blanking detector further detects a predetermined interval in at least one field in a frame and the controllable element provides substantially no attenuation during the predetermined interval;

wherein the blanking intervals are the horizontal blanking intervals.