Method and apparatus for nesting secondary signals within a television signal

• US 5,808,689 A
• Filed: 09/05/1995
• Issued: 09/15/1998
• Est. Priority Date: 04/20/1994
• Status: Expired due to Fees

• Current Assignee: Shoot The Moon Products II LLC
• Original Assignee: Shoot The Moon Products II LLC
• Inventors: Small, David
• Primary Examiner(s): Burgess, Glenton B.
• Application Number:
  US08/523,848
• Time in Patent Office: 1,106 Days
• Field of Search: 348/482, 348/483, 348/484, 348/473, 348/485, 348/460-462, 348/434, 348/480, 348/481, 348/474-476
• US Class Current: 348/476
• CPC Class Codes: H04N 7/025 Systems for the transmission of digital non-picture data, e.g. of text during the active part of a television frame transmission of digital non-picture data during the vertical blanking interval only H04N7/088
• CPC Class Codes: H04N 7/04 Systems for the transmission of one television signal, i.e. both picture and sound, by a single carrier H04N7/084, H04N7/087 take precedence
• CPC Class Codes: H04N 7/08 Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band , e.g. by time division H04N7/007 takes precedence
• CPC Class Codes: H04N 7/084 with signal insertion during the horizontal blanking interval only
• CPC Class Codes: H04N 9/802 involving processing of the sound signal H04N9/806, H04N9/835 take precedence

Abstract

A method and apparatus is disclosed for encoding secondary signals, such as audio signals, within a television signal in a manner such that the signal may be either recorded on a video cassette or broadcast. The audio samples are encoded only on selected lines of each video frame which do not interfere with dedicated broadcast and cable lines and are not affected by head switching of a video cassette recorder. The audio samples are encoded only within an overscan portion of the selected lines such that the encoded samples do not interfere with other portions of the video signal. However, by encoding the samples within the overscan portion, the samples do not affect the displayed image. The secondary audio signal is sampled during equally spaced intervals throughout the video frame, then compressed and encoded only within selected horizontal lines. During decoding, the audio samples are decompressed and played back at the original sampling rate to provide audio playback.

Claims

1. A method of transmitting secondary information within a television signal that produces successive fields, each having a first plurality of scan lines within a respective field time, the method comprising:

selecting a second plurality of scan lines among said first plurality of scan lines of the television signal to be encoded with control information and the secondary information;

producing samples of the secondary information by sampling said secondary information at a predetermined rate;

for each field, encoding an active video region of said second plurality of scan lines with the control information and a plurality of said samples, said control information indicating that said plurality of said samples are present in said second plurality of scan lines, said plurality of samples being equal in number to said samples taken within the field time, said second plurality of scan lines being encoded with said samples at a temporally compressed rate within the active video region; and

transmitting said television signal containing said secondary information and said control information.

2. The method of claim 1 wherein the secondary information includes audio information.

3. The method of claim 1, wherein the selecting of the second plurality of scan lines includes

ascertaining scan lines of said first plurality of scan lines reserved for network or cable operations and head switching locations;

and

excluding said scan lines from said second plurality of scan lines selected.

4. The method of claim 1, wherein when said plurality of samples are encoded at said temporally compressed rate, a time spacing between each sample of said plurality of said samples is less than a time spacing between each sample of said plurality of said samples taken at said predetermined rate.

5. The method of claim 1 further comprising:

receiving said television signal containing said secondary information;

extracting said plurality of said samples from said second plurality of scan lines; and

temporally decompressing said plurality of said samples so that each of said plurality of said samples containing said secondary information are output at a rate generally equal to said predetermined rate and are separated by substantially equal spaced time intervals.

6. The method of claim 1, wherein said encoding includes (i) ascertaining an overscan portion of each active video region of said second plurality of scan lines and (ii) encoding said overscan portions of at least two of said second plurality of scan lines with said control information.

7. The method of claim 1, wherein the control information indicates whether an overscan portion of the active video region of the second plurality of scan lines is encoded with the secondary information.

8. The method of claim 1, wherein the control information indicates whether the secondary information contained in the overscan portion of the active video region is valid.

9. The method of claim 1, wherein the control information includes at least one control bit which indicates whether an overscan portion of the active video region of the second plurality of scan lines is encoded with the secondary information.

10. The method of claim 9, wherein the control information further includes at least one control bit which indicates whether the secondary information is valid and is capable of being subsequently retrieved through decoding.

11. A method of recovering secondary information encoded as a plurality of samples within a television signal that produces successive fields, each having a first plurality of scan lines within a respective field time, said method comprising:

receiving said television signal containing said secondary information; and

for each field,

selecting a second plurality of scan lines among said first plurality of scan lines, said second plurality of scan lines being associated with a visible image of that field,

decoding an active video region of said second plurality of scan lines to obtain control information, and

examining said control information to identify whether the active video region further includes said plurality of samples.

12. The method of claim 11, wherein said decoding of said active video region includes extracting said control information and plurality of samples from an overscan portion of said active video region.

13. The method of claim 11, wherein said television signal is obtained from a broadcast.

14. The method of claim 11, wherein said television signal is obtained from a video cassette recorder.

15. The method of claim 11 further comprising:

decoding said active video region of said second plurality of scan lines to retrieve said plurality of samples; and

successively outputting at a uniform rate throughout the entire respective frame time, said extracted samples equal in number to said plurality of samples, whereby samples of secondary information placed in part of the encoded television signal associated with each frame are recovered and output at said uniform rate for each frame time and frame to frame.

16. The method of claim 15, wherein prior to successively outputting said extracted samples, the method further comprising examining the control information to determine whether the secondary information in the active video region of the encoded television signal is valid.

17. The method of claim 11 further comprising examining said control information to identify whether the secondary information is valid.

18. The method of claim 11, wherein the control information includes at least one control bit to indicate whether an overscan portion of the active video region of the second plurality of scan lines is encoded with the secondary information.

19. The method of claim 18, wherein the control information further includes at least one control bit which indicates whether the secondary information is valid and is capable of being subsequently retrieved.

21. The method of claim 15, wherein successively outputting said extracted samples is performed so that said extracted samples are output in a continuous manner and are at substantially equally spaced time intervals from each other.

20. In a video cassette prerecorded with an information signal including video information and secondary information encoded in a format such that a video cassette recorder transmits the information signal to display successive frames of a video image, including an overscan portion not visible from a properly calibrated monitor device, every respective frame time, the information signal associated with the display of each frame comprising:

a first segment including vertical blanking signals; and

a second segment including (i) horizontal blanking signals, (ii) control signals contained within a part of the information signal associated with the overscan portion to indicate whether the information signal provides valid information, and (iii) video signals which produce a displayed portion of the video image, wherein the information signal is encoded with said control signals and is encoded with a plurality of samples of the secondary information, equal in number to samples of the secondary information taken within the respective frame time.

22. An apparatus for encoding secondary information within a television signal that produces successive fields having a first plurality of lines, said apparatus comprising:

a first terminal for receiving said secondary information;

a second terminal for receiving said television signal;

means for generating a plurality of samples from said secondary information at a predetermined rate;

means for selecting a second plurality of lines among said first plurality of lines, said second plurality of lines excludes lines reserved for broadcast and cable operators or as head-switching locations; and

means for encoding a portion of the television signal that is associated with said second plurality of lines with said plurality of samples and for encoding the portion of the television signal with control information to at least indicate a presence of said plurality of samples.

23. The apparatus of claim 22, wherein said means for encoding includes means for compressing said plurality of samples to be stored with the portion of the television signal that represents an overscan portion of said second plurality of lines.

24. The apparatus of claim 22, wherein the portion of the television signal is encoded with said plurality of samples by said encoding means, said plurality of samples to be spaced non-equidistant from each other and within overscan portions of said second plurality of lines.

25. The apparatus of claim 22, wherein the secondary information is audio information.

26. The apparatus of claim 22, wherein said means for selecting includes a timing control circuit.

27. The apparatus of claim 22, wherein said means for generating includes

a timing and control circuit;

a sample and hold gate coupled to and controlled by said timing and control circuit, said sample and hold gate transfers said plurality of samples of the secondary information to said means for encoding; and

a sample and hold circuit coupled to said sample and hold gate, said sample and hold circuit temporarily delays transmission to said means for encoding of each sample of said plurality of samples.

28. The apparatus of claim 22, wherein said means for encoding includes

a timing and control circuit;

a synchronization separation and DC restoration circuit coupled to said second terminal and said timing and control circuit, said synchronization separation and DC restoration circuit outputs a composite synchronization signal to said timing and control circuit and a video signal;

an analog-to-digital converter coupled to said means for generating, and controlled by said timing and control circuit, said analog-to-digital converter converts said sample into a digital sample;

a storage element coupled to said analog-to-digital converter and controlled by said timing and control circuit, said storage element contains said digital sample;

a digital-to-analog converter coupled to said storage element and controlled by the first circuit, said digital-to-analog converter converts said digital sample into an analog sample;

a video gate coupled to said synchronization separation and DC restoration circuit and controlled by said timing and control circuit, said video gate outputs said video signal;

an audio gate coupled to said digital-to-analog converter and controlled by said timing control circuit to be active only when said video gate is inactivated by the timing and control circuit, said audio gate outputs said analog sample to be contained in the portion of the television signal being an overscan portion; and

at least one data gate coupled to the timing and control circuit, the at least one data gate places the control information, indicating whether said audio sample is present in said overscan portion and is valid, into at least one scan line of the second plurality of lines when activated by the timing and control circuit.

29. The apparatus of claim 22 further comprising

an amplifier coupled to said first terminal, said amplifier amplifies at least said secondary information before sampled by said means for generating.

30. An apparatus for retrieving control information and secondary information encoded at a first rate as a plurality of samples within a television signal that produces successive video fields having a first plurality of lines, said apparatus comprising:

a terminal for receiving said television signal containing said secondary information;

means for selecting a second plurality of lines among said first plurality of lines;

means for decoding an overscan portion of at least two lines of said second plurality of lines in order to retrieve the control information used to identify whether the secondary information, from which said plurality of samples were formed, is present and is valid;

means for extracting said plurality of samples from the overscan portion of said second plurality of lines; and

means for temporally decompressing said plurality of samples by outputting each of said plurality of samples at a second rate slower than the first rate and at substantially equally spaced time intervals in order to produce a continuous output of secondary information.

31. The apparatus of claim 30, wherein said means for decompressing said plurality of samples includes means for outputting said plurality of samples at substantially equally spaced time intervals;

wherein each of said second plurality of lines has an active video region, and each of said active video regions includes an overscan portion;

wherein said plurality of samples and said control information are extracted from said overscan portions of said second plurality of lines; and

wherein said second plurality of lines includes only usable lines and not unusable lines.

32. An apparatus for encoding secondary information within a television signal that produces a video frame having a first plurality of lines, said apparatus comprising:

a first terminal to receive secondary information;

a second terminal to receive a television signal having a second plurality of lines of said first plurality of lines that represent a visible image of the video frame;

a timing and control circuit to control encoding of an active region of said second plurality of lines with said secondary information and with control information;

a storage element coupled to said timing circuit;

a sampling and digitizing circuit coupled to said first terminal and said timing and control circuit, said sampling and digitizing circuit storing samples of said secondary information at a first rate;

an audio gate coupled to said storage element and said timing and control circuit, said audio gate is activated by said timing and control gate to allow an overscan portion of said second plurality of lines of said television signal to be encoded with said samples of said secondary information at a temporally compressed rate faster than said first rate; and

at least one data gate coupled to said timing and control circuit, said at least one data gate is activated by said timing and control circuit to encode an overscan portion of at least one of said second plurality of lines with the control information used to indicate at least whether the secondary information is valid.