Encoding and decoding of embedded data stream in analog video using copy protection pulses
View Patent ↗Method and apparatus for encoding and decoding a stream of digital (binary) data on AGC (automatic gain control) pulses or back porch pulses of the type conventionally used for copy protection in the analog television or video realm. The data is encoded onto the tips of the AGC or back porch pulses added to blanking intervals of an analog video signal. Each pulse tip may define, for instance, 10 to 15 digital bits (1 or 0) in the form of square waves or rectangular waves with two states, high and low, representing respectively 1 and 0. In another version, the digital data is similarly encoded onto the pulse tip of back porch pulses present at the end of video fields for copy protection. This digital data conveyed in an analog signal may be read by an associated decoder in a consumer device and the resulting data decoded, for instance, for copy control, storage permission, network access, user identification, or carrying additional data, such as commentary or text relevant to the accompanying video. The data bandwidth here is substantial since each AGC or back porch pulse may carry, for instance, 15 bits of digital data and the AGC or back porch pulses may be present in each of the horizontal and vertical blanking intervals of a video signal.
1. A method comprising the acts of:
providing digital data;
providing a video signal;
providing in the video signal in blanking intervals thereof, and following a horizontal synchronization pulse, pulses of a type to inhibit subsequent analog video recording of the video signal; and
encoding the digital data onto an extremity of at least one of the provided pulses.
2. The method of claim 1 , wherein the blanking interval is a horizontal blanking interval or a vertical blanking interval.
3. The method of claim 1 , wherein the encoded digital data does not substantially reduce the inhibition of subsequent analog video recording.
4. The method of claim 1 , wherein each pulse extremity accommodates at least 10 bits of the digital data.
5. The method of claim 1 , wherein each bit of the encoded digital data has a duration in the range of 1/10 to ⅓ μ sec.
6. The method of claim 1 , wherein each bit of the encoded digital data has an amplitude in the range of 25 mV to 125 mV.
7. The method of claim 1 , wherein the provided pulses are positive-going with respect to the negative-going horizontal synchronization pulse.
8. The method of claim 1 , wherein the provided pulses are AGC or back porch pulses.
9. The method of claim 1 , wherein the encoded digital data carries information relating to one of copy protection, storage control, network access, entitlement, user identification, mobile device activation, or mobile device registration.
10. A method comprising the acts of:
receiving an analog video signal having in blanking intervals thereof, and following a horizontal synchronization pulse, pulses of a type to inhibit video recording of the video signal; and the extremity of at least one of the pulses carrying encoded digital data;
detecting the encoded digital data; and
decoding the detected digital data to form a digital data signal.
11. The method of claim 10 , wherein the blanking intervals are horizontal blanking intervals or vertical blanking intervals.
12. The method of claim 10 , wherein the encoded digital data does not substantially reduce the inhibition of subsequent analog video recording.
13. The method of claim 10 , wherein each pulse extremity accommodates at least 10 bits of the digital data.
14. The method of claim 10 , wherein each bit of the encoded digital data has a duration in the range of 1/10 to ⅓ μ sec.
15. The method of claim 10 , wherein each bit of the encoded digital data has an amplitude in the range of 25 mV to 125 mV.
16. The method of claim 10 , wherein the pulses are positive-going with respect to the negative-going horizontal synchronization pulse.
17. The method of claim 10 , wherein the pulses are AGC pulses or back porch pulses.
18. The method of claim 10 , wherein the encoded digital data carries information relating to one of copy protection, storage control, network access, entitlement, user identification, mobile device activation, or mobile device registration.
19. Apparatus for encoding digital data onto an analog video signal, comprising:
an input terminal for receiving a digital video signal;
an input terminal for receiving digital data;
a video encoder coupled to the input terminals to provide in the video signal in blanking intervals thereof, and following a horizontal synchronization pulse, pulses of a type to inhibit subsequent analog video recording of the video signal, and to encode the digital data into an extremity of at least one of the provided pulses;
a digital to analog converter coupled to the video encoder to convert the video signal to analog form; and
an output terminal coupled to the digital to analog converter.
20. Apparatus for decoding digital data carried on an analog video signal, comprising:
an input terminal for receiving an analog video signal;
an analog to digital converter coupled to the input terminal;
video processing circuitry coupled to the converter to output the video signal in digital form;
a decoder coupled to the converter and which detects in the converted video signal in blanking intervals thereof, and following a horizontal synchronization pulse, pulses of a type to inhibit video recording of the video signal, and wherein the decoder detects at the extremity of at least one of the detected pulses encoded digital data and decodes the detected digital data; and
an output terminal coupled to the decoder and which outputs the decoded digital data as a digital data signal.