Method and apparatus for copy protection detection in a video signal

• US 7,603,025 B2
• Filed: 12/09/2003
• Issued: 10/13/2009
• Est. Priority Date: 05/21/1999
• Status: Expired due to Fees

• Current Assignee: ATI Technologies ULC (Advanced Micro Devices, Inc.)
• Original Assignee: ATI Technologies ULC (Advanced Micro Devices, Inc.)
• Inventors: Rinaldi, Antonio
• Primary Examiner(s): Tran; Thai
• Assistant Examiner(s): Hasan; Syed Y
• Application Number:
  US10/731,217
• Publication Number:
  US 20040114907A1
• Time in Patent Office: 2,135 Days
• Field of Search: 386/94, 386/E5.004, 348/465, 348/545, 360/60, 380/201
• US Class Current: 386/252
• CPC Class Codes: H04N 2005/91314 the copy protection signal being a pulse signal inserted in blanking intervals of the video signal, e.g. pseudo-AGC pulses, pseudo-sync pulses
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection

Abstract

A method and apparatus for detecting copy protection included in an input video signal is described. Two types of copy protection are particularly addressed, including techniques that imbed copy protection pulses and copy protection phase flips in the video signal. A method for preserving copy protection is also presented, where the input video signal is first examined to determine if copy protection has been included in the input video signal. The input video signal then converted to component video data, which removes any copy protection present. An output video signal is then generated from the component video data, and when it was determined that the input video signal includes copy protection, the copy protection is recreated in the output video signal.

Claims

1. A copy protection pulse detection circuit, comprising:

a pulse detector, wherein the pulse detector receives an input video signal and sets a pulse detect indication each time a pulse that exceeds a first threshold is detected in the input video signal;

an accumulator operably coupled to the pulse detector, wherein the accumulator counts a number of pulses received in each field of the input video signal to produce an accumulated count;

a field pulse comparator operably coupled to the accumulator, wherein the field pulse comparator compares the accumulated count for each field with a second threshold, wherein when the accumulated count exceeds the second threshold for a field, the field pulse comparator asserts a positive count indication for the field;

a decision counter operably coupled to the field pulse comparator, wherein the decision counter increments a decision count when the positive count indication is asserted for a field and decrements the decision count when the positive count indication is not asserted for a field; and

a decision comparator operably coupled to the decision counter, wherein when the decision count reaches a high threshold, the decision comparator sets a pulses detected indication, wherein when the decision count reaches a low threshold, the decision comparator clears the pulses detected indication.

2. The copy protection pulse detection circuit of claim 1, wherein the pulse detector further comprises:

an analog to digital converter that converts the input video signal to a digital input signal;

a low pass filter operably coupled to the analog to digital converter, wherein the low pass filter filters the digital input signal to produce a filtered input signal; and

a pulse detection comparator operably coupled to the low pass filter, wherein the pulse detection comparator compares digital values in the filtered input signal with the first threshold, wherein the pulse detection comparator sets the pulse detect indication each time a digital value exceeds the first threshold.

3. The copy protection pulse detection circuit of claim 2, wherein the pulse detector further comprises a blanking interval gate, operably coupled to the pulse detection comparator, wherein the blanking interval gate selectively passes the pulse detect indication based on a received signal indicating that the input video signal is in the vertical blanking interval.

4. The copy protection pulse detection circuit of claim 3, wherein the detection circuit is included on a video graphics integrated circuit.