Process for precisely identifying a desired location on a video tape

• US 5,917,990 A
• Filed: 04/22/1998
• Issued: 06/29/1999
• Est. Priority Date: 04/22/1998
• Status: Expired due to Fees

• Current Assignee: Pinnacle Systems Incorporated (Avid Technology Incorporated)
• Original Assignee: Pinnacle Systems Incorporated (Avid Technology Incorporated)
• Inventors: Zamara, Christopher J., Maltz, Ivan J.
• Primary Examiner(s): NGUYEN, HUY THANH
• Application Number:
  US09/064,677
• Time in Patent Office: 433 Days
• Field of Search: 386/46, 386/95, 386/121, 386/111, 386/68, 386/81, 386/65, 386/52, 386/83
• US Class Current: 386/239
• CPC Class Codes: G11B 2220/90 Tape-like record carriers
• CPC Class Codes: G11B 27/032 on tapes G11B27/036, G11B27/038 take precedence
• CPC Class Codes: G11B 27/107 of operating tapes
• CPC Class Codes: G11B 27/28 by using information signals recorded by the same method as the main recording G11B27/22 takes precedence
• CPC Class Codes: H04N 5/147 Scene change detection

Abstract

A process that allows precise control of the tape position in consumer videotape devices, such as camcorders, for the purpose of video editing. The process involves the use of a software algorithm within the central processing unit of a computer to locate a specific video frame with digitized video. The process first involves storing an initial set of calculated scene detection data, including luminance and change of luminance values for each video frame. Then, at the time of the video editing, a second set of scene detection data from the videotape is taken at a reference point, near the location of the desired frame. The second set of scene detection data is compared to the first set of scene detection data to determine whether there is any offset between the expected location of the frame, as shown in the first set of scene detection data, and the actual location of the desired frame, as shown in the second set of scene detection data. If there is any offset, the videotape can then be adjusted by the determined amount of offset to locate the desired frame.

Claims

1. A process for precisely identifying a desired location on a linear storage medium, particularly a magnetic tape, comprising:

storing a first set of calculated scene detection data from each of a set of video frames on the tape;

scanning the scene detection data to find a point of interest near the desired location;

locating a reference point on the tape near the desired location, the reference point being prior to the point of interest;

storing a second set of scene detection data from a set of video frames located around the reference point for a first number of samples;

comparing the first and second sets of scene detection data to determine an offset; and

adjusting the tape to the desired location using the determined offset.

2. The process of claim 1 wherein comparing the first and second sets of scene detection data includes comparing a second number of samples around the point of interest from the first set of scene detection data to first number of samples of the second set of scene detection data.

3. The process of claim 2 wherein the first number of samples is greater than the second number of samples.

4. The process of claim 1 wherein the first and second sets of scene detection data include a value for an overall average luminance of the video frame and a value for an average difference of pixel-by-pixel luminance between the video frame and an immediately prior video frame.

5. The process of claim 1 wherein locating a reference point comprises:

resetting the tape, such that a starting position on the tape corresponds to a zero position on a tape counter;

sending an appropriate tape transport command;

reading the tape counter of a videotape device to determine a position near the reference point;

engaging a play mode; and

waiting until the tape counter shows the reference point.

6. The process of claim 1 wherein locating a reference point involves the use of an infrared-controlled camcorder.

7. The process of claim 4 wherein scanning the scene detection data to find a point of interest further comprises:

examining the average luminance and average difference values for each video frame; and

stopping the examination when an unusually high average difference value and an unusually high change in the average luminance value is found.

8. The process of claim 2 wherein a matching algorithm is used to compare the second set of scene detection data to the first set of scene detection data.

9. A process for precisely identifying a desired location on a linear storage medium, particularly a magnetic tape, comprising:

storing a first set of calculated scene detection data from each of a set of video frames on the tape;

scanning the scene detection data to find a point of interest near the desired location;

searching the tape for a reference point the reference point being prior to the point of interest;

playing the tape from the reference point and storing a second set of scene detection data for a first number of samples;

comparing a second number of samples around the point of interest from the first set of scene detection data to the second set of scene detection data to determine an alignment position;

determining an offset from the alignment position of the first set of scene detection data and the second set of scene detection data; and

adjusting the tape by the determined offset to find the desired location on the tape.

10. The process of claim 9 wherein the first number of samples is greater than the second number of samples.

11. The process of claim 10 wherein the first and second sets of scene detection data include a value for an overall average luminance of the video frame and a value for an average difference of pixel-by-pixel luminance between the video frame and an immediately prior video frame.

12. The process of claim 11 wherein scanning the scene detection data to find a point of interest further comprises:

examining the average luminance and average difference values for each video frame; and

stopping the examination when an unusually high average difference value and an unusually high change in the average luminance value is found.

13. The process of claim 9 wherein searching the tape for a reference point further comprises:

resetting the tape, such that a starting position on the tape corresponds to a zero position on a tape counter;

sending an appropriate tape transport command;

reading the tape counter of a videotape device to determine a position near the reference point;

engaging a play mode; and

waiting until the tape counter shows the reference point.

14. The process of claim 9 wherein searching the tape for a reference point involves the use of an infrared-controlled camcorder.

15. The process of claim 9 wherein comparing the first set of scene detection data to the second set of scene detection data to determine an alignment position is accomplished by using a matching algorithm.

16. A process for precisely identifying a desired location on a linear storage medium, particularly a magnetic tape, comprising:

calculating and storing a first set of scene detection data from each of a set of video frames on the tape;

scanning the first set of scene detection data to find a point of interest near the desired location, the point of interest being at a location on the tape where the scene detection data is characterized by unusual localized changes;

searching the tape for a reference point near the desired location, the reference point being located prior to the point of interest;

playing the tape from the reference point and storing a second set of scene detection data for a first number of samples;

comparing a second number of samples around the point of interest from the first set of scene detection data to the second set of scene detection data by use of a matching algorithm to determine an alignment position;

determining an offset from the alignment position of the first set of scene detection data and the second set of same detection data; and

adjusting the tape by the determined offset to find the desired location on the tape.

17. The process of claim 16 wherein the first and second sets of scene detection data include a value for an overall average luminance of the video frame and a value for an average difference of pixel-by-pixel luminance between the video frame and an immediately prior video frame.

18. The process of claim 17 wherein scanning the scene detection data to find a point of interest further comprises:

examining the average luminance and average difference values for each video frame; and

stopping the examination when an unusually high average difference value and a unusually high change in the average luminance value is found.

19. The process of claim 16 wherein searching the tape for a reference point further comprises:

resetting the tape, such that a starting position on the tape corresponds to a zero position on a tape counter;

sending an appropriate tape transport command;

reading the tape counter of a videotape device to determine a position near the reference point;

engaging a play mode; and

waiting until the tape counter shows the reference point.

20. The process of claim 16 wherein searching the tape for a reference point involves the use of an infrared-controlled camcorder.