Image signal processor for detecting duplicate fields

• US 6,469,745 B1
• Filed: 09/02/1998
• Issued: 10/22/2002
• Est. Priority Date: 09/04/1997
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Yamada, Yoshihisa, Murakami, Tokumichi, Kato, Yoshiaki
• Primary Examiner(s): Miller, John
• Assistant Examiner(s): Natnael, Paulos
• Application Number:
  US09/145,887
• Time in Patent Office: 1,511 Days
• Field of Search: 348/526, 348/459, 348/700, 348/443, 348/452, 348/384, 348/570, 348/622, 348/666, 348/401.1, 348/558
• US Class Current: 348/558
• CPC Class Codes: H04N 7/0112 one of the standards corresponding to a cinematograph film standard

Abstract

An image signal processor is provided which accurately detects duplicate fields of a telecinema signal. The image signal processor includes a duplicate field detecting means for detecting duplicate fields of the telecinema signal and a duplicate field removing means for removing the duplicate fields. The duplicate field detecting means uses a threshold value for detecting a duplicate field and a threshold value for detecting a non-duplicate field to improve the accuracy of detection.

Claims

1. An image signal processor, comprising:

a duplicate field detecting means for detecting a duplicate field of an image signal, said duplicate field detecting means determining whether a current field is a duplicate field by comparing a cumulative value of the current field with a first threshold value for detecting a duplicate field, comparing said cumulative value for said current field of said image signal with said first threshold value and detecting said current field as a non-duplicate field when the cumulative value for said current field is greater than said first threshold value and comparing a cumulative value of each of a plurality of fields preceding said current field with a second threshold value for detecting a non-duplicate field different from said first threshold value; and

a duplicate field removing means for removing said duplicate field detected by said duplicate field detecting means.

2. The image signal processor according to claim 1, wherein said duplicate field detecting means comprises:

a subtracting means for obtaining a plurality of field differential values by comparing a plurality of first fields of said image signal and comparing a plurality of second fields of said image signal; and

a duplicate field determining means for determining duplicate fields according to a pattern of appearance of duplicate and non-duplicate fields.

3. The image signal processor according to claim 2, wherein said duplicate field detecting means adjusts said threshold value for detecting a duplicate field based on a periodicity of said duplicate fields detected by said duplicate field determining means.

4. The image signal processor according to claim 3, further comprising:

a memory for storing a plurality of results of detection made by said duplicate field determining means,

wherein said duplicate field determining means decreases said threshold value for detecting a duplicate field when a pattern of appearance of duplicate and non-duplicate fields does not correspond with a predetermined pattern of appearance of duplicate and non-duplicate fields.

5. The image signal processor according to claim 4, wherein said duplicate field determining means increases said threshold value for detecting a duplicate field when a pattern of appearance of duplicate and non-duplicate fields corresponds with said predetermined pattern.

6. The image signal processor according to claim 2, wherein said duplicate field detecting means further comprises:

an absolutizing means for obtaining a plurality of absolute values by absolutizing said field differential values; and

a one-field cumulative adder means for obtaining a plurality of cumulative values by accumulating said absolute values, wherein each of said cumulative values relates to one of said first fields and said second fields, wherein

said duplicate field determining means determines said duplicate field by comparing one of said cumulative values, which is said cumulative value of the current field, with said first threshold value for detecting a duplicate field and comparing the other cumulative values, which are cumulative values for said plurality of fields preceding said current field, with said second threshold value for detecting a non-duplicate field respectively.

7. The image signal processor according to claim 6, wherein said duplicate field detecting means further comprises:

a threshold value determining means for determining said second threshold value for detecting a non-duplicate field based on said one of said cumulative values.

8. The image signal processor according to claim 7, wherein said threshold value determining means determines said second threshold value for detecting a duplicate field such that said second threshold value is in direct said second fields.

9. The image signal processor according to claim 6, wherein

said duplicate field determining means determines that said current field is a duplicate field when the cumulative value of each of said plurality of fields is greater than said second threshold value for detecting a non-duplicate field, the cumulative values of said plurality of fields relating to a predetermined number of fields which adjacently antecede said current field, said predetermined number being determined based on a field rate of a movie film and a field rate of said image signal.

10. The image signal processor according to claim 9, wherein said image signal is telecinema signal of 30 Hz produced from a movie film of 24 Hz, and said duplicate field determining means further comprises:

a memory for storing said cumulative values;

a means for determining that said current field is potentially a duplicate field by detecting that the cumulative value of said current field is smaller than said first threshold value for detecting a duplicate field; and

a means for detecting that said potentially duplicate field is a duplicate field by detecting that four consecutive cumulative values are greater than said second threshold value for detecting a non-duplicate field, wherein said four consecutive cumulative values are for fields adjacent to said potentially duplicate field.

11. The image signal processor according to claim 2, wherein said duplicate field detecting means detects duplicate fields based on said image signal relating to partial data of a first field.

12. The image signal processor according to claim 2, said duplicate field detecting means further comprising:

a field memory storing two fields of said image signal and outputting said image signal to said subtracting means;

an absolutizing means for obtaining a plurality of absolute values by absolutizing said field differential values obtained by said subtracting means;

a one-field cumulative adder means for obtaining a plurality of cumulative values by accumulating absolute values, wherein each of said cumulative values relates to one of said first fields and said second fields;

a cumulative value memory for storing said cumulative values;

a threshold value memory storing said threshold value for detecting a duplicate field; and

a threshold value determining means for determining said threshold value for detecting a non-duplicate field based on one of said cumulative values, wherein

said duplicate field determining means is operatively connected to said one-field cumulative adder means, said cumulative value memory, said threshold value memory, and said threshold value determining means, and determines said duplicate field by checking said pattern of appearance of duplicate and non-duplicate fields based on said first threshold value for detecting a duplicate field, said second threshold value for detecting a non-duplicate field, and said plurality of field differential values.

13. The image signal processor according to claim 2, wherein said duplicate field removing means removes one of said plurality of first fields which temporally antecedes and corresponds to a duplicate field detected by said duplicate field detecting means when said detected duplicate field corresponds to said plurality of first fields, and removes said detected duplicate field when said detected duplicate field corresponds to said plurality of second fields.

14. An image signal processor, comprising:

a logic circuit that outputs a series of cumulative values, each cumulative value representing a difference between temporally offset fields of an image signal; and

a microprocessor that detects whether a current field is a duplicate field by

(i) comparing a cumulative value for said current field and a threshold value for detecting a duplicate field, and

(ii) comparing said cumulative value for said current field of said image signal with said first threshold value and detecting said current field as a non-duplicate field when the cumulative value for said current field is greater than said first threshold value and comparing a cumulative value for each of a plurality of fields that immediately precede said current field and a second threshold value for detecting a non-duplicate field when said cumulative value for said current field is less than said first threshold value.

15. The image signal processor according to claim 14, wherein each cumulative value represents a cumulative added absolute value of the difference between temporally offset fields.

16. The image signal processor according to claim 14, wherein said microprocessor determines duplicate fields based on periodic appearance of duplicate fields.

17. The image signal processor according to claim 14, wherein said threshold value for detecting a non-duplicate field is based on the cumulative value for said current field when the cumulative value for said current field is lower than said threshold value for detecting a duplicate field.

18. An image signal processing method, comprising:

outputting a series of cumulative values, each cumulative value representing a difference between temporally offset fields of an image signal; and

detecting whether a current field is a duplicate field by

(i) comparing a cumulative value for said current field and a threshold value for detecting a duplicate field, and

(ii) comparing said cumulative value for said current field of said image signal with said first threshold value and detecting said current field as a non-duplicate field when the cumulative value for said current field is greater than said first threshold value and comparing a cumulative value for each of a plurality of fields that immediately precede said current field and a second threshold value for detecting a non-duplicate field when said cumulative value for said current field is less than said first threshold value.

19. The image signal processing method according to claim 18, wherein said outputting step includes calculating each cumulative value by cumulatively adding absolute values of the difference between temporally offset fields.

20. The image signal processing method according to claim 18, further comprising:

determining duplicate fields based on periodic appearance of duplicate fields.

25. The image signal processing method according to claim 18, wherein said step of detecting whether a current field is a duplicate field determines that said current field is a non-duplicate field when the cumulative value for said current field is greater than said threshold for detecting a duplicate field and determines that said current field is a duplicate field when the cumulative value for said current field is less than said threshold for detecting a duplicate field and the cumulative values for said plurality of fields that immediately precede said current field are each greater than said threshold for detecting a non-duplicate field.

26. The image signal processing method according to claim 18, wherein the number of fields immediately preceding said current field is four.

27. The image signal processing method according to claim 18, wherein said step of detecting whether a field is a duplicate field determines that said current field is a non-duplicate field when the cumulative value of one of said plurality of fields that immediately precede said current field is less than said threshold for detecting a non-duplicate field.

21. The image signal processor comprising:

a duplicate field detecting means for detecting a duplicate field of an image signal, said duplicate field detecting means determining whether a current field is a duplicate field by comparing a cumulative value of the current field with a first threshold value for detecting a duplicate field, and comparing a cumulative value of each of a plurality of fields preceding said current field with a second threshold value for detecting a non-duplicate field different from said first threshold value; and

a duplicate field removing means for removing said duplicate field detected by said duplicate field detecting means, wherein said duplicate field detecting means performs the functions of;

comparing said cumulative value for said current field of said image signal with said first threshold value and detecting said current field as a non-duplicate field when the cumulative value for said current field is greater than said first threshold value; and

comparing said cumulative value for each of the plurality of fields preceding said current field with said second threshold when said cumulative value for said current field is less than said first threshold value.

22. The image signal processor according to claim 21, wherein said duplicate field detecting means detects said current field as a non-duplicate field when the cumulative value for a previous field of said plurality of fields preceding said current field is less than said second threshold value.

23. The image signal processor according to claim 21, wherein said duplicate field detecting means detects said current field as a duplicate field when the cumulative value for each of said plurality of fields preceding said current field is greater than said second threshold value.

24. The image signal processor according to claim 23, wherein said duplicate field detecting means detects said current field as a duplicate field when the cumulative value for four consecutive previous fields is greater than said second threshold value.

29. The image signal processor according to claim 21, wherein said duplicate field detecting means comprises:

a subtracting means for obtaining a plurality of field differential values by comparing a plurality of first fields of said image signal and comparing a plurality of second fields of said image signal; and

a duplicate field determining means for determining duplicate fields according to a pattern of appearance of duplicate and non-duplicate fields.

30. The image signal processor according to claim 29, wherein said duplicate field detecting means adjusts said threshold value for detecting a duplicate field based on a periodicity of said duplicate fields detected by said duplicate field determining means.

31. The image signal processor according to claim 30, further comprising:

a memory for storing a plurality of results of detection made by said duplicate field determining means,

wherein said duplicate field determining means decreases said threshold value for detecting a duplicate field when a pattern of appearance of duplicate and non-duplicate fields does not correspond with a predetermined pattern of appearance of duplicate and non-duplicate fields.

32. The image signal processor according to claim 31, wherein said duplicate field determining means increases said threshold value for detecting a duplicate field when a pattern of appearance of duplicate and non-duplicate fields corresponds with said predetermined pattern.

33. The image signal processor according to claim 29, wherein said duplicate field detecting means further comprises:

an absolutizing means for obtaining a plurality of absolute values by absolutizing said field differential values; and

a one-field cumulative adder means for obtaining a plurality of cumulative values by accumulating said absolute values, wherein each of said cumulative values relates to one of said first fields and said second fields, wherein

said duplicate field determining means determines said duplicate field by comparing one of said cumulative values, which is said cumulative value of the current field, with said first threshold value for detecting a duplicate field and comparing the other cumulative values, which are cumulative values for said plurality of fields preceding said current field, with said second threshold value for detecting a non-duplicate field respectively.

34. The image signal processor according to claim 33, wherein said duplicate field detecting means further comprises:

a threshold value determining means for determining said second threshold value for detecting a non-duplicate field based on said one of said cumulative values.

35. The image signal processor according to claim 34, wherein said threshold level determining means determines said second threshold value for detecting a duplicate field such that said second threshold value is in direct proportion to said one of said cumulative values.

36. The image signal processor according to claim 33, wherein

said duplicate field determining means determines that said current field is a duplicate field when the cumulative value of each of said plurality of fields is greater than said second threshold value for detecting a non-duplicate field, the cumulative values of said plurality of fields relating to a predetermined number of fields which adjacently antecede said current field, said predetermined number being determined based on a field rate of a movie film and a field rate of said image signal.

37. The image signal processor according to claim 36, wherein said image signal is telecinema signal of 30 Hz produced from a movie film of 24 Hz, and said duplicate field determining means further comprises:

a memory for storing said cumulative values;

a means for determining that said current field is potentially a duplicate field by detecting that the cumulative value of said current field is smaller than said first threshold value for detecting a duplicate field; and

a means for detecting that said potentially duplicate field is a duplicate field by detecting that four consecutive cumulative values are greater than said second threshold value for detecting a non-duplicate field, wherein said four consecutive cumulative values are for fields adjacent to said potentially duplicate field.

38. The image signal processor according to claim 29, wherein said duplicate field detecting means detects duplicate fields based on said image signal relating to partial data of a first field.

39. The image signal processor according to claim 29, said duplicate field detecting means further comprising:

a field memory storing two fields of said image signal and outputting said image signal to said subtracting means;

an absolutizing means for obtaining a plurality of absolute values by absolutizing said field differential values obtained by said subtracting means;

a one-field cumulative adder means for obtaining a plurality of cumulative values by accumulating absolute values, wherein each of said cumulative values relates to one of said first fields and said second fields;

a cumulative value memory for storing said cumulative values;

a threshold value memory storing said threshold value for detecting a duplicate field; and

a threshold value determining means for determining said threshold value for detecting a non-duplicate field based on one of said cumulative values, wherein

said duplicate field determining means is operatively connected to said one-field cumulative adder means, said cumulative value memory, said threshold value memory, and said threshold value determining means, and determines said duplicate field by checking said pattern of appearance of duplicate and non-duplicate fields based on said first threshold value for detecting a duplicate field, said second threshold value for detecting a non-duplicate field, and said plurality of field differential values.

40. The image signal processor according to claim 29, wherein said duplicate field removing means removes one of said plurality of first fields which temporally antecedes and corresponds to a duplicate field detected by said duplicate field detecting means when said detected duplicate field corresponds to said plurality of first fields, and removes said detected duplicate field when said detected duplicate field corresponds to said plurality of second fields.

28. An image signal processor, comprising:

a duplicate field detector detecting a duplicate field of an image signal based on a first threshold value for detecting a duplicate field and data of a current field, said duplicate field detector determining whether said current field is a non-duplicate field by comparing said cumulative value for said current field of said image signal with said first threshold value and detecting said current field as a non-duplicate field when the cumulative value for said current field is greater than said first threshold value and by detecting, with a second threshold when said cumulative value for said current field is less than said first threshold value, a plurality of adjacent fields of said image with little motion, said adjacent fields being adjacent to said current field; and

a duplicate field removing means for removing said duplicate field detected by said duplicate detector.