Method and apparatus for identifying video fields produced by film sources

A method of film mode detection of an interlaced video signal, comprising:

• concurrently providing selected pixels comprising a first pixel from a given field and second and third vertically aligned pixels of the same horizontal position from a temporally adjacent field;
• comparing values of said selected pixels to produce for each first pixel, a pixel difference signal having a value of zero if the value of said first pixel is intermediate the values of said second and third pixels, said pixel difference signal otherwise having a value equal to an absolute value of a pixel difference between the value of said first pixel and the value of one of said second and third pixels having a value closest to the value of said first pixel;
• accumulating non-zero values of said pixel difference signals over a predetermined portion of one field period of said interlaced video signal to provide a field difference signal;
• analyzing said accumulated field difference signals for a pattern indicative of a film source of said video signal;
• and wherein generation of said pixel difference signal in said comparing step includes:
• median filtering said first, second and third pixels to form a median filtered signal;
• subtractively combining said median filtered signal and said first pixel to form a combined signal;
• and
• forming an absolute value of said combined signal to produce said pixel difference signal.

Apparatus for providing film mode detection of an interlaced video signal, comprising:

• a pixel selection circuit responsive to said video signal for concurrently providing a first pixel from a given field and second and third vertically aligned pixels of the same horizontal position from a temporally adjacent field;
• a pixel comparison circuit for comparing values of said selected pixels to produce for each first pixel, a pixel difference signal having a value of zero if the value of said first pixel is intermediate the values of said second and third pixels, said pixel difference signal otherwise having a value equal to an absolute value of a pixel difference between the value of said first pixel and the value of one of said second and third pixels having a value closest to the value of said first pixel;
• an accumulation circuit for accumulating non-zero values of said pixel difference signals over a predetermined portion of one field period of said interlaced video signal to provide a field difference signal;
• and
• an analyzer circuit for analyzing said accumulated field difference signals for a pattern indicative of a film source of said video signal;
• and
• wherein said pattern comprises two selectable patterns including a 2-2 pull down pattern and a 3-2 pull down pattern.

Apparatus for providing film mode detection of an interlaced video signal, comprising:

• a pixel selection circuit responsive to said video signal for concurrently providing a first pixel from a given field and second and third vertically aligned pixels of the same horizontal position from a temporally adjacent field;
• a pixel comparison circuit for comparing values of said selected pixels to produce for each first pixel, a pixel difference signal having a value of zero if the value of said first pixel is intermediate the values of said second and third pixels, said pixel difference signal otherwise having a value equal to an absolute value of a pixel difference between the value of said first pixel and the value of one of said second and third pixels having a value closest to the value of said first pixel;
• an accumulation circuit for accumulating non-zero values of said pixel difference signals over a predetermined portion of one field period of said interlaced video signal to provide a field difference signal;
• and
• an analyzer circuit for analyzing said accumulated field difference signals for a pattern indicative of a film source of said video signal;
• and wherein
• said pixel comparison circuit comprises;
• means for median filtering said first, second and third pixels to form a median filtered signal;
• means for subtractively combining said median filtered signal and said first pixel to form a combined signal and
• means for forming an absolute value of said combined signal to produce said pixel difference signal.