Pulldown correction for progressive display of audiovisual recordings
AssigneeApple Inc.
InventorCecile M. Foret
Life of this patent
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Abstract
Embodiments of the present invention relate to methods and systems that may detect cadences and duplicate fields in a video sequence, and correct the sequence to retrieve the original progressive content. Methods according to the present invention may compare consecutive fields of the same parity for similarity, and consecutive fields of the opposite parity for field and frame activity. By analyzing patterns in the similarity and activity of the fields, the cadence may be determined. The invention also provides methods that may be used to adjust for changes in the cadence, such as can result from scene changes in the video stream.
Claims30
A cadence detection method for a sequence of video data received at a video coder, the video data populated by fields of video content, comprising, for a plurality of candidate fields from the sequence:
- generating, with the coder, a similarity measure from a comparison of image content of the candidate field to corresponding content of a same-parity field immediately prior to the candidate field in display order,
- determining, with the coder, a level of activity in the candidate field,
- determining, with the coder, a level of activity of an opposite-parity field immediately prior to the candidate field in display order,
- determining, with the coder, a level of activity of a frame formed from the candidate field and the opposite-parity field,
- comparing, with the coder, the activity of the frame to an aggregate of the activity of the candidate field and the activity of the opposite-parity field, and
- assigning, with the coder, a cadence to the video sequence based on the similarity measures and the activity comparisons among the plurality of fields;
- wherein assigning a cadence to the video sequence includes identifying a pattern in fields with a low activity comparison;
- wherein a field has a low activity comparison if the activity comparison is below a predetermined percentage of the activity comparison of a second field.
A method for determining the type of an original video stream received at a video coder, the original video stream represented by a sequence of fields of video content, comprising, for a plurality of candidate fields from the sequence:
- generating, with the coder, a similarity measure from a comparison of image content of the candidate field to corresponding content of a same-parity field immediately prior to the candidate field in display order,
- determining, with the coder, a level of activity in the candidate field,
- determining, with the coder, a level of activity of an opposite-parity field immediately prior to the candidate field in display order,
- determining, with the coder, a level of activity of a frame formed from the candidate field and the opposite-parity field,
- comparing, with the coder, the activity of the frame to an aggregate of the activity of the candidate field and the activity of the opposite-parity field, and
- assigning, with the coder, a cadence to the video sequence based on a pattern of the similarity measures and the activity comparisons among the plurality of fields;
- wherein the pattern of similarity measures is identified in fields with a low activity comparison;
- wherein a field has a low activity comparison if the activity comparison is below a predetermined percentage of the activity comparison of a second field.
A system for detecting the cadence of a video stream, comprising:
- a buffer to receive sequential fields of the video stream;
- and
- a video coder to:
- generate a similarity measure from a comparison of image content of a candidate field to corresponding content of a same parity field immediately prior to the candidate field,
- determine a level of activity in the candidate field;
- determine a level of activity of an opposite-parity field immediately prior to the candidate field in display order,
- determine a level of activity of a frame formed from the candidate field and the opposite-parity field,
- generate an activity comparison for the activity of the frame to an aggregate of the activity of the candidate field and the activity of the opposite-parity field, and identify repeat fields in the video stream and generate a cadence to the video stream based on a pattern in the similarity measures and the activity comparisons among the plurality of fields;
- wherein the pattern is identified for fields with a low activity comparison;
- wherein a field has a low activity comparison if the activity comparison is below a predetermined percentage of the activity comparison of a second field.
A system for detecting the type of a video stream, comprising:
- a buffer to receive sequential fields of the video stream;
- and
- a video coder to:
- generate a similarity measure from a comparison of image content of a candidate field to corresponding content of a same-parity field immediately prior to the candidate field,
- determine a level of activity in the candidate field;
- determine a level of activity of an opposite-parity field immediately prior to the candidate field in display order,
- determine a level of activity of a frame formed from the candidate field and the opposite-parity field,
- generate an activity comparison of the activity of the frame to an aggregate of the activity of the candidate field and the activity of the opposite-parity field, and
- identify repeat fields in the video stream and determine the format of the original video stream based on a pattern of repeat fields;
- wherein repeat fields are identified by identifying a pattern in fields with a low activity comparison;
- wherein a field has a low activity comparison if the activity comparison is below a predetermined percentage of the activity comparison of a second field.
Dependencies are inferred from the claim text.