Detection of video feature based on variance metric
A metric representing the sum of variances for pixel blocks of a region of an image are used to identify the presence a video feature of the image, and a transcoding is performed responsive to identifying the presence of the video feature. The identified video feature can include, but is not limited to, a scene change, the presence of a black border region or a caption region, or the complexity of the image. The transcoding operation can include, but is not limited to, coding the image as an Intra-frame, omitting the content corresponding to the black border region or the caption region from the transcoded image or allocating a relatively lower bit budget for the black border region or a relatively higher bit budget to the caption region during transcoding of the image, or setting the bit budget for rate control during transcoding.
1. A system comprising:
a feature detection module to determine a first sum of variances metric representing a sum of variances of pixel blocks of a region of an image of a video signal, to determine a second sum of variances metric representing a sum of variances of pixel blocks of a corresponding region of at least the preceding image, and to determine the image represents a scene change based on a difference between the first sum of variances metric and an average sum of variances metric for a plurality of preceding images, the second sum of variances metric being represented in the average sum of variances metric; and
a transcoder to transcode the video signal to generate a transcoded video signal, the transcoder to perform at least one transcoding operation in response to the feature detection module determining the image represents a scene change.
2. The system of claim 1 , wherein the at least one transcoding operation comprises at least one of: generating a new group of pictures with a transcoded representation of the image as the first Intra-coded frame of the new group of pictures; and adjusting a rate control parameter for transcoding the image.
3. A method for transcoding a video signal, the method comprising:
determining, at a feature detection module of a transcoding system, a first sum of variances metric representing a sum of variances of pixel blocks of a region of an image of the video signal;
determining, at the feature detection module, a second sum of variances metric representing a sum of variances of pixel blocks of a corresponding region of at least the preceding image;
determining, at the feature detection module, the image represents a scene change based on a difference between the first sum of variances metric and an average sum of variances metric for a plurality of preceding images, the second sum of variances metric being represented in the average sum of variances metric; and
performing, at a transcoder of the transcoding system, at least one transcoding operation in response to determining the image represents a scene change to generate a transcoded video signal.
4. The method of claim 3 , wherein performing the at least one transcoding operation comprises at least one of: generating a new group of pictures with a transcoded representation of the image as the first Intra-coded frame of the new group of pictures; and adjusting a rate control parameter for transcoding the image.