METHOD AND APPARATUS FOR MODIFYING A VIDEO STREAM TO ENCODE METADATA

• US 20140161304A1
• Filed: 12/11/2013
• Published: 06/12/2014
• Est. Priority Date: 12/12/2012
• Status: Active Grant

• Current Assignee: Grass Valley USA Incorporated
• Original Assignee: Snell Limited (Belden Inc.)
• Inventors: Diggins, Jonathan
• Granted Patent: US 9,330,428 B2
• Time in Patent Office: Days
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0061 Embedding of the watermark in each block of the image, e.g. segmented watermarking
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection

Abstract

A watermark encoder receives a current video image together with current metadata associated with the current image. A metadata delay also makes available to the watermark decoder delayed metadata associated respectively with four or more of the preceding. Then the watermark encoder modifies pixel values of the current image not only to encode the current metadata but also the delayed metadata. At a decoder, if metadata for the current image is corrupted or missing, it can be recovered from one of the succeeding images.

Claims

1. A method of modifying video data to encode metadata, comprising:

receiving in a video processor a sequence of video images, each image having metadata associated with it, the metadata associated with each of the video images differing from the metadata associated with at least one other of the video images, each video image comprising pixel data defining pixel values of that image;

for an image, collecting in the video processor the metadata associated with that image and the metadata associated respectively with N of the images preceding that image in the sequence of images, where N is equal to or greater than four; and

modifying in the video processor the pixel data of an image to encode the metadata associated with that image and to encode the metadata associated respectively with N of the images preceding that image in the sequence of images.

2. A method according to claim 1 in which every image is modified to encode metadata associated with itself and at least four immediately preceding images.

3. A method according to claim 1 in which pixel activity is measured within a region surrounding each pixel and pixel values are only modified when activity measured within a region surrounding the pixel to be modified exceeds a threshold.

4. A method according to claim 1 in which identical modifications are applied to the low-significance bits defining the values of all the pixels of a contiguous set of pixels comprising a spatial region within a field or frame so as to encode one or more bits of metadata within that spatial region of that field or frame.

5. A method according to claim 4 in which the two least-significant bits of a ten-bit value are modified.

6. A method according to claim 4 in which low-significance bits defining the values of a contiguous set of pixels in a spatial region within a field or frame are modified so as to encode a fixed data value within that region that aids the recognition of that fixed data value when encoded in a different spatial region within the said field or frame.

7. A method according to claim 4 in which identical data is encoded in a plurality of spatial regions within the same field or frame.

8. A method of processing a video data stream to decode metadata;

comprising

receiving in a video processor a sequence of video images, the pixel data of one video image having been modified to encode current metadata associated with that image and to encode other metadata for N other images respectively in the sequence of images, where N is equal to or greater than four;

testing for validity of the metadata encoded in an image;

if the metadata encoded in that image is valid, extracting in the video processor the metadata associated with that image and the other metadata for said N other images; and

associating said other metadata respectively with said N other images.

9. A method according to claim 8 comprising:

measuring the frequencies of occurrence of at least two combinations of values of low-significance pixel-value bits within a first spatial region within a field or frame;

measuring the frequencies of occurrence of at least two combinations of values of low-significance pixel-value bits within a second spatial region within the said field or frame; and

determining an encoded metadata parameter from a comparison of the frequencies of occurrence of combinations of low-significance pixel-value bits in the said first and second spatial regions of the said field or frame.

10. Apparatus for modifying video data to encode metadata, comprising:

a watermark encoder receiving a current video image in a sequence of video images together with current metadata associated with the current image;

a metadata delay for receiving metadata associated respectively with video images in the sequence of video images and for making available to the watermark decoder delayed metadata associated respectively with N of the images preceding a current image in a sequence of images, where N is equal to or greater than four;

wherein the watermark encoder is adapted to modify pixel data defining pixel values of the current image to encode said current metadata and said delayed metadata.

11. Apparatus according to claim 10 in which every image is modified to encode metadata associated with itself and at least four immediately preceding images.

12. Apparatus according to claim 10 in which pixel activity is measured and pixel values are only modified when activity measured within a region surrounding the pixel to be modified exceeds a threshold.

13. Apparatus according to claim 12 in which pixel activity is measured by a spatial filter.