DIGITAL VIDEO COMPRESSION ACCELERATION BASED ON MOTION VECTORS PRODUCED BY CAMERAS

• US 20090290641A1
• Filed: 05/22/2008
• Published: 11/26/2009
• Est. Priority Date: 05/22/2008
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Crinon, Regis J., Ali, Walid
• Granted Patent: US 8,571,106 B2
• Time in Patent Office: Days
• US Class Current: 375/240.16
• CPC Class Codes: H04N 19/46 Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take precedence
• CPC Class Codes: H04N 19/521 for estimating the reliability of the determined motion vectors or motion vector field, e.g. for smoothing the motion vector field or for correcting motion vectors
• CPC Class Codes: H04N 19/523 with sub-pixel accuracy
• CPC Class Codes: H04N 19/56 Motion estimation with initialisation of the vector search, e.g. estimating a good candidate to initiate a search
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

Architecture for accelerating video compression by using the motion vectors produced locally by a camera. Video frames are captured by the camera (e.g., a webcam) which also computes a motion vector for the frame. Metadata can also be generated that represent an index of motion quality associated with the motion vector. The motion vector is passed to a video compression engine which selectively uses the motion vector directly or alternatively as a seed for a compression and encoding algorithm. This algorithm produces a compressed video frame representing a motion estimate having a selected motion quality index value. In this way, complexity is reduced in the video compression engine, resulting in faster and more efficient video compression. Alternatively, the webcam sends a compressed video bitstream to reduce throughput on the connection and the receiving computing system processes residual information to derive an estimate of the quality index for each macroblock/kernel.

Claims

1. A computer-implemented system for processing digital data, comprising:

an analysis component of a camera for computing a motion vector of a frame in a video stream; and

a communications component for communicating the motion vector to a compression engine for estimating motion in the video stream.

2. The system of claim 1, wherein the analysis component computes metadata for the motion vector, and the communications component communicates both the motion vector and the associated metadata to the compression engine.

3. The system of claim 2, wherein the metadata comprises a motion quality index associated with the motion vector, the motion quality index defines a ranked set of ranges of average distortion per pixels in the frame.

4. The system of claim 1, wherein the compression engine further comprises a motion estimation component for modifying the motion vector in response to a predetermined motion quality index value.

5. A computer-implemented system for processing digital data, comprising:

a video capture component for generating a frame of a video stream;

an analysis component for computing motion vectors for corresponding blocks in the frame and metadata representing a motion quality index associated with each motion vector; and

a compression engine for receiving the motion vectors, the metadata, and the frame of the video stream, and producing a compressed video frame representing a motion estimate having a predetermined motion quality index value.

6. The system of claim 5, wherein the compression engine further comprises a motion estimation component for modifying the motion vectors according to the metadata to produce respective modified motion vectors.

7. The system of claim 6, further comprising a rate controller for selectively controlling whether the motion vectors are sent directly to the compression engine or first modified by the motion estimation component based on the motion quality index value.

8. The system of claim 5, wherein the motion quality index value defines a ranked set of ranges of average distortion per pixel in the frame.

9. The system of claim 5, wherein the video capture component is a webcam for sending the frame via a data pipeline to a computing component comprising at least the compression engine.

10. The system of claim 5, further comprising a shared memory component for storing the motion vectors, the metadata, and the motion quality index value for selective retrieval and re-use by the compression engine for realtime communications between the video capture component and a communications application.

11. The system of claim 5, wherein the metadata further comprises global metadata transmitted at call setup, the global metadata includes at least one of pixel depth, a quality metrics table associating the quality index with ranges of average pixel distortion corresponding to pixel depth, a motion estimation algorithm identifier, a sub-pixel interpolation identifier, mode identifier, or frame size identifier.

12. The system of claim 5, wherein the metadata further comprises frame metadata transmitted at a beginning of the frame, the frame metadata includes a frame timestamp associated with the frame.

13. The system of claim 5, wherein the metadata further comprises motion vector metadata of a block associated with each motion vector and transmitted during a call, the motion vector metadata includes at least one of a shape and size specification of the block, a position value of the block, a chrominance/luminance value of the block, a frame reference identifier, the quality index, or a sub-pixel motion estimate.

14. A computer-implemented method of processing digital data, comprising:

computing a motion vector of a frame in a video stream in a camera; and

compressing the frame in accordance with the motion vector to compensate for estimated motion in the video stream.

15. The method of claim 14, further comprising computing metadata for the motion vector, the frame is compressed in accordance with both the motion vector and the metadata to compensate for estimated motion in the video stream.

16. The method of claim 15, wherein computing the metadata comprises deriving a motion quality index associated with the motion vector, the motion quality index defines a ranked set of ranges of average distortion per pixels in the frame.

17. The method of claim 16, further comprising selectively modifying the motion vector based on the motion quality index.

18. The method of claim 16, wherein the motion quality index defines a ranked set of ranges of average distortion per pixel in the frame.

19. The method of claim 14, further comprising multiplexing the frame with the motion vector.

20. The method of claim 14, further comprising separately sending the frame and the motion vector.