Fast video encoder using adaptive hierarchical video processing in a down-sampled domain

• US 20020196854A1
• Filed: 06/15/2001
• Published: 12/26/2002
• Est. Priority Date: 06/15/2001
• Status: Abandoned Application

• Current Assignee: Media Excel, Inc.
• Original Assignee: Media Excel, Inc.
• Inventors: Kim, Jongil
• Application Number:
  US09/882,008
• Publication Number:
  US 20020196854A1
• Time in Patent Office: Days
• US Class Current: 375/240.17
• CPC Class Codes: H04N 19/523 with sub-pixel accuracy
• CPC Class Codes: H04N 19/53 Multi-resolution motion estimation; Hierarchical motion estimation
• CPC Class Codes: H04N 19/59 involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
• CPC Class Codes: H04N 5/145 Movement estimation for video coding H04N19/51

Abstract

A video encoding method and apparatus is presented that substantially reduces the computational requirements for motion processing by analyzing macro-blocks of down-sampled video frames to determine down-sample motion vectors from which motion vectors for the macro-blocks of the video frames are derived.

Claims

1. A video encoder, comprising:

a down sampler for transforming each of a succession of video frames to a corresponding down-sample frame containing fewer pixels than the corresponding video frame from which it is derived;

a scene analyzer for analyzing one or more macro-blocks of pixels of a down-sample frame to determine for each of the one or more macro-blocks an adaptive search range;

a high-level motion estimator for determining for each analyzed macro-block a down-sample motion vector within the adaptive search range derived from analysis of the macro-block performed by the scene analyzer;

a low-level motion estimator for deriving for each down-sample motion vector a full-sample motion vector within a search range derived from the down-sample motion vector.

2. The video encoder of claim 1, wherein the scene analyzer further comprises:

classification of each analyzed macro-block;

wherein the classification determines whether the down-sample vector for the macro-block is deemed to be zero or is a vector that provides a lowest value of an error function among a set of vectors within the adaptive search range.

3. The video encoder of claim 2, wherein the classification of the macro-block further determines the resolution of search for the full-sample motion vector.

4. The video encoder of claim 1, wherein the scene analyzer further comprises:

classification of each analyzed macro-block;

wherein the classification of the macro-block determines the resolution of search for the full-sample motion vector.

5. The video encoder of claim 4, wherein classification of the macro-block determines whether the low-level motion estimator is:

bypassed;

or

operates in an integer-pixel resolution mode, followed by a half-pixel resolution mode;

or operates in a half-pixel resolution mode only.

6. The video encoder of claim 1, wherein low-level motion estimation further comprises determining according to a distribution of error function values computed by the high-level motion estimator a set of candidate search vectors from which the full-sample motion vector may be determined within the search range derived from the down-sample motion vector.

7. The video encoder of claim 6, wherein the low level motion estimator:

is operable in an integer-pixel resolution mode wherein a set of search positions for determining an integer-pixel resolution motion vector within the search range derived from the down-sample motion vector is selected according to a distribution of error function values computed by the high-level motion estimator; and

is operable in a half-pixel resolution mode wherein a set of search positions for determining a half-pixel resolution motion vector is selected according to a distribution of error function values computed in the integer-pixel resolution mode.

8. The video encoder of claim 1, wherein the down sampler down-samples a video frame in each dimension of the frame by equal scale factors.

9. The video encoder of claim 1, wherein the scene analyzer further determines whether the encoder operates in an inter-frame mode or an intra-frame mode.

10. A video encoding method, comprising the steps of:

down-sampling each of a succession of video frames to produce a corresponding down-sample frame containing fewer pixels than the corresponding video frame from which it is derived;

analyzing one or more macro-blocks of pixels of a down-sample frame to determine an adaptive search range for each of the one or more macro-blocks;

determining a down-sample motion vector for each macro-block within the adaptive search range derived from analysis of the each macro-block of the down-sample frame; and

deriving for each down-sample motion vector a full-sample motion vector that provides a lowest value of an error function among a set of one or more candidate vectors within a search range derived from the down-sample motion vector.

11. The video encoding method of claim 10, wherein analysis of a macro-block of a down-sample frame further comprises the steps of:

classification of each macro-block of a down-sample frame;

wherein a down-sample vector is deemed to be zero or is a vector that provides a lowest value of an error function among a set of vectors within the adaptive search range according to the classification of the macro-block.

12. The video encoding method of claim 10, wherein the resolution of the full-sample motion vector is determined according to a classification of the macro-block of the down-sample frame to which the full-sample motion vector corresponds.

13. The video encoding method of claim 12, wherein determination of a full-sample motion vector is performable in an integer-pixel resolution mode and a half-pixel resolution mode.

14. The video encoding method of claim 10, wherein a full-sample motion vector is determined from a set of candidate search positions derived from analysis of a distribution of error function values computed within the adaptive search range derived from analysis of the macro-block.

15. The video encoding method of claim 10, wherein determination of a full-sample motion vector is performable in an integer-pixel resolution mode and a half-pixel resolution mode and:

in the integer-pixel resolution mode, an integer-pixel resolution motion vector is determined from a set of candidate search positions derived from analysis of a distribution of error function values computed within the adaptive search range derived from analysis of the macro-block; and

in the half-pixel resolution mode, a half-pixel resolution motion vector is determined from a set of candidate search positions derived from analysis of a distribution of error function values computed from the set of candidate search positions determined in the integer-pixel resolution mode.

16. The video encoder of claim 10, wherein a frame is down-sampled in each dimension of the frame by equal scale factors.

17. The video encoder of claim 10, wherein analysis of a macro-block further determines whether the encoder operates in an inter-frame mode or an intra-frame mode for transmission of video data corresponding to the macro-block.

19. The motion processing method of claim 18, wherein analysis of each down-sample macro-block further comprises the step of:

determining the down-sample motion vector that provides the lowest value of an error function within an adaptive search range determined by one or more measures of the extent to which the down-sample macro-block data deviates from the data of the identically positioned down-sample macro-block within a previously analyzed down-sample frame.

20. The video encoding method of claim 18, wherein determination of the full sample motion vector further comprises the step of:

conducting a search for the full sample motion vector that minimizes an error function within a search range conducted in the vicinity of a reference vector derived from the down-sample motion vector.

18. A method for motion processing in a digital video encoder, comprising the steps of:

deriving from each video frame of a succession of video frames of a moving picture a down-sample frame containing a reduced set of pixels representative of information in the video frame from which the down-sample frame is derived;

the down-sample frame comprising one or more down-sample macro-blocks of pixels, each down-sample macro-block corresponding to a full sample macro-block of pixels in the video frame;

analyzing the one or more down-sample macro-blocks in each down-sample frame to determine for each analyzed down-sample macro-block a down-sample motion vector representative of motion of the down-sample macro-block between adjacent down-sample frames;

determining for each down-sample motion vector a full-sample motion vector representative of the motion of the corresponding full-sample macro-block between adjacent video frames.