Programmable system for motion vector generation

• US 20040190620A1
• Filed: 06/05/2003
• Published: 09/30/2004
• Est. Priority Date: 06/07/2002
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Alfonso, Daniele, Rovati, Fabrizio
• Granted Patent: US 7,272,184 B2
• Time in Patent Office: Days
• US Class Current: 375/240.16
• CPC Class Codes: H04N 19/43 Hardware specially adapted for motion estimation or compensation
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/56 Motion estimation with initialisation of the vector search, e.g. estimating a good candidate to initiate a search

Abstract

A system for generating motion vectors in a motion estimator is configured for co-operating with an engine for calculating estimation error for generating motion vectors, according to estimation errors and/or motion vectors previously generated. The system comprises a program memory that contains program data for a motion-estimation algorithm, and a motion-vector memory that contains data identifying said motion vectors previously calculated. The system further comprises an arithmetic and logic unit co-operating with the program memory and motion-vector memory to generate motion vectors in a programmable way to get them to correspond, for example, to predictors deriving from motion-estimation operations already performed on the macroblocks of the reference frame or on the previous macroblocks of the current frame, as updates calculated using the co-ordinates of the motion vectors already issued for the current macroblock, or as absolute motion vectors, generated as such, taking the components directly from the program code.

Claims

1. A system for generating motion vectors in the framework of a motion estimator, the system being configured for co-operating with an engine for calculating estimation error for generating motion vectors according to estimation errors and/or motion vectors previously generated, the system comprising:

a program memory that contains program data for a motion-estimation algorithm to be executed;

a motion-vector memory that contains data identifying said motion vectors previously generated; and

an arithmetic and logic unit co-operating with said program memory and said motion-vector memory, said arithmetic and logic unit being configured for performing at least one function comprised in the group consisting of;

arithmetical addition and subtraction of motion vectors in order to calculate new motion vectors using as reference said motion vectors previously generated;

definition of a current search window and logic comparisons on components of said motion vectors for verifying whether certain motion vectors exceed the limits of said search window;

logic comparisons on values of said estimation errors referred to different sets of motion vectors to be subjected to checking;

calculation of addresses of said memory of the motion vectors; and

addition of addresses of said program memory.

2. The system according to claim 1, further comprising loading means for loading into said motion-vector memory data identifying motion vectors previously generated following upon motion estimation performed:

on the macroblocks of one or more reference frames, the motion vectors thus generated being referred to as temporal predictors; and

on the previous macroblocks of the current frame, the corresponding motion vectors thus generated being referred to as spatial predictors.

3. The system according to claim 2, wherein said motion-vector memory comprises memory locations for storing, for each motion vector, a component for the horizontal direction and a component for the vertical direction, each component preferably being expressed in the form of sub-pixel co-ordinates.

4. The system according to claim 2 wherein said motion vector memory is organized in a plurality of independent areas, which can be separately accessed.

5. The system according to claim 4, wherein said motion-vector memory is at least partially located outside the system.

6. The system according to claim 1 wherein said arithmetic and logic unit is configured to carry out said calculation of the addresses of the motion-vector memory, fetching the correct temporal or spatial predictor, using as reference the co-ordinates of the current macroblock.

7. The system according to claim 1, further comprising a register-file module comprising at least one counter for following the number of the motion vectors so far generated for the current macroblock and the number of the partial results received from said engine for calculating estimation error.

8. The system according to claim 1, further comprising a register-file module with signals of data stored indicating at least one of the following values:

width of the current frame of the sequence;

height of the current frame of the sequence;

current dimension of the search window, defined as maximum and minimum values of each component of the motion vectors;

number of the current macroblock in the current frame;

co-ordinates of the current macroblock within the current frame;

motion vectors corresponding to the current optimal value of the estimation error calculated by said engine for calculating estimation error;

pointer indicating the motion vector considered to be optimal;

time distance between the current frame and the reference frame or frames; and

logic result of the comparisons made in said arithmetic and logic unit.

9. The system according to claim 1, further comprising an accumulator register, associated with said arithmetic and logic unit, for temporary storage of a motion vector that is to be processed in view of its being issued.

10. The system according to claim 1, further comprising a scaling module, between said motion-vector memory and said arithmetic and logic unit, for scaling the values of the motion vectors transferred form said memory to said arithmetic and logic unit.

11. The system according to claim 1, further comprising a state-control block for controlling operation of said engine for calculating estimation error by means of the generation of control-word signals identifying at least one of the following conditions:

type of current frame;

start of a new frame with the current motion vector;

start of a new macroblock with the current motion vector;

coarse or fine search for the motion vector;

type of current motion vector;

correspondence of the current motion vector with the zero vector;

character identifying the frame or the field of the current motion vector;

invalidity of the current motion vector;

need to take a final decision for the current macroblock;

possibility of getting round the decision on the current macroblock;

need to perform a simple transfer of the input data to the output; and

need to operate as motion compensator.

12. The system according to claim 11, wherein said control-word signals are generated by said state-control block in the form of flags.

13. The system according to claim 1 wherein said arithmetic and logic unit is selectively configurable in a plurality of operating conditions for generating motion vectors, said plurality of operating conditions corresponding to the following operating conditions:

generation of motion vectors as predictors deriving from a motion estimation already performed on the macroblocks of the reference frame or on the preceding macroblocks of the current frame;

generation of said motion vectors in the form of updates calculated using the co-ordinates of the motion vectors already generated for the current macroblock, with the addition thereto of a relative displacement; and

generation of said motion vectors as absolute motion vectors generated as such, by fetching the corresponding components from the program code.

14. A system for generating motion vectors, comprising:

an estimation error engine for calculating estimation error according to estimation errors and/or motion vectors previously generated; and

a motion estimation engine coupled to the estimation error engine and including;

a program memory that contains program data for a motion estimation algorithm to be executed;

a motion-vector memory that contains data identifying said motion vectors previously generated;

an arithmetic and logic unit co-operating with said program memory and said motion-vector memory, said arithmetic and logic unit being configured use the program data to calculate new motion vectors using as reference said motion vectors previously generated; and

a state controller coupled to the program memory and the error estimation engine and configured to control the error estimation by the error estimation engine based on the program data stored in the program memory.

15. The system according to claim 14, further comprising loading means for loading into said motion-vector memory data identifying motion vectors previously generated following upon motion estimation performed:

on the macroblocks of one or more reference frames, the motion vectors thus generated being referred to as temporal predictors; and

on the previous macroblocks of the current frame, the corresponding motion vectors thus generated being referred to as spatial predictors.

16. The system according to claim 15 wherein said arithmetic and logic unit is configured to carry out a calculation of addresses of the motion-vector memory, fetching a correct one of the temporal and spatial predictors, using co-ordinates of a current macroblock.

17. The system according to claim 14, further comprising a register-file module comprising a counter for following the number of the motion vectors so far generated for a current macroblock and the number of the partial results received from said estimation error engine.

18. The system according to claim 14 wherein the state controller is structured to generate of control-word signals identifying at least one of the following conditions:

type of current frame;

start of a new frame with the current motion vector;

start of a new macroblock with the current motion vector;

coarse or fine search for the motion vector;

type of current motion vector;

correspondence of the current motion vector with the zero vector;

character identifying the frame or the field of the current motion vector;

invalidity of the current motion vector;

need to take a final decision for the current macroblock;

possibility of getting round the decision on the current macroblock;

need to perform a simple transfer of the input data to the output; and

need to operate as motion compensator.

19. The system according to claim 14 wherein said arithmetic and logic unit is selectively configurable in a plurality of operating conditions for generating motion vectors, said plurality of operating conditions corresponding to the following operating conditions:

generation of motion vectors as predictors deriving from a motion estimation already performed on the macroblocks of the reference frame or on the preceding macroblocks of the current frame;

generation of said motion vectors in the form of updates calculated using the co-ordinates of the motion vectors already generated for the current macroblock, with the addition thereto of a relative displacement; and

generation of said motion vectors as absolute motion vectors generated as such, by fetching the corresponding components from the program code.

14-1. A method of generating motion vectors, comprising:

calculating estimation error according to estimation errors and/or motion vectors previously generated; and

storing in a program memory program data for a motion estimation algorithm to be executed;

storing in a motion-vector memory data identifying said motion vectors previously generated;

providing instructions from the program memory to an arithmetic and logic unit co-operating with said program memory to cause said arithmetic and logic unit to calculate new motion vectors using as reference said motion vectors previously generated; and

controlling the calculation of the error estimation by the error estimation engine based on the program data stored in the program memory.