H.264 Motion Vector Extractor - User Guide - Retrieving the motion information

H.264 Motion Vector Extractor
H.264 Motion Vector Extractor Basics
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Evaluating H.264 Motion Vector Extractor Getting the Code Building H.264 Motion Vector Extractor
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Preparing the buffer Retrieving the motion information Error codes
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This page provides a basic description of the output structures for the VectorExtractor class. From these structures the motion information can be retrieved for each frame in the stream.

Frame attributes

The Frame struct contains the following attributes to describe the result of extracting the motion vectors for a single frame.

Type

Name: type

Type: FrameType enum

This attribute describes the type of the frame held by the data buffer according to the H.264 types. The following types are supported:

• P_FRAME
• B_FRAME
• I_FRAME
• SP_FRAME
• SI_FRAME

However, only the P_FRAME type will contain extracted motion vectors.

Frame number

Name: frameNumber

Type: unsigned integer

This attribute specifies the sequential number of the frame according to the information parsed from the H.264 Slice headers.

Number of motion vectors

Name: numMotionVectors

Type: unsigned integer

This attribute specifies the total amount of extracted motion vectors from the current frame.

Motion vectors

Name: motionVectors

Type: shared pointer to an array of the MotionVector struct

This will contain all the extracted motion vectors inside an array of size numMotionVectors. The motion vectors will have the structure explained in the next section.

MotionVector attributes

The MotionVector struct contains the following attributes to describe the motion information for a macroblock or a partition of a macroblock (this can be determined with the mbWidth and mbHeight attributes).

Frame type

Name: frameType

Type: unsigned integer

This attribute contains the type of the current frame in the same format as extracted from the Slice header.

Source X

Name: srcX

Type: integer

This attribute specifies the X coordinate of the motion vector's source, meaning the macroblock's position in the previous frame.

Source Y

Name: srcY

Type: integer

This attribute specifies the Y coordinate of the motion vector's source, meaning the macroblock's position in the previous frame.

Destination X

Name: dstX

Type: integer

This attribute specifies the X coordinate of the motion vector's destination, meaning the macroblock's position in the current frame.

Destination Y

Name: dstY

Type: integer

This attribute specifies the Y coordinate of the motion vector's destination, meaning the macroblock's position in the current frame.

Macroblock width

Name: mbWidth

Type: integer

This is the width of the macroblock's partition for which the current motion vector applies. A width of 16 is as wide as the macroblock, 8 means simple macroblock partitioning while 4 indicates sub-macroblock partitioning.

Macroblock height

Name: mbHeight

Type: integer

This is the height of the macroblock's partition for which the current motion vector applies. A width of 16 is as tall as the macroblock, 8 means simple macroblock partitioning while 4 indicates sub-macroblock partitioning.