Video Object Tracking and Replacement for Post TV Production LYU0303 Final Year Project Spring 2004

Outline Brief project overview and targets achieved New components added to the proposed system Working principles of individual parts Future work Q & A

Overview Post-TV production processes and changes the content of a video clip Difficult for computers to process video in a global view Step-by-step programming enables the computer to think more thoroughly

Overview We have introduced the following parts in the last semester: Bitmap I/O RGB HSV converter Edge detector Edge equation finder Translation detector Texture mapper New parts have been added in order to increase the functionality of the system

Additional Basic Components The following parts have been added Graphical User Interface (GUI) Corner point finder Video file reader and writer Video player processor (frame-based) Improved texture mapper The following part has been modified Bitmap I/O Edge finder Texture mapper Removed Equation processor

Graphical User Interface Although UI is not a main project part, a good GUI can significantly decrease the time needed for processing and program maintenance Since C++ language is being used, the Microsoft Foundation Classes are adopted to develop the user interface Provide most of the basic functions needed for information input and output

Graphical User Interface

Corner Point Finder As we know that processing dots are much faster than processing lines, we may wish to try to find the corner points directly before finding the edge equations Stick some brightly coloured labels at the corners of the rectangular surface Can apply on cylindrical objects as well to indicated the curve control points A simple K-Means method is used to group the points together.

Corner Point Finder In order to know the orientation of the mapped texture, we need to know which is the first point For simplicity we just make the first point larger so that it contains more corner points than the others First point

Corner Point Finder We repeat the process until all the corner points has been processed Points which are too far away from the main groups are discarded Find out the centroids of the groups and move them out to give an estimation of corner positions GroupNo. of Member

Corner Point Finder

Video File I/O As we are talking about video processing, it is inevitable to handle video reading and writing DirectShow interfaces are being used in the project Able to process any type of AVI video as long as the Window Media Player can play them

Video Player We need to choose a video renderer that is suitable for our application To reserve the function of real-time processing and video texture in the future, the Video Mixing Renderer 9 (VMR9) is used Allows the rendering of more than one video or bitmap on the screen at the same time

Video Processor Video are sequence of bitmap frames We capture each video frame and process them in the same way as processing the bitmaps After a video frame is being processed, we add them to an AVI file Default video compressor is DivX Mpeg4 encoder (FourCC code divx)

Video Renderer Video System Structure

Texture Mapper A graphics design technique used to wrap a surface of a 3-D object with a texture map The 3-D object acquires a surface texture similar to the texture map. Colors, brightness values or altitudes

Texture Mapper Mapping function (u,v) (r,c) Texture coordinates Image coordinates

line by line process each pixel on every line last semester, we mapped cubes. How about this semester? Scan-line conversion Scanline y k Scanline y k+1 scanning order for every line

Cylindrical mapping How to map this cylinder with different textures?

Cylindrical mapping Mapping cylinders 3 parts: Surface detection Line scanning Texture lookup + Orientation determination

Surface detection 1. Hough algorithm to detect the two straight edges four points are detected

Surface detection 2. Scanning from top to bottom the scanning slope is orthogonal yellow points are detected by color transition

Surface detection 3. Model the curved edges by ellipses x 2 / a 2 + y 2 / b 2 = 1 2 ellipses are needed rotational factor x y z

Scan-line mapping 4. Scan-line from left to right Problem: How to determine the corresponding texture for each pixel, say p=(x,y) ? x y z (x,y)

Texture lookup 5. Rotate the cylinder to the upright position along z-axis 6. Translate the cylinder to (0,0) and determine the z coordinate p=(x,y,z) 7. Rotate the along x- axis upright from viewpoint x y z (0,0) h

Texture lookup 8. Detect the marker which indicates where the texture starts 9. Look up the texture coordinate (u,v) by (y+h/2)/h = v tan -1 (x/z) / 2 = u x y z (u,v)

Cylindrical mapping After mapping the top we have : TEXTURES MAPPING MAPPED CYLINDER

Spherical mapping How to map this sphere with different textures?

Spherical mapping Mapping spheres Also 3 parts: Surface detection Line scanning Texture lookup + Orientation determination

Surface detection 1. Scan from 4 directions and get the boundary points 2. Determine center

Line scanning 3. Scan from left to right. 4. For each pixel p=(x,y), look up the texture by transforming it to the upright position x y z (0,0) Upright

Texture lookup 4. Translate to origin 5. Look up z- coordinate 6. Rotate the ball along z-axis 7. Rotate the ball along x-axis (x,y,z) x y z (0,0) (5) (6)

Texture lookup 8. Lookup the texture by v = cos -1 (y/R) / u = (cos -1 (x/(R sin(v ))) ) / (2 )

Spherical mapping After mapping: Mapped Sphere Texture

Shadow mapping Mapping of surface brightness Method: Covert the image from RGB HSV Modify the V (intensity) value 5 types of shadow mapping

Shadow mapping 1. Mapping with texture brightness often unrealistic 2. Mapping with image brightness

Shadow mapping 3. Mapping with average brightness of the image more realistic 4. Mapping with other shadow maps (e.g. wood)

Shadow mapping 5. Transparency mapping (background information has to be obtained)

Problem with sphere mapping The texture is squeezed at the pole

Solution Modify the texture to this: Mapped sphere becomes: No distortion at pole

Q & A