1. Memory Management for Multimedia Signal Processing
Elec4622, Week 2, Term 2
A/Prof. David Taubman

2. Dynamic Arrays In 1-D In 2-D int *C = new int[4];
C[0]=3; C[1]=4; C[2]=1; C[3]=0;
In 2-D
int **C = new int *[4];
for (int r=0; r < 4; r++)
C[r] = new int[5];
(C[1])[3] = 45; … C 3 4 1 C 45

3. Single Block of Memory Keep image contiguous in memory Advantages
int rows=4, cols=5;
int *C = new int[rows*cols];
int r=1, c=3;
C[cols*r+c] = 45;
Advantages
usually faster access (better cache utilization)
only one memory de-reference operation
a pixel’s neighbours have fixed memory offsets relative to the address of the pixel. C 45

4. Making Algorithms Look Natural
Visit pixels 1 by 1 and do local processing:
for (r=0; r < rows; r++)
for (c=0; c < cols; c++) {
int *ipel = input + r*cols + c;
int *opel = output + r*cols + c;
int avg = ipel[0] / 2
+ (ipel[-1] + ipel[1]
ipel[-cols] + ipel[cols])/8;
*opel = avg; }
Can you see any problems?

5. Adding Extra Space Allocate more memory Notice that:
int rows=4, cols=5, stride=cols+2;
int *H = new int[(rows+2)*stride];
int *C = handle + stride+1;
int r=1, c=3;
C[stride*r+c] = 45;
…..
delete[] H;
Notice that:
C points to first real pixel
Row and column addresses can be –ve when applied to C H C 45

6. Considerations for Video
Cannot store whole video
Keep a moving window, using lists
Recycle frames which drop off the window H H C H C
frame_idx C
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