Digital Signal Processing Reference
In-Depth Information
clearly what this objective test method for assessing the picture quality
amounts to:
16
16
AD(i=0)
AD(i=1)
AD(i=2)
AD(i=3)
AD(i=4)
AD(i=5)
AD(i=6)
AD(i=7)
AD(i=8)
AD(i=9)
AD(i=10)
AD(i=11)
AD(i=12)
AD(i=13)
AD(i=14)
AD(i=15)
AD(i=0)
AD(i=1)
AD(i=2)
AD(i=3)
AD(i=4)
AD(i=5)
AD(i=6)
AD(i=7)
AD(i=8)
AD(i=9)
AD(i=10)
AD(i=11)
AD(i=12)
AD(i=13)
AD(i=14)
AD(i=15)
14
14
12
12
10
10
8
8
6
6
4
4
2
2
0
0
0
0
2
2
4
4
6
6
8
8
10
10
12
12
14
14
16
16
18
18
20
20
22
22
24
24
26
26
Frame number
Frame number
16
16
AD(i=0)
AD(i=1)
AD(i=2)
AD(i=3)
AD(i=4)
AD(i=5)
AD(i=6)
AD(i=7)
AD(i=8)
AD(i=9)
AD(i=10)
AD(i=11)
AD(i=12)
AD(i=13)
AD(i=14)
AD(i=15)
AD(i=0)
AD(i=1)
AD(i=2)
AD(i=3)
AD(i=4)
AD(i=5)
AD(i=6)
AD(i=7)
AD(i=8)
AD(i=9)
AD(i=10)
AD(i=11)
AD(i=12)
AD(i=13)
AD(i=14)
AD(i=15)
14
14
12
12
10
10
8
8
6
6
4
4
2
2
0
0
0 2 4 6 8 0 2 4 6 8 0 2 4 6
0 2 4 6 8 0 2 4 6 8 0 2 4 6
Frame number
Frame number
Fig. 12.5.
Averaged macroblock pixel differences in a video sequence with good
picture quality (top, flower garden/original, 6 Mbit/s) and with poorer picture
quality (bottom, flower garden/MPEG-2, 2 Mbit/s)
Fig. 12.5. shows clearly that the pixel amplitude differences in the
“good” video sequence are very close to each other for all 16 pixel differ-
ences within the macroblocks. In the present example, they are all at about
10 ... 12.
In a video sequence with “poor” quality (bottom display) with blocking,
it can be seen that the macroblock borders exhibit greater jumps, i.e the
pixel differences are greater there.
It can be seen clearly that pixel differences No. 0 and No. 8, in the bot-
tom display, are obviously greater than the remaining difference values.
Search WWH ::
Custom Search