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Image Processing
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Subband SAR Image Coding by using Quadtree Decomposition on Variable Block Truncation Code
IV. Subband And Variable Block Truncation Code (VBTC)
Image was reduced noise and pre-processed method will be divided into subband. In this case, we used the subband to 16 subbands as shown in Figure 3. for coding. Each subband is filtered and downsampled from filter bank stage and then is divided into small block by quadtree decomposition. The leave node of quadtree can be coded by setting the priority and coded by using VBTC [3,4] method. Subbands are defined as inter-subband and intra-subband [5] for arrangement the subband to coding. The Classification as inter-subband or intra-subband depends on whether they have the same parent source signal. In this case, subband HHLL and HHHH are the intra-subband because both of there are generated from the same parent source signal subband HH. Subband HHLL and LLLL are inter-subbands because their parent source signals are subband HH and LL, respectively
(a)
(b)
Figure 3. (a) 16 subbands structure, (b) Tree structure 16 subbands
V. Simulations and Results
In the experiment the original SAR images, with size 512 x 512 show in Fig. 4. (a),(c). It is divided by the QT method and differently encoded by VBTC for every leave node of the QT. The results are shown in Fig. 4. (b),(d). In Fig. 4 (b), SAR image are reconstructed and measured then evaluate mean square error and peak signal to noise ratio. This technique gives higher of peak signal to noise ratio than the BTC technique and can be reduced the processing time. Compression ratio depends on as a defined of the threshold in a quad tree technique. Table 1. illustrate a process time, mean square error (MSE) and peak signal to noise ratio (PSNR)of each image. The MSE and PSNR in the compression are expressed as
| image |
Bit Rate |
MSE(dB) |
PSNR |
Subband encoded with [1x1] , {2x2} |
Times (Sec.) |
| Tm4 |
1.2813 |
44.2823 |
31.6684 |
[ LLLL,LHLL,HLLL] |
353.94 |
| Tm4 |
0.4553 |
43.4394 |
31.6684 |
[ LLLL,LHLL,HLLL] |
321.1 |
| Sanfran |
2.875 |
17.7568 |
35.6371 |
[LLLL,LLHLLHLL,HLLL] |
1349 |
Sanfran |
0.8748 |
17.2611 |
35.6855 |
[LLLL,LLHLLHLL,HLLL] |
842.44 |
| Sar3 |
3.0625 |
40.0997 |
32.0033 |
[LLLL,LLHLLHLL,HLLL],{LLLH,LLHH} |
1430 |
| Sar3 |
0.9788 |
39.3096
| 32.1858 |
[LLLL,LLHLLHLL,HLLL],{LLLH,LLHH} |
850.03 |
Table 1. Simulations and results
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