Retinal Prosthesis Dissertation - Student Home Pages

the number of address bits will alter with image size. The number of address bits
required for various image sizes can be calculated from the following formula; where
the answer obtained is rounded up to the nearest whole number.
Log (pixel_count)/log2
side of square
address bits
log
image
10 pixel_count
required
Total bit length
2 0.60206 4 2 20
4 1.20412 16 4 22
8 1.80618 64 6 24
16 2.40824 256 8 26
32 3.0103 1024 10 28
1024 6.0206 1048576 20 38
Table 9 example correspondences
4.2.1 Alternative (discounted) sender AER format
An alternative robust AER format can be constructed whereby the bitstream consists
of ten bits of address (32 by 32 image) followed by a payload of 150 bits of which
the first 50 bits encode red plane information; the second 50 bits encode green plane
information and finally 50 bits of blue plane information. Such a format would be
more error tolerant in terms of loss of bits within the payload e.g. a two bit error
would be negligible but could only be achieved if a longer bit stream could be
tolerated. As this format will be integral to the receiver chip design it can justifiably
be used as part of the test setup to demonstrate that such a format can be output to a
monitor to display the picture expected to be formed. Programming components (or
extracts thereof) will be included in appendix B of this thesis.
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