Difference between revisions of "BEAR4 compression"
From ScienceZero
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WORK IN PROGRESS... | WORK IN PROGRESS... | ||
| − | BEAR4 is designed for microcontrollers that have little RAM. It uses the data decompressed so far as the dictionary, compared to typical LZ compression this decreases efficiency since the index range must be larger and the need for storing the count. Most of the loss is recovered by only reading the number of bits required for the current range. | + | BEAR4 is designed for microcontrollers that have little RAM. It uses the data decompressed so far as the dictionary, compared to typical LZ compression this decreases efficiency since the index range must be larger and the need for storing the count. Most of the loss is recovered by only reading the number of bits required for the current index/count range. |
Header | Header | ||
| Line 10: | Line 10: | ||
c - maximum count size (1-16) | c - maximum count size (1-16) | ||
| + | Data | ||
0 <symbol> | 0 <symbol> | ||
1 <index> <count> | 1 <index> <count> | ||
| + | Pseudocode | ||
do | do | ||
indexSize = min(log2(decompressedSize), maximumIndexSize) | indexSize = min(log2(decompressedSize), maximumIndexSize) | ||
Revision as of 11:14, 31 August 2014
WORK IN PROGRESS...
BEAR4 is designed for microcontrollers that have little RAM. It uses the data decompressed so far as the dictionary, compared to typical LZ compression this decreases efficiency since the index range must be larger and the need for storing the count. Most of the loss is recovered by only reading the number of bits required for the current index/count range.
Header
BE4R - file ID
s - symbol size (1-64)
h - symbol shift (0-63)
i - maximum index size (1-32)
c - maximum count size (1-16)
Data
0 <symbol> 1 <index> <count>
Pseudocode
do
indexSize = min(log2(decompressedSize), maximumIndexSize)
countSize = min(indexSize, maximumCountSize)
read classBit
if classBit = 0 then
read symbol
output symbol
else
read index, count
for each count
read symbolFromDecompressed
output symbol
next
endif
loop
