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idea's on compression
6 answers - 563 bytes -
Hi all, just wondering if anybody has any idea's on compressing data
that is somewhat predictable or in a somewhat seq order
an example:
as you can see most of the numbers above seem incremental to a point.
33559 -3-5-9
0222244555568 -0-2-4-5-6-8
133 -1-3
1227778899 -1-2-7-8-9
0234579 -0-2-3-4-5-7-9
0 -just zero
so we have some kind of pattern that's somewhat predictable, what
advantage could I take
of this fact with compression?
any takers
Graham.
No.1 | | 573 bytes | |
houston wrote:
) Hi all, just wondering if anybody has any idea's on compressing data
) that is somewhat predictable or in a somewhat seq order
)
) an example:
)
)
)

<snip>

) advantage could I take
) of this fact with compression?

Delta encoding. Encode the difference from the previous number:
)

As you can see, lower numbers occur a lot more than higher numbers in this
series. You can take advantage of this by using some kind of entropy
encoder, such as Huffman or Arithcoding.

SaSW, Willem
No.2 | | 1687 bytes | |

"houston" <housty@hotmail.co.ukwrote in message
news:1157471474.606199.279630@
Hi all, just wondering if anybody has any idea's on compressing data
that is somewhat predictable or in a somewhat seq order

an example:
--

as you can see most of the numbers above seem incremental to a point.

33559 -3-5-9

0222244555568 -0-2-4-5-6-8

133 -1-3

1227778899 -1-2-7-8-9

0234579 -0-2-3-4-5-7-9

0 -just zero

so we have some kind of pattern that's somewhat predictable, what
advantage could I take
of this fact with compression?

for simple to implement answers:

different options are possible, depending on what you want. for example, if
your output is ascii-text (each byte representing a number) then many
options are possible (many of which could still produce valid ascii text).

eg, exploiting simple RLE compression:

0x000x1F, 0x20: as normal

0x210x2A: 09
0x2B0x33: 0099
0x340x3D: 000999
0x3E0x47: 00009999
0x480x51: 0000099999
0x520x5B: 000000999999
0x5C0x65: 00000009999999
0x660x6F: 0000000099999999
0x700x79: 000000000999999999

or (avoiding and non-alphanumeric chars):
0x300x39 ('0''9'): 09
0x410x4A ('A''J'): 0099
0x4B0x54 ('K''T'): 000999
0x610x6A ('a''j'): 00009999
0x6B0x74 ('k''t'): 0000099999

also possible (if ascii is not needed) is using a BCD like representation (4
bits/digit):
09: 09
AF: repeat last value 27 times

or such

any takers
Graham.
No.3 | | 710 bytes | |

Willem wrote:
houston wrote:
) Hi all, just wondering if anybody has any idea's on compressing data
) that is somewhat predictable or in a somewhat seq order
)
) an example:
)
)
)

<snip>

) advantage could I take
) of this fact with compression?

Delta encoding. Encode the difference from the previous number:
)

Hm Where is that kind of "encoding" useful? I guess it doesn't really
"compress" the given input ?

As you can see, lower numbers occur a lot more than higher numbers in this
series. You can take advantage of this by using some kind of entropy
encoder, such as Huffman or Arithcoding.
--
SaSW, Willem
No.4 | | 349 bytes | |
Delta encoding. Encode the difference from the previous number:
)

Hm Where is that kind of "encoding" useful? I guess it doesn't really
"compress" the given input ?

If your source consists of 8bit values and the deltas can be represented by
7bits, then you have indeed compressed the input.

Andy
No.5 | | 512 bytes | |
)Delta encoding. Encode the difference from the previous number:
))

stdazi wrote:
) Hm Where is that kind of "encoding" useful? I guess it doesn't really
) "compress" the given input ?

I've already given the answer to that, quoted below for your convenience:

)As you can see, lower numbers occur a lot more than higher numbers in this
)series. You can take advantage of this by using some kind of entropy
)encoder, such as Huffman or Arithcoding.

SaSW, Willem
No.6 | | 115 bytes | |
thanks guy's never thought about the delta encoding! that's just what I
was needing

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