Questions tagged [data-compression]
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180
questions
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1answer
36 views
Is a complete code always optimal?
According to wikipedia, Kraft's inequality holds with equality when a code is complete. Huffman encoding produces a complete code that is optimal. Are all complete codes optimal and vice versa?
-1
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2answers
46 views
Can data be compressed through this hash function technique?
I'd like to know if this data compression scheme would work or not, and why:
Suppose we have a file. If we treat the bits that make up the file as the binary representation of a number n, we have n (...
3
votes
0answers
32 views
Modifying the JPEG compression to use custom block patterns
recently, while watching a video about machine learning, I had an idea about creating an image compression algorithm, that works similar to JPEG, but is based on arbitrary bitmaps as blocks.
I should ...
1
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0answers
29 views
Implementing binary arithmetic encoder
I have set integers that are normally distributed, and I'm trying to implement binary arithmetic encoding, as suggested in this post: Compressing normally distributed data
I'm running into trouble ...
1
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1answer
27 views
How to find optimal token set for compression?
By token I mean the smallest element of source data, that the compression algorithm works on. It may be a bit (like in DMC), a letter (like in Huffman or PPM), a word, or variable-length string (like ...
0
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2answers
38 views
is there a (FLAC like) loseless compression coding format for EEG data? [closed]
EEG and Audio data are very similar, both
are numerical samples in continuous sequence
have a sample rate
need and can have multiple channels
channels for multi-channel audio
channels for each ...
1
vote
1answer
41 views
Run Length Encoding Compression With Nested Level
I am studying about some compression methods, and I'm very interested in RLE Algorithms. But are there any Nested-Level RLE methods, such as:
ABABABCABABABC --> 3(AB)C3AB(C) --> 2(3(AB)C) ?
It's ...
0
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0answers
35 views
Is entropy a good indicator of the quality of a lossy compression?
Say I want to quantitively evaluate the effectiveness of several color-to-grayscale conversion algorithms, which can be considered as lossy compression. Would entropy be a good indicator?
To ...
1
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1answer
33 views
Question is about a paper “A Block-sorting Lossless Data Compression Algorithm” by M. Burrows and D.J. Wheeler
In the paper A Block-sorting Lossless Data Compression Algorithm by M. Burrows and D.J. Wheeler Link.
On page number 5. please describe this line
If the original string $S$ is of the form $Z^p$ for ...
0
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0answers
42 views
An interesting compression algorithm idea
I stumbled on this paper about compressing images using a kind of odd, but interesting idea. It seems pretty easy to implement and I was wondering if there is something wrong with it that I haven't ...
0
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1answer
43 views
Coding for data compression with large target's symbol set (where the target symbol set is larger than the source symbol set)
For data compression, every codding that I've seen is binary. It means we convert a language with $N$ symbol size to a language with $M=2$ symbol size. For example, in Huffman coding, the goal is to ...
4
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1answer
699 views
How does a predictive coding aid in lossless compression?
I'm working on this lab where we need to apply a lossless predictive coding to an image before compressing it (with Huffman, or some other lossless compression algorithm).
From the example seen ...
0
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1answer
52 views
Is it possible to achieve greater than perfect compression using machine learning and big data?
Imagine Google wanted to make their chrome browser faster. Let "database" be all the machines which serve content from Google's servers, including Search and Google cloud services. Google begins using ...
3
votes
3answers
993 views
Algorithm to convert a fixed-length string to the smallest possible collision-free representation?
I have a US-based telephone number (in the format 000-000-0000) and need to convert it to a "shorter" representation. Using base32/64 produces too long of a string. I've discovered CRC-16, which ...
1
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0answers
35 views
Computing (near) optimal displacement tables
Suppose we have a two-dimensional table $T$ with $r$ rows and $c$ columns that is sparse. Let $T[i][j]$ be the element at the $i$th row and $j$th column of $T$, with zero-based indexing.
We can ...
34
votes
6answers
7k views
Do lossless compression algorithms reduce entropy?
According to Wikipedia:
Shannon's entropy measures the information contained in a message as opposed to the portion of the message that is determined (or predictable). Examples of the latter ...
2
votes
1answer
34 views
Is there an algorithm to achieve optimal compression in a “streamed” manner, assuming equal probability of each possibility?
(Sorry for the question title; edits are welcome.)
Let's say that you have a set of data made of repeating units, consisting of a value with $2$ possibilities, a value with $3$ possibilities, $5$ ...
2
votes
1answer
44 views
what is a shearlet/shearlet transform and how can i use it?
from what wikipedia says shearlet is a successor to wavelets(whatever that is) and that they are extremely good at representing complicated data efficiently. But neither wikipedia nor other articles ...
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3answers
202 views
I think you can always compress compressed data, is it true?
In compressed data, repetition of same pattern is not a lot, so, you can expect it to be with space inside to contain always. I found a way to compress data without limitation. Is it right? Am I ...
3
votes
1answer
153 views
What is the best way to compress a string with only numbers and commas in it?
I have a string like this:
11,512,64,23,46,12,67,85,84
And I'm sure it's following these rules below:
Only , and ...
2
votes
1answer
67 views
Compression algorithms for small strings - building upon / extending Huffman
I'm exploring algorithms to compress small strings like the following - every line is to be compressed individually, i.e. even those small strings should get compressed:
...
16
votes
4answers
5k views
Can data be compressed to size smaller than Shannon data compression limit?
I was reading about data compression algorithms and the theoretical limit for data compression. Recently I encountered a compression method called "Combinatorial Entropy Encoding", the main idea of ...
0
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1answer
92 views
What is the most compact (space efficient) method of storing an array of distinct integers?
I have an array of distinct integers which I want to save in the most compact manner. I may have to do occasional lookups, deletions, and insertions in this array so the compression algorithm must ...
6
votes
1answer
154 views
Most space-efficient lossy dictionary?
Short version: What is the most space-efficient lossy dictionary (with given false positive and false negative rates)?
Long version: A lossy dictionary is a data structure $D$ that encodes a set $S$ ...
2
votes
1answer
51 views
Algorithm for estimating lossless compression factor
Is there any algorithm for estimating how well certain array of bytes could be compressed in lossless manner?
Usage for me is to automatically choose "best" data reorder method without knowing what ...
2
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2answers
70 views
Does this progressive image compression exists?
I want to know if this progressive image compression that I have in mind exists and it it does I want know its name and/or get some references about it.
The algorithm consists of converting one high ...
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1answer
31 views
Character in Huffman encoding [closed]
Is a full stop regarded as a character along or must it be with a space in huffman encoding. I know of taking a comma with a space to a character.
1
vote
1answer
34 views
Compression with random dictionary
Is the following scenario theoretically possible, or provably impossible?
Alice generates a 1 GiB file with random bits and sends it to Bob. This file is a shared dictionary they call Q. Now, Alice ...
1
vote
0answers
24 views
Attribute Selection for minimum number of clusters
I have a table consisting of some headers $P, Q, R, S$ (shown in blue in Table 1). According to the headers, the column $T$ is populated using some predefined logic.
Now, any of the headers $P,Q,R,S$ ...
1
vote
2answers
67 views
Data compression with Turing Machine
For traditional algorithms compressed data may vary, while decompression algorithm is always the same. Are there any approaches, when (de)compression algorithm is also changing to provide best ...
0
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0answers
28 views
How much data can be send in 1 minute of audio with Smartphone speakers / microphones?
Having the current news about Google Assistant in mind, I thought that robots might use interfaces designed for humans to send data. Like a telephone interface.
Then I wondered: What is the maximum ...
0
votes
0answers
57 views
What algorithm is most suitable for large text compression?
Currently, I am looking for an lossless compression algorithm that is suitable for a large amount of text, that will be further encrypt by AES and use as the payload in steganography.
Based on A ...
2
votes
2answers
198 views
How would the use of an external lookup table affect file compression?
It occurred to me that, the way compression essentially works, is that you have a mapping of long patterns to short patterns, which you replace one way to compress and the other to decompress. My ...
1
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1answer
113 views
Was my Huffman coding solution wrong?
I finished my exam a moment ago and one of the question was to calculate Huffman coding for given probabilities:
A: 0.15
B: 0.2
C: 0.55
D: 0.1
I encoded them as ...
1
vote
1answer
50 views
Generate numeric or string ID for a sequence of elements
How to generate a numeric or string id(not very large text) for a sequence of elements where ordering doesn't matter.
Example:
[41,1001,32] should generate the ...
2
votes
1answer
38 views
Methods, Routines, or Algorithms To Optimize Selection of String Compression Methods
When encoding a a 2D Datamatrix barcode, I want the smallest output size. There are means to encode a compressed a string using some methods like C40.
Reference:
Here's a reference: https://en....
1
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3answers
112 views
Is there a method to compress all data without loss (lossless compression)?
I know that the answer is no but I'm not sure why. Here's where I started. We know that all data with length $n$ Bits and minimum $1$ Bit can be compressed, either lossless or lossy. But how do I ...
1
vote
1answer
91 views
Problem with determining the shape and direction of the Huffman Diagram
I have the phrase "abracadabra" and I want to encode it through the Huffman method. I first took the frequencies of each letters;
$$a=5$$
$$b=3$$
$$c=1$$
$$d=2$$
$$r=2$$
But I'm not sure as to how the ...
0
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1answer
61 views
Intuitive way to understand “Run-Length Encoding”
Run-Length Encoding is the simple form of lossless data compression in which compression in which runs (execution) of data are stored as a single data value and count rather than as the original run (...
24
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11answers
9k views
Is von Neumann's randomness in sin quote no longer applicable?
Some chap said the following:
Anyone who attempts to generate random numbers by deterministic means is, of course, living in a state of sin.
That's always taken to mean that you can't generate ...
0
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0answers
71 views
Is it possible for a [futuristic] computer to contain the information of the whole universe?
(This is a question of information theory, data compression and entropy, so I believe it fits CS forum)
Does the fact that the computer itself is a part of the universe make it logically impossible ...
2
votes
1answer
159 views
monotonically increasing codeword length in optimal (maybe Huffman) code for alphabet with monotonically decreasing frequencies
I'm working on exercise 16.3-5 of CLRS:
Prove that if we order the characters in an alphabet so that their frequencies are monotonically decreasing, then there exists an optimal code whose codeword ...
1
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0answers
35 views
Using less Random Access Memory
Suppose you were to compress data before it was sent to Random Access Memory. Wouldn't you technically be using less R.A.M?
3
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2answers
307 views
Representation of used space and free space in hard drives
I've read from this How data is physically stored in hard drives, that the North/South orientation of the magnetic medium represents data as 0 or 1 physically in the hard drive. Data is stored in ...
1
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1answer
34 views
What is the Code2 and other concepts of variable encoding in Coding Redundancy?
Am learning the concept of Coding Redundancy in image compression and am finding it hard to understand the table on page 3 of this document. All other explanations seem to follow the same symbols and ...
4
votes
1answer
234 views
Is there a limit to data compression without mentioning Kolmogorov complexity?
I want to develop a previous answer to Is there a known maximum for how much a string of 0's and 1's can be compressed?.
I've looked at the Hutter Prize and various compression benchmarks. The ...
0
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1answer
202 views
Universal Lossless Compression? [closed]
It is not possible to losslessly compress all files of size $n$ using a single algorithm, as there are more files of size $n (2^n)$ than of size $p, p: p < n ( 2^n-1)$. Via the pigeon hole ...
1
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1answer
130 views
Practicality of compressing data with hashing algorithms
I want to compress the string 0cc175b9c0f1b6a831c399e269772661. I can do so by storing the string a, and, when decompressing, using a as input for the MD5 hash algorithm to get the original string.
I ...
1
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0answers
113 views
Compression of gaussian variables
Say I have 2 Gaussian sources X and Y. They are generated with mutivariate gaussian distribution with ...
1
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0answers
82 views
Which algorithms provide high compression ratios for bit matrices?
I have an x*y bit matrix where the total number of bits fluctuates between ~1,000,000 and ~20,000,000 bits. The rows are much smaller than the columns. An example matrix might be of size 1,000,000 x ...
