I need to compress some spatially correlated data records. Currently I am getting 1.2x-1.5x compression with zlib, but I figure it should be possible to get more like 2x. The data records have various fields, but for example, zlib seems to have trouble compressing lists of points. The points represent a road network. They are pairs of f...
Is there a way for me to lossless compress text with the following characters(88 in total)? abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ123456789!@#$%&*()-_+=;:'"<,>.?/[]{} I am making a chat but I don't want it to be wasting so much bandwidth(an old chat I used a few hours wasted 800mb). The text would be compressed in java...
I am running some tests on audio compression and trying out Skype's Silk. In their test application I am seeing compression rates of 94%. This seems high, is this a typical rate on Silk? Is this comparable to other audio compression codecs? ...
Hello, I'm trying to make a small VBScript that compacts a MS Access 2007 database file. The code I have is: Set acc2007 = CreateObject("DAO.DBEngine.36") acc2007.CompactDatabase "C:\test.accdb", "C:\test2.accdb", Nothing, Nothing, ";pwd=test" Set acc2007 = Nothing I'm getting this error when I run the three lines with "cscript test.v...
Hi, I'd like to do some kind of "search and replace" algorithm which will, in an efficient manner if possible, identify a substring of a string which occurs more than once and replace all occurrences of that substring with a token. For example, given a string "AbcAdAefgAbijkAblmnAbAb", notice that "A" recurs, so reduce in pass one to "#...
I'm working on Scala with VERY larg lists of Int (maybe large) and I need to compress them and to hold it in memory. The only requirement is that I can pull (and decompress) the first number on the list to work with, whithout touching the rest of the list. I have many good ideas but most of them translate the numbers to bits. Example: ...
I have a dataset contained in a directory that has about 30,000 sub-directories. Each of these directories contains a text file and another sub-directory. This sub-directory contains some number of text files (ranging from 0 text files, to hundreds). Many of my colleagues use this dataset, but as it is it takes at least 6 hours to tra...
I have byte arrays that can be a few dozen megabytes in size. Such large arrays are not happy creatures, especially when you have a many of them. So I would like to compress them, so they're easier to deal with. They compress well, generally a 3:1 ratio with DotNetZip set to BestSpeed. The data in the arrays can be nearly identical. ...
Hi everyone, I have a problem: Given an array nxm that contains 0's or 1's, I need group the 0 values into rectangles. At the beginning, I was used a simple quadtree, but different nodes in the same level of the tree have the same value. I'm not totally sure if the R-tree works for my problem or another data structure because I just will...
I'm using UIImagePickerController to allow my user to select a video from the asset library. When the user selects the "Choose" button on the second screen, the view displays a progress bar and a "Compressing Video..." message. Why is this happening? Is there some way I can avoid this compression operation? ...
Please recommend a technology suitable for the following task. I have a rather big (500MB) data chunk, which is basically a matrix of numbers. The data entropy is low (it should be well-compressible) and the storage is expensive where it sits. What I am looking for, is to compress it with a good compression algorithm (Like, say, GZip)...
My company maintains a domain-specific language that syntactically resembles the Excel formula language. We're considering adding new builtins to the language. One way to do this is to identify verbose commands that are repeatedly used in our codebase. For example, if we see people always write the same 100-character command to trim whit...
In an effort to get better at programming assembly, and as an academic exercise, I would like to write a non-trivial program in x86 assembly. Since file compression has always been kind of an interest to me, I would like to write something like the zip utility in assembly. I'm not exactly out of my element here, having written a simple...
Hi Friends, I am stuck with this problem. We are doing compression in .net and decompression in iPhone, Using GZip compression on both sides but the answer differs. Anyone has clue then please reply. Thanks in Advance. ...
I'm looking for a Java compression library that: is good for XML has a small footprint is fast (rather than achieves high compression ratio - speed is more important) easy to use What do you guys suggest? Thanks ...
Hello, I want to merge 2 bzip2'ed files. I tried appending one to another: cat file1.bzip2 file2.bzip2 > out.bzip2 which seems to work (this file decompressed correctly), but I want to use this file as a Hadoop input file, and I get errors about corrupted blocks. What's the best way to merge 2 bzip2'ed files without decompressing them? ...
Just out of curiosity, does there exist a valid zip-file (according to format spec) that, contains nothing but itself? Put another way, does the function implemented by unzip have a fix-point? Can I write a program to search for such a fix-point in a intelligent (not-exhaustive) way? I've thought about the opposite as well, i.e. if zi...
I'm new to Java. I've been able to read a "raw" image file with short data, display it, and save it as a .jp2 file but the 150.000 byte file gets compressed to just over 50,000 bytes. Some years ago I used a propriatry library to in C/C++ to do this and achieved lossless compression of the same type of images in the range of 10:1. My ...
I have hundreds of CSV files zipped. This is great because they take very little space but when it is time to use them, I have to make some space on my HD and unzip them before I can process. I was wondering if it is possible with .NET to unzip a file while reading it. In other words, I would like to open a zip file, start to decompress...
Hi I am looking at my performance in yslow and even though I gzipped my css and js scripts it says I should gzip my html page. Compression reduces response times by reducing the size of the HTTP response. Gzip is the most popular and effective compression method currently available and generally reduces the response size b...