c++ - Data Compression Algorithms -


i wondering if has list of data compression algorithms. know nothing data compression , hoping learn more different algorithms , see ones newest , have yet developed on lot of asics.

i'm hoping implement data compression asic independent of type of data coming in (audio,video,images,etc.)

if question open ended, please let me know , i'll revise. thank you

there ton of compression algorithms out there. need here lossless compression algorithm. lossless compression algorithm compresses data such can decompressed achieve given before compression. opposite lossy compression algorithm. lossy compression can remove data file. png images use lossless compression while jpeg images can , use lossy compression.

some of known compression algorithms include:

zip archives use combination of huffman coding , lz77 give fast compression , decompression times and reasonably compression ratios.

lz77 pretty generalized form of rle , yield better results.

huffman allows repeating bytes represent least number of bits. imagine text file looked this:

aaaaaaaabbbbbcccdd

a typical implementation of huffman result in following map:

bits character    0           10         b  110         c 1110         d

so file compressed this:

00000000 10101010 10110110 11011101 11000000                                        ^^^^^                               padding bits required

18 bytes go down 5. of course, table must included in file. algorithm works better more data :p

alex allain has a nice article on huffman compression algorithm in case wiki doesn't suffice.

feel free ask more information. topic pretty darn wide.


Comments

Post a Comment

Popular posts from this blog

linux - xterm copying to CLIPBOARD using copy-selection causes automatic updating of CLIPBOARD upon mouse selection -

i've tried various ways coerce xterm (versions 285 , 292) copy selection clipboard clipboard whenever press ctrl-shift-c. promising way far has been, in ~/.xresources, put this: xterm*vt100.translations: #override \ ctrl shift <keypress> c: copy-selection(clipboard) \n\ ctrl shift <keypress> v: insert-selection(clipboard) ctrl-shift-v works perfectly, copying has nuance... if restart xterm, highlighting text puts things in primary clipboard; expected, proper, default behavior. if hit ctrl-shift-c, copies current selection clipboard clipboard. the bug, however, if highlight text after first time pressed ctrl-shift-c, you'll see highlighting copies both primary and clipboard. cannot figure out how stop xterm updating clipboard upon selection... , doesn't make sense me in first place. i said, @ specific point in time, copy selection clipboard... yet starts updating automatically upon selection after doing once... anyone have workaround...
Read more

c++ - qgraphicsview horizontal scrolling always has a vertical delta -

Image
i've subclassed qgraphicsview custom canvas used in cad application. i've reimplemented qgraphicsview::wheelevent check keyboard modifiers control key and, if control key pressed, zoom. i'm trying implement horizontal scroll when user holds shift , uses wheel. the problem i'm having horizontal scrolling always scrolls 0.279. not huge problem, hugely annoying , points else being wrong. so, here questions: is right way implement horizontal scrolling? if not, is? how eliminate delta of 0.279? thanks in advance. code , sample output below void myview::zoom(int delta) { double factor = pow(1.2, delta/abs(delta)); this->scale(factor, factor); } void myview::scrollhorizontal(int level) { qpointf center = maptoscene(viewport()->rect().center()); qdebug() << "center: " << center.x() << ", " << center.y(); centeron(qpointf(center.x() - level, center.y())); } void myview::wheelevent(qwheeleve...
Read more