View Single Post
  #2  
Old 17-10-2018, 13:08
Joe Forster/STA's Avatar
Joe Forster/STA Joe Forster/STA is offline
Senior forum member
 
Join Date: Nov 2000
Location: Hungary
Posts: 9,706
Thanks: 10
Thanked 295 Times in 186 Posts
Joe Forster/STA is on a distinguished road
Quote:
Originally Posted by bieliqus View Post
I'm new to compression and i wonder if i can use game compression methods to compress other files like pdf or media (avi, jpg etc).
In general, the answer is "no". In particular, PDF and JPEG are old standards so they have to rely on old algorithms to remain compatible with files created years or decades ago.

PDF compression methods are:
- RLE (run length encoding);
- LZW (Lempel-Ziv-Welch, modified from Lempel & Ziv's original LZ77 [from 1977!]);
- deflate (gzip, zip; mostly LZ77 plus Huffman encoding).

JPEG:
- DCT (discrete cosine transformation; not a compression method in itself, it rather "smooths" the picture so that it can be compressed better; it also results in "artifacts", the loss of original fine details and emergence of fine details that weren't originally there);
- RLE;
- Huffman encoding or arithmetic coding.

AVI is not a compression method but a container format. You can put into it video and audio compressed, in theory, with any compression algorithm ("codec" = encoding/decoding). The codec's code ("FourCC" = four character code) is stored in the AVI header; upon reading this information, the player will have to decide how to decompress the video and audio. Common (not all!) AVI video codecs are: MPEG-4 (DivX, XviD), H.264 (MPEG-4 AVC) and MJPEG (Motion JPEG); common audio codes: MP3, AC3 and DTS.

Games, on the other hand, don't have to be compatible with anything else as they contain their own decompression algorithms. This algorithm can be the very latest, sometimes with bugs. Established standards can't afford that.
__________________
Joe Forster/STA
For more information, see the FileForums forum rules and the PC Games forum FAQ!
Don't contact me via E-mail or PM to ask for help with anything other than patches (or software in general) done by me, otherwise your request may be deleted without any reply!
Homepage: http://sta.c64.org, E-mail: [email protected]; for attachments, send compressed (ZIP or RAR) files only, otherwise your E-mail will bounce back!

Last edited by Joe Forster/STA; 17-10-2018 at 13:15.
Reply With Quote