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bieliqus 17-10-2018 06:00

Compressing other files
 
Hello

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). If so can anybody give me a hint what should i look into first? There are so many methods and tutorials here that is hard to know from which i should start with.

Sorry for noob question but i'm just starting my adventure with archives.

Thanks

Joe Forster/STA 17-10-2018 13:08

Quote:

Originally Posted by bieliqus (Post 476391)
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.

kj911 10-10-2021 04:23

MJPEG video recompression
 
See testing now: https://encode.su/threads/3716-MJPEG...-recompression

Compression rate ~1/3 size than original. Really?? Very likely fast and XP SP3 compatible MJPEG lossless video recompression tools. (Like Ocarina's 0.6 MPEG-2 recompressor.)

small test from XP use AVI.exe and precomp. (scanmjpeg.exe and splitmjpg.exe don't work.)

Source: ANIM0346.AVI
Size: 82 770 846 byte

CMD command: AVI.exe ANIM0346.AVI
Generated RAW file: video.mp3
Size: 74 912 294 byte

Crunching by Precomp 0.48 32bit (KPS version)
CMD command: precomp048.32.exe -cn video.mp3
Output PCF file size: 62 115 776 byte

Precomp results:
Time: 50 second(s), 344 millisecond(s)

Recompressed streams: 2180/2180
JPG streams: 2180/2180


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