uharc

The following quotes are from the program documentation.

-m0..3 Set compression mode.

• -m0 Store files without compression.
• -m1 Use ALZ:1 (fast) compression mode.
• -m2 Use ALZ:2 (norm) compression mode.
• -m3 Use ALZ:3 (best) compression mode.
• -mx Use PPM compression mode.
• -mz Use LZP compression mode.

ALZ uses advanced LZ77 compression algorithm with arithmetic entropy coder. "-m1" is the fastest ALZ mode, sacrificing compression ratio to gain better speed. Mode "-m3" achieves best compression and needs most time. "-m2" is a compromise ratio/speed and is used as default mode. The decompression speed is nearly the same for all ALZ modes and it is much faster than compression.

PPM mode uses an order-4-2-1-0 model with preliminary LZP pass. In most cases this mode provides the best compression results.

LZP mode uses the same dictionary compression as in PPM mode but with much simpler order-1-0 literal model.

There are also two extra modes (may be not supported in future versions):

• -mr Use simple RLE compression.
• -mw Use LZ78 with selectable dictionary size.

-md Set maximum dictionary size (in KB).

If dictionary is disabled, this setting has no effect. Valid sizes:

• -m1..3,-mx,-mz n = power of 2 from 1 to 32768 or "a".."p"
• -mw n = power of 2 from 1 to 32 or "a".."f"

A one-character shortcut can be used instead of size number, e.g. "-mda" instead of "-md1" or "-mdk" instead of "-md1024".

Dictionary size selection:

1. Using option "-mdn", UHARC will never select a dictionary size greater than n. If "-mdn" is not used, UHARC will try to use default dictionary (n=4096).
2. If data stream size is smaller than n, UHARC will use the smallest dictionary size which is greater than the data stream.
3. If there is not enough memory for current selection, UHARC will use the largest dictionary size which is possible with available memory.

-mm[-,+] Disable/enable built-in multimedia detection/compression.

• -mm[+] Enable multimedia detection/compression.
• -mm- Disable multimedia detection/compression.

UHARC multimedia detection/compression supports many data types (8/16-bit mono/stereo waveforms, 24-bit true color pictures and many other types using 8/16/24/32-bit record sizes). It's also possible to detect multimedia-like data in other file types (e.g. in executables). Therefore it's NOT RECOMMENDED to disable multimedia detection/compression unless the user knows, that there is absolutely no chance to use multimedia compression (e.g. compressing text only).

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