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2<HTML>
3<HEAD>
4 <META http-equiv="Content-Type" content="text/html; charset=Windows-1252">
5 <TITLE>-m (Set compression Method) switch</TITLE>
6 <LINK href="style.css" rel="stylesheet" type="text/css">
7</HEAD>
8
9<BODY>
10
11<H1>-m (Set compression Method) switch</H1>
12
13<P>Specifies the compression method.</P>
14
15<H4>Syntax</H4>
16
17<PRE class="syntax">
18-m&lt;method_parameters>
19
20</PRE>
21
22<P>The format for this switch depends on the archive type.</P>
23
24<UL>
25<LI><TD><A class="parameter" href="#Zip">Zip</A></TD>
26<LI><TD><A class="parameter" href="#GZ">GZip</A></TD>
27<LI><TD><A class="parameter" href="#BZ2">BZip2</A></TD>
28<LI><TD><A class="parameter" href="#7Z">7z</A></TD>
29<LI><TD><A class="parameter" href="#XZ">XZ</A></TD>
30</UL>
31
32<H2><A name="Zip"></A>Zip</H2>
33<TABLE>
34 <TR>
35 <TH width="160">Parameter</TH>
36 <TH align="center">Default</TH>
37 <TH>Description</TH> </TR>
38 <TR>
39 <TD><A class="parameter" href="#ZipX">x=[0 | 1 | 3 | 5 | 7 | 9 ]</A></TD>
40 <TD align="center">5</TD>
41 <TD>Sets level of compression.</TD> </TR>
42 <TR>
43 <TD>m={MethodID}</TD>
44 <TD align="center">Deflate</TD>
45 <TD>Sets a method: Copy, Deflate, Deflate64, BZip2, LZMA, PPMd.</TD> </TR>
46 <TR>
47 <TD><A class="parameter" href="#Deflate_FastBytes">fb={NumFastBytes}</A></TD>
48 <TD align="center">32</TD>
49 <TD>Sets number of Fast Bytes for Deflate encoder.</TD> </TR>
50 <TR>
51 <TD><A class="parameter" href="#Zip_Pass">pass={NumPasses}</A></TD>
52 <TD align="center">1</TD>
53 <TD>Sets number of Passes for Deflate encoder.</TD></TR>
54 <TR>
55 <TD><A class="parameter" href="#ZipDictionarySize">d={Size}[b|k|m]</A></TD>
56 <TD align="center">900000</TD>
57 <TD>Sets Dictionary size for BZip2</TD></TR>
58 <TR>
59 <TD><A class="parameter" href="#ZipMemorySize">mem={Size}[b|k|m]</A></TD>
60 <TD align="center">24</TD> <TD>Sets size of used memory for PPMd.</TD></TR>
61 <TR>
62 <TD><A class="parameter" href="#ZipOrder">o={Size}</A></TD>
63 <TD align="center">8</TD> <TD>Sets model order for PPMd.</TD></TR>
64 <TR>
65 <TD><A class="parameter" href="#ZipMultiThread">mt=[off | on | {N}]</A></TD>
66 <TD align="center">on</TD>
67 <TD>Sets multithreading mode.</TD></TR>
68 <TR>
69 <TD>em={EncryptionMethodID}</TD>
70 <TD align="center">ZipCrypto</TD>
71 <TD>Sets a encryption method: ZipCrypto, AES128, AES192, AES256</TD> </TR>
72 <TR> <TD><A class="parameter">tc=[off | on]</A></TD>
73 <TD align="center">off</TD> <TD>Stores NTFS timestamps for files: Modification time, Creation time, Last access time.</TD> </TR>
74 <TR> <TD><A class="parameter">cl=[off | on]</A></TD>
75 <TD align="center">off</TD> <TD>7-Zip always uses local code page for file names.</TD> </TR>
76 <TR> <TD><A class="parameter">cu=[off | on]</A></TD>
77 <TD align="center">off</TD> <TD>7-Zip uses UTF-8 for file names that contain non-ASCII symbols.</TD> </TR>
78</TABLE>
79
80<P>By default (if <B>cl</B> and <B>cu</B> switches are not specified), 7-Zip uses UTF-8 encoding
81only for file names that contain symbols unsupported by local code page.</P>
82
83<DL>
84 <DT><A name="ZipX"></A>x=[0 | 1 | 3 | 5 | 7 | 9 ]</DT>
85 <DD>
86 <P>Sets level of compression. x=0 means Copy mode (no compression).</P>
87 <P>Deflate / Deflate64 settings:</P>
88 <TABLE>
89 <TR> <TH>Level</TH> <TH>NumFastBytes</TH> <TH>NumPasses</TH> <TH>Description</TH> </TR>
90 <TR> <TD class="cc">1</TD> <TD class="cc" rowspan=3>32</TD> <TD class="cc" rowspan=3>1</TD> <TD>Fastest</TD> </TR>
91 <TR> <TD class="cc">3</TD> <TD>Fast</TR>
92 <TR> <TD class="cc">5</TD> <TD>Normal</TR>
93 <TR> <TD class="cc">7</TD> <TD class="cc">64</TD> <TD class="cc">3</TD> <TD>Maximum</TD> </TR>
94 <TR> <TD class="cc">9</TD> <TD class="cc">128</TD> <TD class="cc">10</TD> <TD>Ultra</TD> </TR>
95 </TABLE>
96
97 <P>x=1 and x=3 with Deflate method set fast mode for compression.</P>
98
99 <P>BZip2 settings:</P>
100 <TABLE>
101 <TR> <TH>Level</TH> <TH>Dictionary</TH> <TH>NumPasses</TH> <TH>Description</TH> </TR>
102 <TR> <TD class="cc">1</TD> <TD class="cc">100000</TD> <TD class="cc" rowspan=3>1</TD> <TD>Fastest</TD> </TR>
103 <TR> <TD class="cc">3</TD> <TD class="cc">500000</TD> <TD>Fast</TD> </TR>
104 <TR> <TD class="cc">5</TD> <TD class="cc" rowspan=3>900000</TD> <TD>Normal</TD> </TR>
105 <TR> <TD class="cc">7</TD> <TD align="center">2</TD> <TD>Maximum</TD> </TR>
106 <TR> <TD class="cc">9</TD> <TD align="center">7</TD> <TD>Ultra</TD> </TR>
107 </TABLE>
108 </DD>
109
110 <DT><A name="Deflate_FastBytes"></A>fb={NumFastBytes}</DT>
111 <DD>
112 <P>Sets the number of fast bytes for the Deflate/Deflate64 encoder.
113 It can be in the range from 3 to 258 (257 for Deflate64).
114 Usually, a big number gives a little bit better
115 compression ratio and a slower compression process.
116 A large fast bytes parameter can significantly increase the compression ratio
117 for files which contain long identical sequences of bytes.</P>
118 </DD>
119 <DT><A name="Zip_Pass"></A>pass={NumPasses}</DT>
120 <DD>
121 <P>Sets number of passes for Deflate encoder. It can be in the range from 1 to 15 for Deflate and
122 from 1 to 10 for BZip2. Usually, a big number gives a little bit better
123 compression ratio and a slower compression process.
124 </P>
125 </DD>
126 <DT><A name="ZipDictionarySize"></A>d={Size}[b|k|m]</DT>
127 <DD>
128 <P> Sets the Dictionary size for BZip2. You must specify the size in bytes, kilobytes, or megabytes.
129 The maximum value for the Dictionary size is 900000b. If you do not specify any symbol
130 from set [b|k|m], dictionary size will be calculated as DictionarySize = 2^Size bytes.</P>
131 </DD>
132
133 <DT><A name="ZipMemorySize"></A>mem={Size}[b|k|m]</DT>
134 <DD>
135 <P> Sets the size of memory used for PPMd. You must specify the size in bytes, kilobytes, or megabytes.
136 The maximum value is 256 MB = 2^28 bytes. The default value
137 is 24 (16MB). If you do not specify any symbol from the set [b|k|m], the
138 memory size will be calculated as (2^Size) bytes. PPMd uses the same
139 amount of memory for compression and decompression.</P>
140 </DD>
141
142 <DT><A name="ZipOrder"></A>o={Size}</DT>
143 <DD>
144 <P>Sets the model order for PPMd. The size must be in the range [2,16]. The default value is 8.</P>
145 </DD>
146
147 <DT><A name="ZipMultiThread"></A>mt=[off | on | {N}]</DT>
148 <DD>
149 <P>Sets multithread mode. If you have a multiprocessor or multicore system,
150 you can get a speed increase with
151 this switch. This option affects only compression (with any method) and
152 decompression of BZip2 streams.
153 Each thread in the multithread mode uses 32 MB of RAM for buffering.
154 If you specify {N}, 7-Zip tries to use N threads.</P>
155 </DD>
156</DL>
157
158<H2><A name="GZ"></A>GZip</H2>
159GZip uses the same parameters as Zip, but GZip compresses only with Deflate method.
160So GZip supports only the following parameters: x, fb, pass.
161
162<H2><A name="BZ2"></A>BZip2</H2>
163<TABLE>
164 <TR>
165 <TH width="160">Parameter</TH>
166 <TH align="center">Default</TH>
167 <TH>Description</TH> </TR>
168 <TR>
169 <TD><A class="parameter" href="#BZip2X">x=[1 | 3 | 5 | 7 | 9 ]</A></TD>
170 <TD align="center">5</TD>
171 <TD>Sets level of compression.</TD> </TR>
172 <TR>
173 <TD><A class="parameter" href="#BZip2Pass">pass={NumPasses}</A></TD>
174 <TD align="center">1</TD>
175 <TD>Sets number of Passes for Bzip2 encoder.</TD></TR>
176 <TR>
177 <TD><A class="parameter" href="#BZip2DictionarySize">d={Size}[b|k|m]</A></TD>
178 <TD align="center">900000</TD>
179 <TD>Sets Dictionary size for BZip2</TD></TR>
180 <TR>
181 <TD><A class="parameter" href="#BZip2MultiThread">mt=[off | on | {N}]</A></TD>
182 <TD align="center">on</TD>
183 <TD>Sets multithreading mode.</TD></TR>
184</TABLE>
185
186<DL>
187 <DT><A name="BZip2"></A>x=[1 | 3 | 5 | 7 | 9 ]</DT>
188 <DD>
189 <P>Sets level of compression</P>
190 <TABLE>
191 <TR> <TH>Level</TH> <TH>Dictionary</TH> <TH>NumPasses</TH> <TH>Description</TH> </TR>
192 <TR> <TD class="cc">1</TD> <TD class="cc">100000</TD> <TD class="cc" rowspan=3>1</TD> <TD>Fastest</TD> </TR>
193 <TR> <TD class="cc">3</TD> <TD class="cc">500000</TD> <TD>Fast</TD> </TR>
194 <TR> <TD class="cc">5</TD> <TD class="cc" rowspan=3>900000</TD> <TD>Normal</TD> </TR>
195 <TR> <TD class="cc">7</TD> <TD align="center">2</TD> <TD>Maximum</TD> </TR>
196 <TR> <TD class="cc">9</TD> <TD align="center">7</TD> <TD>Ultra</TD> </TR>
197 </TABLE>
198 </DD>
199
200 <DT><A name="BZip2DictionarySize"></A>d={Size}[b|k|m]</DT>
201 <DD>
202 <P> Sets the Dictionary size for BZip2. You must specify the size in bytes, kilobytes, or megabytes.
203 The maximum value for the Dictionary size is 900000b. If you do not specify any symbol
204 from set [b|k|m], dictionary size will be calculated as DictionarySize = 2^Size bytes.</P>
205 </DD>
206
207 <DT><A name="#BZip2Pass"></A>pass={NumPasses}</DT>
208 <DD>
209 <P>Sets the number of passes. It can be in the range from 1 to 10.
210 The default value is 1 for normal mode, 2 for maximum mode and 7 for ultra mode.
211 A bigger number can give a little bit better compression ratio and a slower compression process.
212 </P>
213 </DD>
214 <DT><A name="BZip2MultiThread"></A>mt=[off | on | {N}]</DT>
215 <DD>
216 <P>Sets multithread mode. If you have a multiprocessor or multicore system,
217 you can get a speed increase with
218 this switch. If you specify {N}, for example mt=4, 7-Zip tries to use 4 threads.</P>
219 </DD>
220</DL>
221
222<H2><A name="7Z"></A>7z</H2>
223<TABLE>
224 <TR> <TH width="80">Parameter</TH> <TH align="center">Default</TH> <TH>Description</TH> </TR>
225 <TR> <TD><A class="parameter" href="#SevenZipX">x=[0 | 1 | 3 | 5 | 7 | 9 ]</A></TD>
226 <TD align="center">5</TD><TD>Sets level of compression.</TD> </TR>
227 <TR> <TD><A class="parameter" href="#Solid">s=[off | on | [e] [{N}f] [{N}b | {N}k | {N}m | {N}g]</A></TD>
228 <TD align="center">on</TD> <TD>Sets solid mode.</TD> </TR>
229 <TR> <TD><A class="parameter" href="#Filter">f=[off | on]</A></TD>
230 <TD align="center">on</TD> <TD>Enables or disables compression filters for executable files.</TD> </TR>
231 <TR> <TD><A class="parameter" href="#HeaderCompress">hc=[off | on]</A></TD>
232 <TD align="center">on</TD> <TD>Enables or disables archive header compressing.</TD> </TR>
233 <TR> <TD><A class="parameter" href="#HeaderEncrypt">he=[off | on]</A></TD>
234 <TD align="center">off</TD> <TD>Enables or disables archive header encryption.</TD> </TR>
235 <TR> <TD><A class="parameter" href="#Bind">b{C1}[s{S1}]:{C2}[s{S2}]</A></TD>
236 <TD align="center"> </TD> <TD>Sets binding beetwen coders.</TD> </TR>
237 <TR> <TD><A class="parameter" href="#MethodID">{N}={MethodID}[:param1][:param2][..]</A></TD>
238 <TD align="center">LZMA</TD> <TD>Sets a method: LZMA, LZMA2, PPMd, BZip2, Deflate, Delta, BCJ, BCJ2, Copy.</TD> </TR>
239 <TR> <TD><A class="parameter" href="#MultiThread">mt=[off | on | {N}]</A></TD>
240 <TD align="center">on</TD> <TD>Sets multithreading mode.</TD> </TR>
241 <TR> <TD><A class="parameter">tc=[off | on]</A></TD>
242 <TD align="center">off</TD> <TD>Stores file creation timestamps.</TD> </TR>
243</TABLE>
244
245<DL>
246 <DT><A name="SevenZipX"></A>x=[0 | 1 | 3 | 5 | 7 | 9 ]</DT>
247 <DD>
248 <P>Sets level of compression</P>
249 <TABLE>
250 <TR> <TH>Level</TH> <TH>Method</TH> <TH>Dictionary</TH> <TH>FastBytes</TH> <TH>MatchFinder</TH> <TH>Filter</TH> <TH>Description</TH> </TR>
251 <TR> <TD align="center">0</TD> <TD align="center">Copy</TD> <TD align="center"></TD> <TD align="center"></TD> <TD align="center"></TD> <TD align="center"></TD> <TD>No compression.</TD> </TR>
252 <TR> <TD align="center">1</TD> <TD align="center">LZMA</TD> <TD align="center">64 KB</TD> <TD align="center">32</TD> <TD align="center">HC4</TD> <TD align="center">BCJ</TD> <TD>Fastest compressing</TD> </TR>
253 <TR> <TD align="center">3</TD> <TD align="center">LZMA</TD> <TD align="center">1 MB</TD> <TD align="center">32</TD> <TD align="center">HC4</TD> <TD align="center">BCJ</TD> <TD>Fast compressing</TD> </TR>
254 <TR> <TD align="center">5</TD> <TD align="center">LZMA</TD> <TD align="center">16 MB</TD> <TD align="center">32</TD> <TD align="center">BT4</TD> <TD align="center">BCJ</TD> <TD>Normal compressing</TD> </TR>
255 <TR> <TD align="center">7</TD> <TD align="center">LZMA</TD> <TD align="center">32 MB</TD> <TD align="center">64</TD> <TD align="center">BT4</TD> <TD align="center">BCJ</TD> <TD>Maximum compressing</TD> </TR>
256 <TR> <TD align="center">9</TD> <TD align="center">LZMA</TD> <TD align="center">64 MB</TD> <TD align="center">64</TD> <TD align="center">BT4</TD> <TD align="center">BCJ2</TD><TD>Ultra compressing</TD> </TR>
257 </TABLE>
258 <P>Note: "x" works as "x=9".</P>
259 </DD>
260
261 <DT><A name="Solid"></A>s=[off | on | [e] [{N}f] [{N}b | {N}k | {N}m | {N}g)]</DT>
262 <DD>
263 <P> Enables or disables solid mode. The default mode is s=on.
264 In solid mode, files are grouped together. Usually, compressing in
265 solid mode improves the compression ratio.</P>
266
267 <TABLE>
268 <TR> <TD>e</TD> <TD>Use a separate solid block for each new file extension</TD> </TR>
269 <TR> <TD>{N}f</TD> <TD>Set the limit for number of files in one solid block</TD> </TR>
270 <TR> <TD>{N}b | {N}k | {N}m | {N}g</TD> <TD>Set a limit for the total size of a solid block in bytes</TD> </TR>
271 </TABLE>
272
273 <P>These are the default limits for the solid block size:</P>
274
275 <TABLE>
276 <TR> <TH width="150">Compression Level</TH> <TH>Solid block size</TH> </TR>
277 <TR> <TD>Store</TD> <TD>0 B</TD> </TR>
278 <TR> <TD>Fastest</TD> <TD>16 MB</TD> </TR>
279 <TR> <TD>Fast</TD> <TD>128 MB</TD> </TR>
280 <TR> <TD>Normal</TD> <TD>2 GB</TD> </TR>
281 <TR> <TD>Maximum</TD> <TD>4 GB</TD> </TR>
282 <TR> <TD>Ultra</TD> <TD>4 GB</TD> </TR>
283 </TABLE>
284
285
286 <P>Limitation of the solid block size usually decreases compression ratio but gives the following advantages:</P>
287 <UL>
288 <LI>Decreases losses in case of future archive damage.
289 <LI>Decreases extraction time of a group of files (or just one
290 file), so long as the group doesn't contain the entire archive.</LI></LI>
291 </UL>
292 <P>The updating of solid .7z archives can be slow, since it
293 can require some recompression.</P>
294
295 <P>Example:</P>
296 <PRE class="example">
297 s=100f10m
298 </PRE>
299 <P>set solid mode with 100 files & 10 MB limits per one solid block.</P>
300
301 <DT><A name="Filter"></A>f=[off | on]</DT>
302 <DD>
303 <P>Enables or disables compression filters for executable files:
304 dll, exe, ocx, sfx, sys. It uses BCJ2 filter in Ultra mode and BCJ
305 filter in other modes. The default mode is f=on.
306 </P>
307 <DT><A name="HeaderCompress"></A>hc=[off | on]</DT>
308 <DD>
309 <P> Enables or disables archive header compressing. The default mode is hc=on.
310 If archive header compressing is enabled, some parts of archive header will
311 be compressed with LZMA method.
312 </P>
313 <DT><A name="HeaderEncrypt"></A>he=[off | on]</DT>
314 <DD>
315 <P> Enables or disables archive header encryption. The default mode is he=off.
316 </P>
317 <DT>{N}</DT>
318 <DD>
319 <P>Sets order of methods. It is used also to associate parameters with
320 methods. Numbers must begin from 0. Methods that have smaller numbers will be used
321 before others.</P>
322 </DD>
323
324 <DT><A name="Bind"></A>b{C1}[s{S1}]:{C2}[s{S2}]</DT>
325 <DD>
326 <P> Binds output stream S1 in coder C1 with input stream S2 in coder C2.
327 If stream number is not specified, stream with number 0 will be used.
328 </P>
329 <P> Usally coder has one input stream and
330 one output stream. In 7z some coders can have multiple input and output streams.</P>
331
332 <P>For example, <A class="parameter" href="#BCJ2">BCJ2</A> encoder has one
333 input stream and four output streams.</P>
334 </DD>
335
336 <DT><A name="MultiThread"></A>mt=[off | on | {N}]</DT>
337 <DD>
338 <P>Sets multithread mode. If you have a multiprocessor or multicore system,
339 you can get a increase with this switch.
340 7-Zip supports multithread mode only for LZMA / LZMA2 compression and
341 BZip2 compression / decompression. If you specify {N}, for example mt=4,
342 7-Zip tries to use 4 threads. LZMA compression uses only 2 threads.
343 </P>
344 </DD>
345
346 <DT><A name="MethodID"></A>{N}={MethodID}[:param1][:param2] ... [:paramN]</DT>
347 <DD>
348 <P>Sets compression method. You can use any number of methods.
349 The default method is LZMA. </P>
350 <P>Parameters must be in one of the following forms:</P>
351 <UL>
352 <LI>{ParamName}={ParamValue}.
353 <LI>{ParamName}{ParamValue}, if {ParamValue}
354 is number and {ParamName} doesn't contain numbers.
355 </UL>
356
357 <P>Supported methods:</P>
358 <TABLE>
359 <TR> <TH width="60">MethodID</TH> <TH>Description</TH> </TR>
360 <TR> <TD><A class="parameter" href="#LZMA">LZMA</A></TD> <TD>LZ-based algorithm</TD> </TR>
361 <TR> <TD><A class="parameter" href="#LZMA2">LZMA2</A></TD> <TD>LZMA-based algorithm</TD> </TR>
362 <TR> <TD><A class="parameter" href="#PPMd">PPMd</A></TD> <TD>Dmitry Shkarin's PPMdH with small changes</TD> </TR>
363 <TR> <TD>BZip2</TD> <TD>BWT algorithm</TD> </TR>
364 <TR> <TD>Deflate</TD> <TD>LZ+Huffman</TD> </TR>
365 <TR> <TD>Copy</TD> <TD>No compression</TD> </TR>
366 </TABLE>
367
368 <P>Supported filters:</P>
369 <TABLE>
370 <TR> <TH width="60">MethodID</TH> <TH>Description</TH> </TR>
371 <TR> <TD><A class="parameter" href="#Delta">Delta</A></TD> <TD>Delta filter</TD> </TR>
372 <TR> <TD>BCJ</TD> <TD>converter for x86 executables</TD> </TR>
373 <TR> <TD><A class="parameter" href="#BCJ2">BCJ2</A></TD> <TD>converter for x86 executables (version 2)</TD> </TR>
374 <TR> <TD>ARM</TD> <TD>converter for ARM (little endian) executables</TD> </TR>
375 <TR> <TD>ARMT</TD> <TD>converter for ARM Thumb (little endian) executables</TD> </TR>
376 <TR> <TD>IA64</TD> <TD>converter for IA-64 executables</TD> </TR>
377 <TR> <TD>PPC</TD> <TD>converter for PowerPC (big endian) executables</TD> </TR>
378 <TR> <TD>SPARC</TD> <TD>converter for SPARC executables</TD> </TR>
379 </TABLE>
380 <P>Filters increase the compression ratio for some types of files. Filters
381 must be used with one of the compression method (for example, BCJ + LZMA).</P>
382 </DD>
383
384 <H4><A name="LZMA"></A>LZMA</H4>
385 <P> LZMA is an algorithm based on Lempel-Ziv algorithm.
386 It provides very fast decompression (about 10-20 times faster than compression).
387 Memory requirements for compression and decompression also are different (see
388 <A class="parameter" href="#DictionarySize">d={Size}[b|k|m]</A> switch for details).</P>
389
390 <TABLE>
391 <TR> <TH width="80">Parameter</TH> <TH align="center">Default</TH> <TH>Description</TH> </TR>
392
393 <TR> <TD><A class="parameter" href="#LZMAMode">a=[0|1]</A></TD>
394 <TD align="center">1</TD> <TD>Sets compressing mode</TD> </TR>
395 <TR> <TD><A class="parameter" href="#DictionarySize">d={Size}[b|k|m]</A></TD>
396 <TD align="center">24</TD> <TD>Sets Dictionary size</TD> </TR>
397 <TR> <TD><A class="parameter" href="#MatchFinder">mf={MF_ID}</A></TD>
398 <TD align="center">bt4</TD> <TD>Sets Match Finder</TD> </TR>
399 <TR> <TD><A class="parameter" href="#FastBytes">fb={N}</A></TD>
400 <TD align="center">32</TD> <TD>Sets number of Fast Bytes</TD></TR>
401 <TR> <TD><A class="parameter" href="#MatchFinderCycles">mc={N}</A></TD>
402 <TD align="center">32</TD><TD>Sets Number of Cycles for Match Finder</TD> </TR>
403 <TR> <TD><A class="parameter" href="#LitContext">lc={N}</A></TD>
404 <TD align="center">3</TD> <TD>Sets number of Literal Context bits - [0, 8]</TD></TR>
405 <TR> <TD><A class="parameter" href="#LitPos">lp={N}</A></TD>
406 <TD align="center">0</TD> <TD>Sets number of Literal Pos bits - [0, 4]</TD></TR>
407 <TR> <TD><A class="parameter" href="#PosBits">pb={N}</A></TD>
408 <TD align="center">2</TD> <TD>Set number of Pos Bits - [0, 4]</TD></TR>
409 </TABLE>
410
411
412 <DL>
413 <DT><A name="#LZMAMode"></A>a=[0|1]</DT>
414 <DD>
415 <P> Sets compression mode: 0 = fast, 1 = normal.
416 Default value is 1.</P>
417 </DD>
418 <DT><A name="DictionarySize"></A>d={Size}[b|k|m]</DT>
419 <DD>
420 <P> Sets Dictionary size for LZMA. You must specify the size in bytes, kilobytes, or megabytes.
421 The maximum value for dictionary size is 1 GB = 2^30 bytes. Default values for LZMA
422 are 24 (16 MB) in normal mode, 25 (32 MB) in maximum mode (-mx=7)
423 and 26 (64 MB) in ultra mode (-mx=9).
424 If you do not specify any symbol from the set [b|k|m], the
425 dictionary size will be calculated as DictionarySize = 2^Size bytes.
426 For decompressing a file compressed by LZMA method with dictionary size N, you need
427 about N bytes of memory (RAM) available.
428 </P>
429 </DD>
430 <DT><A name="MatchFinder"></A>mf={MF_ID}</DT>
431 <DD>
432 <P> Sets Match Finder for LZMA. Default method is bt4.
433 Algorithms from hc* group don't provide a good compression ratio,
434 but they often work pretty fast in combination with fast mode (a=0).
435 Memory requirements depend on dictionary size (parameter "d" in table below).
436 </P>
437 <TABLE>
438 <TR> <TH>MF_ID</TH> <TH class="cc">Dictionary</TH> <TH class="cc" colspan = 2>Memory Usage</TH> <TH class="cc" colspan = 2>Description</TH> </TR>
439 <TR> <TD class="cc">bt2</TD> <TD></TD> <TD align="right"> 9.5 * d</TD> <TD class="cc" rowspan=6> + 4 MB</TD> <TD class="cc" rowspan=4>Binary Tree</TD> <TD>2 bytes hashing</TD> </TR>
440 <TR> <TD class="cc">bt3</TD> <TD></TD> <TD align="right">11.5 * d</TD> <TD>3 bytes hashing</TD> </TR>
441 <TR> <TD class="cc" rowspan=2>bt4</TD> <TD class="cc">64 KB ... 48 MB</TD> <TD align="right">11.5 * d</TD> <TD class="cc" rowspan=6>4 bytes hashing</TD> </TR>
442 <TR> <TD class="cc">64 MB ... 1024 MB</TD> <TD align="right">10.5 * d</TD> </TR>
443 <TR> <TD class="cc" rowspan=2>hc4</TD> <TD class="cc">64 KB ... 48 MB</TD> <TD align="right"> 7.5 * d</TD> <TD class="cc" rowspan=2>Hash Chain </TD></TR>
444 <TR> <TD class="cc">64 MB ... 1024 MB</TD> <TD align="right"> 6.5 * d</TD> </TR>
445 </TABLE>
446 <P>Note: Your operation system also needs some amount of physical memory for internal purposes.
447 So keep at least 32MB of physical memory unused.</P>
448 </DD>
449
450 <DT><A name="FastBytes"></A>fb={N}</DT>
451 <DD>
452 <P>Sets number of fast bytes for LZMA. It can be in the range from 5 to 273.
453 The default value is 32 for normal mode and 64 for maximum and ultra modes.
454 Usually, a big number gives a little bit better
455 compression ratio and slower compression process.
456 </P>
457 </DD>
458 <DT><A name="MatchFinderCycles"></A>mc={N}</DT>
459 <DD>
460 <P>Sets number of cycles (passes) for match finder. It can be in range from 0 to 1000000000.
461 Default value is (16 + number_of_fast_bytes / 2) for BT* match finders and
462 (8 + number_of_fast_bytes / 4) for HC4 match finder.
463 If you specify mc=0, LZMA will use default value.
464 Usually, a big number gives a little bit better compression ratio and slower
465 compression process. For example, mf=HC4 and mc=10000 can provide almost the same
466 compression ratio as mf=BT4.</P>
467 </DD>
468 <DT><A name="LitContext"></A>lc={N}</DT>
469 <DD>
470 <P>Sets the number of literal context bits (high bits of previous literal).
471 It can be in range from 0 to 8.
472 Default value is 3. Sometimes lc=4 gives gain for big files.</P>
473 </DD>
474 <DT><A name="LitPos"></A>lp={N}</DT>
475 <DD>
476 <P>Sets the number of literal pos bits (low bits of current position for literals).
477 It can be in the range from 0 to 4.
478 The default value is 0. The lp switch is intended for periodical data when the
479 period is equal to 2^value (where lp=value). For example, for 32-bit (4 bytes)
480 periodical data you can use lp=2. Often it's better to set lc=0,
481 if you change lp switch.</P>
482 </DD>
483 <DT><A name="PosBits"></A>pb={N}</DT>
484 <DD>
485 <P>Sets the number of pos bits (low bits of current position).
486 It can be in the range from 0 to 4.
487 The default value is 2. The pb switch is intended for periodical data when the
488 period is equal 2^value (where lp=value). </P>
489 </DD>
490
491 </DL>
492
493 <H4><A name="LZMA2"></A>LZMA2</H4>
494 <P>LZMA2 is modified version of LZMA. it provides the following advantages over LZMA:</P>
495 <UL>
496 <LI>Better compression ratio for data than can't be compressed. LZMA2 can store such
497 blocks of data in uncompressed form. Also it decompresses such data faster.
498 <LI>Better multithreading support. If you compress big file, LZMA2 can split
499 that file to chunks and compress these chunks in multiple threads.
500 </UL>
501
502 <TABLE>
503 <TR> <TH width="80">Parameter</TH> <TH align="center">Default</TH> <TH>Description</TH> </TR>
504
505 <TR> <TD><A class="parameter" href="#ChunkSize">c={Size}[b|k|m]</A></TD>
506 <TD align="center">dictSize * 4</TD> <TD>Sets Chunk size</TD> </TR>
507 </TABLE>
508
509 <P>If you don't specify ChunkSize, LZMA2 sets it to DictionarySize * 4.</P>
510
511 <P>LZMA2 also supports all LZMA parameters, but lp+lc cannot be larger than 4.</P>
512
513 <P>LZMA2 uses: 1 thread for each chunk in x1 and x3 modes; and
514 2 threads for each chunk in x5, x7 and x9 modes.
515 If LZMA2 is set to use only such number of threads required for one chunk,
516 it doesn't split stream to chunks. So you can get different compression
517 ratio for different number of threads. You can get the best compression
518 ratio, when you use 1 or 2 threads.</P>
519
520 <H4><A name="PPMd"></A>PPMd</H4>
521 <P> PPMd is a PPM-based algorithm. This algorithm is mostly based
522 on Dmitry Shkarin's PPMdH source code. PPMd provides very good compression ratio for
523 plain text files. There is no difference between compression speed and
524 decompression speed. Memory requirements for compression and decompression
525 also are the same.</P>
526 <TABLE>
527 <TR> <TH width="80">Parameter</TH> <TH align="center">Default</TH> <TH>Description</TH> </TR>
528 <TR> <TD><A class="parameter" href="#MemorySize">mem={Size}[b|k|m]</A></TD>
529 <TD align="center">24</TD> <TD>Sets size of used memory for PPMd.</TD> </TR>
530 <TR> <TD><A class="parameter" href="#Order">o={Size}</A></TD>
531 <TD align="center">6</TD> <TD>Sets model order for PPMd.</TD> </TR>
532 </TABLE>
533 <DL>
534 <DT><A name="MemorySize"></A>mem={Size}[b|k|m]</DT>
535 <DD>
536 <P> Sets the size of memory used for PPMd. You must specify the size in bytes, kilobytes, or megabytes.
537 The maximum value is 2GB = 2^31 bytes. The default value
538 is 24 (16MB). If you do not specify any symbol from the set [b|k|m], the
539 memory size will be calculated as (2^Size) bytes. PPMd uses the same
540 amount of memory for compression and decompression.</P>
541 </DD>
542
543 <DT><A name="Order"></A>o={Size}</DT>
544 <DD>
545 <P>Sets the model order for PPMd. The size must be in the range [2,32]. The default value is 6.</P>
546 </DD>
547 </DL>
548
549 <H4><A name="BCJ2"></A>BCJ2</H4>
550 <P>BCJ2 is a Branch converter for 32-bit x86 executables (version 2).
551 It converts some branch instructions for increasing further compression.</P>
552 <P>A BCJ2 encoder has one input stream and four output streams:</P>
553 <UL>
554 <LI>s0: main stream. It requires further compression.</LI>
555 <LI>s1: stream for converted CALL values. It requires further compression.</LI>
556 <LI>s2: stream for converted JUMP values. It requires further compression.</LI>
557 <LI>s3: service stream. It is already compressed.</LI>
558 </UL>
559 <P>If LZMA is used, the size of the dictionary for streams
560 s1 and s2 can be much smaller (512 KB is enough for most cases)
561 than the dictionary size for stream s0.</P>
562
563 <H4><A name="Delta"></A>Delta</H4>
564 <P>It's possible to set delta offset in bytes. For example, to compress 16-bit stereo
565 WAV files, you can set "0=Delta:4". Default delta offset is 1.</P>
566</DL>
567
568<H2><A name="XZ"></A>XZ</H2>
569XZ supports only LZMA2 codec now. The switches are similar to switches for 7z format.
570
571<H4>Examples</H4>
572
573<PRE class="example">
5747z a -tzip archive.zip *.jpg -mx0
575</PRE>
576
577<P>adds <SPAN class="filename">*.jpg</SPAN> files to
578 <SPAN class="filename">archive.zip</SPAN> archive without compression.</P>
579
580<PRE class="example">
5817z a -t7z archive.7z *.exe *.dll -m0=BCJ -m1=LZMA:d=21 -ms -mmt
582</PRE>
583
584<P>adds <SPAN class="filename">*.exe</SPAN> and <SPAN class="filename">*.dll</SPAN>
585files to solid archive <SPAN class="filename">archive.7z</SPAN> using LZMA method with
5862 MB dictionary and BCJ converter. Compression will use multithreading optimization.</P>
587
588<PRE class="example">
5897z a -t7z archive.7z *.exe *.dll -m0=BCJ2 -m1=LZMA:d23 -m2=LZMA:d19 -m3=LZMA:d19
590 -mb0:1 -mb0s1:2 -mb0s2:3
591</PRE>
592
593<P>adds <SPAN class="filename">*.exe</SPAN> and <SPAN class="filename">*.dll</SPAN>
594 files to archive <SPAN class="filename">archive.7z</SPAN> using BCJ2 converter,
595 LZMA with 8 MB dictionary for main output stream (s0),
596 and LZMA with 512 KB dictionary for s1 and s2 output streams of BCJ2.</P>
597
598
599<PRE class="example">
6007z a -t7z archive.7z *.txt -m0=PPMd
601</PRE>
602
603<P>adds <SPAN class="filename">*.txt</SPAN> files to archive
604<SPAN class="filename">archive.7z</SPAN> using PPMd method.</P>
605
606
607
608
609<H4>Commands that can be used with this switch</H4>
610
611<P>
612 <A href="../commands/add.htm">a (Add)</A>,
613 <A href="../commands/delete.htm">d (Delete)</A>,
614 <A href="../commands/update.htm">u (Update)</A>,
615</P>
616
617<H4>See also</H4>
618
619<P>
620 <B>Switches:</B>
621 <A href="type.htm">-t (set Type of archive)</A>,
622</P>
623
624</BODY>
625</HTML>
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