paraslash 0.3.1
[paraslash.git] / README.afs
1 The audio file selector
2 =======================
3
4 Paraslash comes with a sophisticated audio file selector called afs.
5 In the
6 <<
7 <a href="INSTALL.html">installation notes</a>,
8 >>
9 only the "dummy" mode of afs was used which gets activated automatically if
10 nothing else was specified. In this section the various features of afs are
11 described.
12
13 ----------
14 Attributes
15 ~~~~~~~~~~
16
17 An attribute is simply a bit which can be set for each audio
18 file individually. Up to 64 different attributes may be
19 defined. For example, "pop", "rock", "blues", "jazz", "instrumental",
20 "german_lyrics", "speech", whatever. It's up to you how many attributes
21 you define and how you call them.
22
23 A new attribute "test" is created by
24
25 para_client addatt test
26 and
27 para_client lsatt
28
29 lists all available attributes. You can set the "test" attribute for
30 an audio file by executing
31
32 para_client setatt test+ /path/to/the/audio/file
33
34 Similarly, the "test" bit can be removed from a audio file with
35
36 para_client setatt test- /path/to/the/audio/file
37
38 Instead of a path you can also use a pattern, and the attribute is
39 applied to all audio files matching that pattern:
40
41 para_client setatt test+ '/test/directory/*'
42
43 The command
44
45 para_client -- ls -lv
46
47 gives you a verbose listing of your audio files which contains also
48 which attributes are set.
49
50 In case you wonder why the double-dash in the above command is needed:
51 It tells para_client to not interpret the options after the dashes. If
52 you find this annoying, just say
53
54 alias para='para_client --'
55
56 and be happy. In the remainder part this alias is being used.
57
58 Drop the test attribute entirely from the database with
59
60 para rmatt test
61
62 Read the output of
63
64 para help ls
65 para help setatt
66
67 for more information and a complete list of command line options to
68 these commands.
69
70
71 ----------------------
72 Abstract mood nonsense
73 ~~~~~~~~~~~~~~~~~~~~~~
74
75 [skip this part if you don't like formal definitions]
76
77 A mood consists of a unique name and its *mood definition*, which is a set of
78 *mood lines* containing expressions in terms of attributes and other data
79 contained in the database.
80
81 A mood defines a subset of audio files called the *admissible audio files*
82 for that mood. A mood can be *active* which means that para_server
83 is going to select only files from that subset of admissible files.
84
85 So in order to create a mood definition one has to write a set of
86 mood lines. Mood lines come in three flavours: Accept lines, deny
87 lines and score lines.
88
89 The general syntax of the three types of mood lines is
90
91
92 accept [with score <score>] [if] [not] <mood_method> [options]
93 deny [with score <score>] [if] [not] <mood_method> [options]
94 score <score> [if] [not] <mood_method> [options]
95
96
97 Here <score> is either an integer or the string "random" which assigns
98 a random score to all matching files. The score value changes the
99 order in which admissible files are going to be selected, but is of
100 minor importance for this introduction.
101
102 So we concentrate on the first two forms, that is accept and deny
103 lines. As usual, everything in square brackets is optional, i.e.
104 accept/deny lines take the following form when ignoring scores:
105
106 accept [if] [not] <mood_method> [options]
107
108 and analogously for the deny case. The "if" keyword is purely cosmetic
109 and has no function. The "not" keyword just inverts the result, so
110 the essence of a mood line is the mood method part and the options
111 following thereafter.
112
113 A *mood method* is realized as a function which takes an audio file
114 and computes a number from the data contained in the database.
115 If this number is non-negative, we say the file *matches* the mood
116 method. The file matches the full mood line if it either
117
118 - matches the mood method and the "not" keyword is not given,
119 or
120 - does not match the mood method, but the "not" keyword is given.
121
122 The set of admissible files for the whole mood is now defined as those
123 files which match at least one accept mood line, but no deny mood line.
124 More formally, a file is admissible if and only if
125
126 (F ~ AL1 or F ~ AL2...) and not (F ~ DL1 or F ~ DN2 ...)
127
128 where F is the file, AL1, AL2... are the accept lines, DL1, DL2... are
129 the deny lines and "~" means "matches".
130
131 The cases where no mood lines of accept/deny type are defined need
132 special treatment:
133
134 - Neither accept nor deny lines: This treats all files as admissible
135 (in fact, that is the definition of the dummy mood which is activated
136 automatically if no moods are available).
137
138 - Only accept lines: A file is admissible iff it matches at least one
139 accept line:
140
141 F ~ AL1 or F ~ AL2 or ...
142
143 - Only deny lines: A file is admissible iff it matches no deny line:
144
145 not (F ~ DL1 or F ~ DN2 ...)
146
147
148
149 --------------------
150 List of mood_methods
151 ~~~~~~~~~~~~~~~~~~~~
152
153 no_attributes_set
154
155 Takes no arguments and matches an audio file if and only if no
156 attributes are set.
157
158 played_rarely
159
160 Takes no arguments and matches all audio files where the number of
161 times this audio file was selected is below the average.
162
163 is_set attribute_name
164
165 Takes the name of an attribute and matches iff that attribute is set.
166
167 path_matches pattern
168
169 Takes a filename pattern and matches iff the path of the audio file
170 matches the pattern.
171
172
173 ----------
174 Mood usage
175 ~~~~~~~~~~
176
177 To create a new mood called "my_mood", write its definition into
178 some temporary file, say "tmpfile", and add it to the mood table
179 by executing
180
181 para addmood my_mood < tmpfile
182
183 If the mood definition is really short, you may just pipe it to the
184 client instead of using temporary files. Like this:
185
186 echo "$MOOD_DEFINITION" | para addmood my_mood
187
188 There is no need to keep the temporary file since you can always use
189 the catmood command to get it back:
190
191 para catmood my_mood
192
193 A mood can be activated by executing
194
195 para chmood my_mood
196
197 Once active, the list of admissible files is shown by the ls command
198 if the "-a" switch is given:
199
200 para ls -a
201
202 -----------------------
203 Example mood definition
204 ~~~~~~~~~~~~~~~~~~~~~~~
205
206 Suppose you have defined attributes "punk" and "rock" and want to define
207 a mood containing only Punk-Rock songs. That is, an audio file should be
208 admissible if and only if both attributes are set. Since
209
210 punk and rock
211
212 is obviously the same as
213
214 not (not punk or not rock)
215
216 (de Morgan's rule), a mood definition that selects only Punk-Rock
217 songs is
218
219 deny if not is_set punk
220 deny if not is_set rock
221
222
223 ---------
224 Troubles?
225 ---------
226
227 Use loglevel one (option -l 1 for most commands) to show debugging
228 info. Almost all paraslash executables have a brief online help which
229 is displayed by using the -h switch.
230
231 para_fsck tries to fix your database. Use --force (even if your name
232 isn't Luke), to clean up after a crash. However, first make sure
233 para_server isn't running before executing para_fsck if para_fsck
234 complains about busy (dirty) tables. para_fsck also contains an option
235 to dump the contents of your the contents of the database to the file
236 system.
237
238 If you don't mind to recreate your database you can start
239 from scratch by removing the entire database directory, i.e.
240
241 rm -rf ~/.paraslash/afs_database
242
243 Note that this removes all tables, in particular attribute definitions
244 and data, and all playlist and mood definitions.
245
246 para_fsck operates on the osl-layer, i.e. it fixes inconsistencies
247 in the database but doesn't know about the contents of the tables
248 contained therein. Use
249
250 para_client check
251
252 to print out bad entries, e.g.missing audio files or invalid mood
253 definitions.
254
255 Still having problems? mailto: Andre Noll <maan@systemlinux.org>