+++ /dev/null
-The audio file selector
-=======================
-
-Paraslash comes with a sophisticated audio file selector called *afs*.
-In the
-<<
-<a href="INSTALL.html">installation notes</a>,
->>
-only the "dummy" mode of afs was used which gets activated automatically if
-nothing else was specified. In this section the various features of afs are
-described.
-
-----------
-Attributes
-~~~~~~~~~~
-
-An attribute is simply a bit which can be set for each audio
-file individually. Up to 64 different attributes may be
-defined. For example, "pop", "rock", "blues", "jazz", "instrumental",
-"german_lyrics", "speech", whatever. It's up to you how many attributes
-you define and how you call them.
-
-A new attribute "test" is created by
-
- para_client addatt test
-and
- para_client lsatt
-
-lists all available attributes. You can set the "test" attribute for
-an audio file by executing
-
- para_client setatt test+ /path/to/the/audio/file
-
-Similarly, the "test" bit can be removed from an audio file with
-
- para_client setatt test- /path/to/the/audio/file
-
-Instead of a path you may use a shell wildcard pattern. The attribute
-is applied to all audio files matching that pattern:
-
- para_client setatt test+ '/test/directory/*'
-
-The command
-
- para_client -- ls -lv
-
-gives you a verbose listing of your audio files which contains also
-which attributes are set.
-
-In case you wonder why the double-dash in the above command is needed:
-It tells para_client to not interpret the options after the dashes. If
-you find this annoying, just say
-
- alias para='para_client --'
-
-and be happy. In what follows we shall use this alias.
-
-The "test" attribute can be dropped from the database with
-
- para rmatt test
-
-Read the output of
-
- para help ls
- para help setatt
-
-for more information and a complete list of command line options to
-these commands.
-
-
-----------------------
-Abstract mood nonsense
-~~~~~~~~~~~~~~~~~~~~~~
-
-[skip this part if you don't like formal definitions]
-
-A mood consists of a unique name and its *mood definition*, which is
-a set of *mood lines* containing expressions in terms of attributes
-and other data contained in the database.
-
-A mood defines a subset of audio files called the *admissible audio files*
-for that mood. At any time, at most one mood can be *active* which
-means that para_server is going to select only files from that subset
-of admissible files.
-
-So in order to create a mood definition one has to write a set of
-mood lines. Mood lines come in three flavours: Accept lines, deny
-lines and score lines.
-
-The general syntax of the three types of mood lines is
-
-
- accept [with score <score>] [if] [not] <mood_method> [options]
- deny [with score <score>] [if] [not] <mood_method> [options]
- score <score> [if] [not] <mood_method> [options]
-
-
-Here <score> is either an integer or the string "random" which assigns
-a random score to all matching files. The score value changes the
-order in which admissible files are going to be selected, but is of
-minor importance for this introduction.
-
-So we concentrate on the first two forms, i.e. accept and deny
-lines. As usual, everything in square brackets is optional, i.e.
-accept/deny lines take the following form when ignoring scores:
-
- accept [if] [not] <mood_method> [options]
-
-and analogously for the deny case. The "if" keyword is purely cosmetic
-and has no function. The "not" keyword just inverts the result, so
-the essence of a mood line is the mood method part and the options
-following thereafter.
-
-A *mood method* is realized as a function which takes an audio file
-and computes a number from the data contained in the database.
-If this number is non-negative, we say the file *matches* the mood
-method. The file matches the full mood line if it either
-
- - matches the mood method and the "not" keyword is not given,
-or
- - does not match the mood method, but the "not" keyword is given.
-
-The set of admissible files for the whole mood is now defined as those
-files which match at least one accept mood line, but no deny mood line.
-More formally, an audio file F is admissible if and only if
-
- (F ~ AL1 or F ~ AL2...) and not (F ~ DL1 or F ~ DN2 ...)
-
-where AL1, AL2... are the accept lines, DL1, DL2... are the deny
-lines and "~" means "matches".
-
-The cases where no mood lines of accept/deny type are defined need
-special treatment:
-
- - Neither accept nor deny lines: This treats all files as admissible
- (in fact, that is the definition of the dummy mood which is activated
- automatically if no moods are available).
-
- - Only accept lines: A file is admissible iff it matches at least one
- accept line:
-
- F ~ AL1 or F ~ AL2 or ...
-
- - Only deny lines: A file is admissible iff it matches no deny line:
-
- not (F ~ DL1 or F ~ DN2 ...)
-
-
-
---------------------
-List of mood_methods
-~~~~~~~~~~~~~~~~~~~~
-
- no_attributes_set
-
-Takes no arguments and matches an audio file if and only if no
-attributes are set.
-
- is_set <attribute_name>
-
-Takes the name of an attribute and matches iff that attribute is set.
-
- path_matches <pattern>
-
-Takes a filename pattern and matches iff the path of the audio file
-matches the pattern.
-
- artist_matches <pattern>
- album_matches <pattern>
- title_matches <pattern>
- comment_matches <pattern>
-
-Takes an extended regular expression and matches iff the text of the
-corresponding tag of the audio file matches the pattern. If the tag
-is not set, the empty string is matched against the pattern.
-
- year ~ <num>
- bitrate ~ <num>
- frequency ~ <num>
- channels ~ <num>
- num_played ~ <num>
-
-Takes a comparator ~ of the set {<, =, <=, >, >=, !=} and a number
-<num>. Matches an audio file iff the condition <val> ~ <num> is
-satisfied where val is the corresponding value of the audio file
-(value of the year tag, bitrate in kbit/s, frequency in Hz, channel
-count, play count).
-
-The year tag is special as its value is undefined if the audio file
-has no year tag or the content of the year tag is not a number. Such
-audio files never match. Another difference is the special treatment
-if the year tag is a two-digit number. In this case either 1900 or
-2000 are added to the tag value depending on whether the number is
-greater than 2000 plus the current year.
-
-
-----------
-Mood usage
-~~~~~~~~~~
-
-To create a new mood called "my_mood", write its definition into
-some temporary file, say "tmpfile", and add it to the mood table
-by executing
-
- para addmood my_mood < tmpfile
-
-If the mood definition is really short, you may just pipe it to the
-client instead of using temporary files. Like this:
-
- echo "$MOOD_DEFINITION" | para addmood my_mood
-
-There is no need to keep the temporary file since you can always use
-the catmood command to get it back:
-
- para catmood my_mood
-
-A mood can be activated by executing
-
- para select m/my_mood
-
-Once active, the list of admissible files is shown by the ls command
-if the "-a" switch is given:
-
- para ls -a
-
------------------------
-Example mood definition
-~~~~~~~~~~~~~~~~~~~~~~~
-
-Suppose you have defined attributes "punk" and "rock" and want to define
-a mood containing only Punk-Rock songs. That is, an audio file should be
-admissible if and only if both attributes are set. Since
-
- punk and rock
-
-is obviously the same as
-
- not (not punk or not rock)
-
-(de Morgan's rule), a mood definition that selects only Punk-Rock
-songs is
-
- deny if not is_set punk
- deny if not is_set rock
-
-
----------
-Troubles?
----------
-
-Use the debug loglevel (option -l debug for most commands) to show
-debugging info. Almost all paraslash executables have a brief online
-help which is displayed by using the -h switch. The --detailed-help
-option prints the full help text.
-
-If para_server crashed or was killed by SIGKILL (signal 9), it
-may refuse to start again because of "dirty osl tables". In this
-case you'll have to run the oslfsck program of libosl to fix your
-database. It might be necessary to use --force (even if your name
-isn't Luke). However, make sure para_server isn't running before
-executing oslfsck --force.
-
-If you don't mind to recreate your database you can start
-from scratch by removing the entire database directory, i.e.
-
- rm -rf ~/.paraslash/afs_database-0.4
-
-Be aware that this removes all attribute definitions, all playlists
-and all mood definitions.
-
-Although oslfsck fixes inconsistencies in database tables it doesn't
-care about the table contents. To check for invalid table contents, use
-
- para_client check
-
-This prints out references to missing audio files as well as invalid
-playlists and mood definitions.
-
-Still having problems? mailto: Andre Noll <maan@systemlinux.org>
projects / paraslash.git / blobdiff