Programmer Guide/General Descriptions/Segment Expressions: Difference between revisions
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{{STX}} uses a special syntax to address a segment of a sound file. The syntax allows for the mixed use of segment names and time values in a complex expression known as a "segment expression". Segment expressions can be used in all commands and dialogs where a signal segment (or position/duration) can be specified (exceptions are described in the Command Reference). In dialogs, the supported value formats/types are always described in the control/dialog caption. | {{STX}} uses a special syntax to address a segment of a sound file. The syntax allows for the mixed use of segment names and time values in a complex expression known as a "segment expression". Segment expressions can be used in all commands and dialogs where a signal segment (or position/duration) can be specified (exceptions are described in the Command Reference). In dialogs, the supported value formats/types are always described in the control/dialog caption. | ||
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|labelexpression_<nowiki>-</nowiki>labelexpression | |labelexpression_<nowiki>-</nowiki>labelexpression | ||
|(end and duration) | |(end and duration) | ||
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The segment expression <var>segexpr</var> specifies a label (position) in a signal or a segment (part) of a signal. The command evaluates the segment expression and returns the label position or the begin, end and length of the segment. | |||
:{|class="einrahmen" | |||
!<var>segexpr</var> !! description | |||
|- | |||
|<code>''bexpr''</code> || a position (label) at ''bexpr'' | |||
|- | |||
|<code>''bexpr''_''eexpr</code> || a segment with begin ''bexpr'' and end ''expr'' | |||
|- | |||
|<code>''bexpr''_+''lexpr''</code> || a segment with begin ''bexpr'' and length ''lexpr'' (end = ''bexpr''+''lexpr'') | |||
|- | |||
|<code>''eexpr''_-''lexpr''</code> || a segment with end ''eexpr'' and length ''lexpr'' (begin = ''eexpr''-''lexpr'') | |||
|} | |||
Each part (''bexpr'', ''eexpr'' and ''lexpr'') of the segment expression specifies a time in samples and may consist of one or more time values which are joined with the operator '''+''' (add) or '''-''' (subtract). | |||
:{|class="einrahmen" | |||
!value !!description !!value in samples !!comment | |||
|- | |||
|<var>x</var> ||<var>x</var> samples ||<var>x</var> || | |||
|- | |||
|<var>x</var>'''s''' ||<var>x</var> seconds ||<var>x</var> * ''sr'' || | |||
|- | |||
|<var>x</var>'''ms''' ||<var>x</var> milliseconds ||<var>x</var> / 1000 * ''sr'' || | |||
|- | |||
|<var>x</var>'''Hz''' ||periode of a signal with <var>x</var> Hz ||''sr'' / <var>x</var> || | |||
|- | |||
|<var>x</var>'''kHz''' ||periode of a signal with <var>x</var> kHz ||''sr'' / (<var>x</var> * 1000) || | |||
|- | |||
|<var>x</var>'''%''' ||<var>x</var> percent of the signal length ||''l'' * <var>x</var> / 100 ||usage 1 and 2 only | |||
|- | |||
|<var>x</var>'''%%''' ||<var>x</var> per mill of the signal length ||''l'' * <var>x</var> / 1000 ||usage 1 and 2 only | |||
|- | |||
|<var>segid</var> ||begin and length of the segment with id <var>segid</var> || ||usage 3 only | |||
|- | |||
|<var>segid</var>''':b''' ||begin of the segment with id <var>segid</var> || ||usage 3 only | |||
|- | |||
|<var>segid</var>''':e''' ||end of the segment with id <var>segid</var> || ||usage 3 only | |||
|- | |||
|<var>segid</var>''':l''' ||length of the segment with id <var>segid</var> || ||usage 3 only | |||
|- | |||
|} | |||
:{|class="keinrahmen" | |||
|with: ||<var>x</var>||=||a number | |||
|- | |||
| ||''sr''||=||signal sampling rate in Hz | |||
|- | |||
| ||''l''||=||signal length in samples (e.g. soundfile length) | |||
|- | |||
| ||''segid''||=||id of a segment defined in the xml-file item | |||
|} | |} | ||
Revision as of 20:00, 28 April 2014
STx uses a special syntax to address a segment of a sound file. The syntax allows for the mixed use of segment names and time values in a complex expression known as a "segment expression". Segment expressions can be used in all commands and dialogs where a signal segment (or position/duration) can be specified (exceptions are described in the Command Reference). In dialogs, the supported value formats/types are always described in the control/dialog caption.
Labels
A label expression is a position in a sound file (e.g. the begin/end of a segment) or the duration of a segment. A label expression may consist of a sign (+/-) and one or more values formatted as described below and combined with the operators + (add) or – (subtract). If a label expression contains blanks, it must be quoted when used as an argument.
| label expression | explanation |
| segmentname:B | start time of segment segmentname |
| segmentname:E | end time of segment segmentname |
| segmentname:L | duration (length) of segment segmentname |
| numberS | time in seconds |
| numberMS | time in milliseconds |
| number | number of samples |
Segments
A segment expression addresses a part of a soundfile with a non-zero duration. It can consist of (1) a segment name or (2) two label expressions specifying the beginning and end or (3) two label expressions specifying a position and the duration.
| segment expression | explanation |
| labelexpression_labelexpression | (beginning and end) |
| labelexpression_+labelexpression | (beginning and duration) |
| labelexpression_-labelexpression | (end and duration) |
The segment expression segexpr specifies a label (position) in a signal or a segment (part) of a signal. The command evaluates the segment expression and returns the label position or the begin, end and length of the segment.
segexpr description bexpra position (label) at bexpr bexpr_eexpra segment with begin bexpr and end expr bexpr_+lexpra segment with begin bexpr and length lexpr (end = bexpr+lexpr) eexpr_-lexpra segment with end eexpr and length lexpr (begin = eexpr-lexpr)
Each part (bexpr, eexpr and lexpr) of the segment expression specifies a time in samples and may consist of one or more time values which are joined with the operator + (add) or - (subtract).
value description value in samples comment x x samples x xs x seconds x * sr xms x milliseconds x / 1000 * sr xHz periode of a signal with x Hz sr / x xkHz periode of a signal with x kHz sr / (x * 1000) x% x percent of the signal length l * x / 100 usage 1 and 2 only x%% x per mill of the signal length l * x / 1000 usage 1 and 2 only segid begin and length of the segment with id segid usage 3 only segid:b begin of the segment with id segid usage 3 only segid:e end of the segment with id segid usage 3 only segid:l length of the segment with id segid usage 3 only
with: x = a number sr = signal sampling rate in Hz l = signal length in samples (e.g. soundfile length) segid = id of a segment defined in the xml-file item
Examples
0_4s
addresses 0 samples to 4 seconds
SegmentA:B+100_+10s
addresses 100 samples after the beginning of SegmentB for a duration of 10 seconds
SegmentB
addresses SegmentB
SegmentA:B_SegmentB:E
addresses the beginning of SegmentA to the end of SegmentB
SegmentB:E_-100ms
addresses 100 milliseconds before the end of SegmentB to the end of SegmentB
Notes: For some expressions, the values number% (percentage of the full duration) and number%% (thousandths of the full duration) can be used, but only if the 'full signal' is available/defined (e.g. for envelopes of sequence signals).A segmentname can only be used if a sound file or an audio-element of an XML-file is involved in the expression evaluation.Segment names are case sensitive!
