Programmer Guide/Command Reference/SEGMENT: Difference between revisions
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:;<var>idattr, pattr, lattr</var>:the xml attributes used in the segment definition elements to specifiy the segment id (<var>idattr</var>) and its starting position (<var>pattr</var>) and length (<var>lattr</var>) | :;<var>idattr, pattr, lattr</var>:the xml attributes used in the segment definition elements to specifiy the segment id (<var>idattr</var>) and its starting position (<var>pattr</var>) and length (<var>lattr</var>) | ||
;Result: | ;Result: | ||
:*success: <code>''bseg eseg lseg''</code> - the return value is the begin (''bseg''), end (''eseg'') and length (''lseg'') of the segment specified by the segment expression. The variable <code>RC</code> is set to 0. | :*success: <code>''bseg eseg lseg''</code> - the return value is the begin (''bseg''), end (''eseg'') and length (''lseg'') of the segment specified by the segment expression. The variable <code>RC</code> is set to 0. If the segment expression specifies a label, the values of ''bseg'' and ''eseg'' are equal and ''lseg'' equals zero. | ||
:*error: the command returns the empty string and the error- or warning-code is stored in variable <code>RC</code> | :*error: the command returns the empty string and the error- or warning-code is stored in variable <code>RC</code> | ||
;Description: | ;Description: | ||
:The segment expression <var>segexpr</var> specifies a position in a signal or | :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" | ::{|class="einrahmen" | ||
!<var>segexpr</var> !! description | !<var>segexpr</var> !! description | ||
Revision as of 09:42, 27 April 2011
- Usage
1. Evaluate the segment expression segexpr, using the sampling rate and the length of the current soundfile (see LOAD SOUNDFILE).
SEGMENT segexpr [/S | /?]- segexpr
- the segment expression to be evaluated
/S,/?- silent error handling; generate warnings rather than errors.
2. Evaluate the segment expression segexpr, using the specified sampling rate and length.
SEGMENT segexpr sr l [/S | /?]- sr
- sampling rate in Hz
- l
- maximum signal duration in samples
3. Evaluate the segment expression segexpr, using the sampling rate and the segment definitions stored in the xml-file item xitem.
SEGMENT segexpr xmlfile srattr segtag idattr pattr lattr [/S | /?]- xmlfile
- a xml-file item containing the metadata; the selected element must contain soundfile metadata and the segment definitions must be stored as child elements
- srattr
- the xml attribute of the selected element containing the sampling rate (in Hz)
- segtag
- the xml element tag used for segment definitions
- idattr, pattr, lattr
- the xml attributes used in the segment definition elements to specifiy the segment id (idattr) and its starting position (pattr) and length (lattr)
- Result
-
- success:
bseg eseg lseg- the return value is the begin (bseg), end (eseg) and length (lseg) of the segment specified by the segment expression. The variableRCis set to 0. If the segment expression specifies a label, the values of bseg and eseg are equal and lseg equals zero. - error: the command returns the empty string and the error- or warning-code is stored in variable
RC
- success:
- Description
- 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: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
Segment Expressions
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) |
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!
- See also
