Programmer Guide/Command Reference/SEGMENT: Difference between revisions
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:;<var>l</var>:maximum signal duration in samples | :;<var>l</var>:maximum signal duration in samples | ||
'''3.''' Evaluate the segment expression <var>segexpr</var>, using the sampling rate and the segment definitions stored in the [[Programmer_Guide/Shell_Items/File|xml-file item]] <var>xitem</var>. | '''3.''' Evaluate the segment expression <var>segexpr</var>, using the sampling rate and the segment definitions stored in the [[Programmer_Guide/Shell_Items/File|xml-file item]] <var>xitem</var>. | ||
:<code>SEGMENT <var>segexpr xmlfile srattr segtag idattr pattr lattr</var></code> | :<code>SEGMENT <var>segexpr xmlfile srattr segtag idattr pattr lattr</var> [/S | /?]</code> | ||
:;<var>xmlfile</var>:a [[Programmer_Guide/Shell_Items/File|xml-file item]] containing the metadata; the selected element must contain soundfile metadata and the segment definitions must be stored as child elements | :;<var>xmlfile</var>:a [[Programmer_Guide/Shell_Items/File|xml-file item]] containing the metadata; the selected element must contain soundfile metadata and the segment definitions must be stored as child elements | ||
:;<var>srattr</var>:the xml attribute of the selected element containing the sampling rate (in Hz) | :;<var>srattr</var>:the xml attribute of the selected element containing the sampling rate (in Hz) | ||
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;Description: | ;Description: | ||
:The segment expression <var>segexpr</var> specifies a position in a signal or the begin and end of a part of a signal. | :The segment expression <var>segexpr</var> specifies a position in a signal or the begin and end of a part of a signal. | ||
::{class="einrahmen" | ::{|class="einrahmen" | ||
!<var>segexpr</var> !! description | !<var>segexpr</var> !! description | ||
|<code>''bexpr''</code> || a position (label) at ''bexpr'' | |<code>''bexpr''</code> || a position (label) at ''bexpr'' | ||
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|} | |} | ||
: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). | :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" | ::{|class="einrahmen" | ||
!value !!description !!comment | !value !!description !!comment | ||
|<var>x</var> || <var>x</var> samples | |<var>x</var> || <var>x</var> samples | ||
Revision as of 09:05, 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. - 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 position in a signal or the begin and end of a part of a signal.
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 comment x x samples xms x milliseconds xs x seconds xHz periode duration of a harmonic tone with x Hz
=sampling-rate / xxkHz periode duration of a harmonic tone with x Hz
=sampling-rate / (x * 1000)
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
