Difference between revisions of "Programmer Guide/Command Reference/SEGMENT"

From STX Wiki
Jump to navigation Jump to search
(Examples)
(Examples)
Line 76: Line 76:
 
  segment 1s_+100 10000 5*10000 // addresses 1 second to 1 second plus 100 samples
 
  segment 1s_+100 10000 5*10000 // addresses 1 second to 1 second plus 100 samples
  
  segment seg1 ''xmlfile''  
+
  segment seg1 ''xmlfile'' SR ASeg ID P L  // addresses the whole signal of segment '''seg1'''
  segment seg1:b_
+
  segment seg1:b_seg2:e+2s ''xmlfile'' SR ASeg ID P L // addresses the signal from the beginning of '''seg1''
SegmentA:B+100_+10s
+
                                                    // to the end of '''seg1''' plus 2 seconds
</pre>
 
addresses 100 samples after the beginning of SegmentB for a duration of 10 seconds
 
 
 
<pre>
 
SegmentB
 
</pre>
 
addresses SegmentB
 
 
 
<pre>
 
SegmentA:B_SegmentB:E
 
</pre>
 
addresses the beginning of SegmentA to the end of SegmentB
 
 
 
<pre>
 
SegmentB:E_<nowiki>-</nowiki>100ms
 
</pre>
 
addresses 100 milliseconds before the end of SegmentB to the end of SegmentB
 
 
 
Notes: For some expressions, the values <code>number%</code> (percentage of the full duration) and <code>number%%</code> (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 <code>segmentname</code> 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:
 

Revision as of 11:52, 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 variable RC is set to 0.
Note: If the segment expression specifies a label, the return value is pos pos 0.
  • error: the command returns the empty string and the error- or warning-code is stored in variable RC

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
bexpr a position (label) at bexpr
bexpr_eexpr a segment with begin bexpr and end expr
bexpr_+lexpr a segment with begin bexpr and length lexpr (end = bexpr+lexpr)
eexpr_-lexpr 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).

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/or length the segment with id segid
segid:b begin of the segment with id segid (see examples) 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

See also

class BDataSet, LOAD SOUNDFILES, INT, NUM, file item (xml)

Examples

segment 0_4s       // addresses 0 samples to 4 seconds of the current soundfile
segment 50%-1s_+2s // addresses 2 seconds in the middle of the current soundfile
segment 1s_+100 10000 5*10000 // addresses 1 second to 1 second plus 100 samples
segment seg1 xmlfile SR ASeg ID P L  // addresses the whole signal of segment seg1
segment seg1:b_seg2:e+2s xmlfile SR ASeg ID P L // addresses the signal from the beginning of 'seg1
                                                    // to the end of seg1 plus 2 seconds