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

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==Usage==
 
==Usage==
 
'''1.''' Evaluate the segment expression <var>segexpr</var>, using the sampling rate and the length of the [[Programmer_Guide/Concepts/Current_Soundfile|current soundfile]] (see [[../LOAD|LOAD SOUNDFILE]]).
 
'''1.''' Evaluate the segment expression <var>segexpr</var>, using the sampling rate and the length of the [[Programmer_Guide/Concepts/Current_Soundfile|current soundfile]] (see [[../LOAD|LOAD SOUNDFILE]]).
:<code>SEGMENT <var>segexpr</var> [ [[Programmer_Guide/Command_Reference_Options/Silent|/Silent | /?]] ]</code>
+
 
 +
SEGMENT <var>segexpr</var> [ [[Programmer_Guide/Command_Reference_Options/Silent|/Silent | /?]] ]
 
:;<var>segexpr</var>:the segment expression to be evaluated
 
:;<var>segexpr</var>:the segment expression to be evaluated
 
:;<code>/S</code>, <code>/?</code>:silent error handling; generate warnings rather than errors.
 
:;<code>/S</code>, <code>/?</code>:silent error handling; generate warnings rather than errors.
 +
 
'''2.''' Evaluate the segment expression <var>segexpr</var>, using the specified sampling rate and length.
 
'''2.''' Evaluate the segment expression <var>segexpr</var>, using the specified sampling rate and length.
:<code>SEGMENT <var>segexpr sr l</var> [ [[Programmer_Guide/Command_Reference_Options/Silent|/Silent | /?]] ]</code>
+
 
 +
SEGMENT <var>segexpr sr l</var> [ [[Programmer_Guide/Command_Reference_Options/Silent|/Silent | /?]] ]
 
:;<var>sr</var>:sampling rate in Hz
 
:;<var>sr</var>:sampling rate in Hz
 
:;<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> [ [[Programmer_Guide/Command_Reference_Options/Silent|/Silent | /?]] ]</code>
+
 
 +
SEGMENT <var>segexpr xmlfile srattr segtag idattr pattr lattr</var> [ [[Programmer_Guide/Command_Reference_Options/Silent|/Silent | /?]] ]
 
:;<var>xmlfile</var>:an [[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>:an [[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)

Revision as of 19:19, 28 April 2014

Usage

1. Evaluate the segment expression segexpr, using the sampling rate and the length of the current soundfile (see LOAD SOUNDFILE).

SEGMENT segexpr [ /Silent | /? ]
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 [ /Silent | /? ]
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 [ /Silent | /? ]
xmlfile
an 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 at position lpos, the return value is lpos lpos 0.
  • error: the command returns an empty string. As usual, the error, or warning code (0 on success) is stored in the variable RC.

See also

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

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 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

Address 0 samples to 4 seconds of the current soundfile:

segment 0_4s       

Address 2 seconds in the middle of the current soundfile:

segment 50%-1s_+2s

Address 1 second to 1 second plus 100 samples of a signal with 10kHz sampling rate a 5 seconds duration:

segment 1s_+100 10000 5*10000 

Note: XML attributes and element names and segment ids are case sensitive!

Address the whole signal of segment seg1:

segment seg1 xmlfile SR ASeg ID P L  

Address the signal from the beginning of seg1 to the end of seg1 plus 2 seconds:

segment seg1:b_seg2:e+2s xmlfile SR ASeg ID P L