Programmer Guide/Command Reference/SEGMENT

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.
• 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 position in a signal or the begin and end of a part of a signal.

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: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