Overview
GLC View is a waveform-viewing application. It has been designed specifically as a companion component for the GL
Communications Inc. T1/E1 Echo Canceller Test Suite. The program may be used to view previously captured raw data files and
their corresponding power.
Features
- Document/View Architecture.
GLCView separates the data being viewed from its graphical presentation.
- Multiple Document Interface.
The number of waveforms that can be simultaneously viewed is limited only by the
resolution of the viewing screen.
- Synchronized raw data and windowed power graphs
The power graph is automatically synchronized with the
raw data graph. Thus when the raw data graph is scrolled, the power graph scrolls with it.
- Zoom-in and zoom-out capability
The power graph is equipped with zoom-in zoom-out capability. Users may
select a portion of the power graph with the mouse and zoom the selected portion to the entire graph area, thus allowing arbitrarily
precise viewing.
- User-selectable power window length.
The window in which the power is calculated is selectable by the user
from 1 to 1000 ms.
Description
GLCView is a "Multiple Document Interface" (MDI) application. Its main window consists of an MDI frame, including a menu, toolbar,
and standard system controls to maximize, minimize, resize, move, and close the window. It also contains the viewing area, in which
the an indefinite number of files may be graphically displayed.
The display area of the view is divided into two panes. The upper pane is used to graphically display the raw data read from the file,
which GLCView converts from compressed to linear form if necessary. For this reason, the top pane is referred to as the linear pane.
GLCView uses the lower pane to display the power graph corresponding to the linear data in the upper pane, and is therefore referred to
as the power pane.
Linear Pane: The linear pane is used to graphically display linear data in fivesecond segments. The pane contains a plot area
in which the graph is displayed, horizontal(time) and vertical (linear value) axes, and controls that allow you to scroll through the data,
and to size the graph to the plot area. When the graph is first displayed, GLCView analyzes the data in the first five seconds and uses the
maximum and minimum values to scale the data to the plot area. While scrolling through the file, the character of the data may change in
such a way that the initial scale is no longer appropriate. Linear pane's Zoom Out button helps to rescale.
Power Pane: The power pane is used to graphically display the power corresponding to the linear data in the upper pane.
GLCView computes the power data by passing a sliding window over the linear data and computing the average power in that window.
The pane contains a plot area in which the graph is displayed, horizontal(time) and vertical (linear value) axes, a scroll bar that allow you
to scroll through the data, and buttons that allow you to zoom out and to bring up the Power Window dialog.
Data Format: In this dialog, the file format is selected. The user may select E1/A-Law format for E1 systems, or T1/m-Law
for T1 systems. The user may also select 16-bit Intel ("Little-Endian" files or 16-bit Motorola ("Big-Endian") PCM files.
Power Calculation Window Dialog: GLCView computes the graph for the power pane in a variety of ways, as per
the various tests in ITU-T G.168.
The various options are:
- G.168 Rectangular Window
The power will be calculated by passing a sliding window over the linear
data and computing the average power in that window. The sliding window is moved one point at a time over the linear data, so that
each point in the linear data has a corresponding point in the power graph. The average power computed in the sliding window is
assigned to the last point in the window.
The window length can be set to any value from 1 millisecond up to 5 seconds. The
value must be an integer. The default is 35 ms.
In conjunction with the power window, you may also provide the ITU-T G.168
Voice band Filter, which attenuates signal power outside the normal voice band of approximately 200 - 3500 Hz.
- G.168 Level Measurement Device
This device is essentially a frequency-weighed signal that has been
squared to produce the power, and then passed through a 35 ms exponential filter. This device is specified for a number of tests,
including Test 2, which deals with the convergence characteristics of the echo canceller.
- G.168 CSS Single-Talk
This setting should be used to measure the average power of CSS single-talk
files. The average power over a full cycle of CSS single-talk signal is calculated. The Active Portion Only check box is provided to
calculate the power over the active portions of the signal.
- G.168 CSS Double-Talk
This setting is used to measure the average power of CSS double-talk files.
The average power over a full cycle of CSS double-talk signal is calculated. The Active Portion Only check box is provided to calculate
the power over the active portions of the signal.
Vertical Scale Dialog
The Vertical Scale dialog is available for Linear PCM formats only. This button is
not visible if encoded data format is chosen for viewing, as ITU-T G.168 has specific recommendations for computing the power of
these signals.
The following options are available:
- dB Relative to Full-Scale Sine Wave
The point-by-point RMS power of the signal is
calculated according to the method specified in the Power Calculation Dialog. The power is expressed relative to the power of a
full-scale sine wave. The full-scale range is -32768 counts to 32767 counts.
- dB Relative to Full-Scale Square Wave
The point-by-point RMS power of the signal is
calculated according to the method specified in the Power Calculation Dialog. The power is expressed relative to the power of a
full-scale square wave. The full-scale range is -32768 counts to 32767 counts. The values calculated by this method are 3.01 dB
lower than those stated relative to a full-scale sine wave.
- A-Law Equivalent dBm
This option is normally used for linear files that were originally
derived from, or must be compared to, A-Law compressed files. The ITU-T G.168 A-Law formula is used to calculate the power.
However, A-Law is a 13-bit format, whereas Linear PCM is a 16-bit format. Bit Depth specifies whether all 16 bits are being used,
or whether 13-bit quantities are packaged in 16-bit numbers.
If bit depth specifies 13, it notifies the viewer that the signal is
a 13-bit quantity. In other words, the signal values are exactly 13-bit A-Law expanded values packaged in a 16-bit format. The
viewer can use the ITU-T G.168 A-Law power calculation formula directly for such signals.
If bit depth specifies 16, it notifies
the viewer that the signal is a 16-bit quantity. The viewer must therefore downshift the sample values by 3 bits to use the
ITU-T G.168 A-Law power calculation formula.
- µ-Law Equivalent dBm
This option is normally used for linear files that were originally
derived from, or must be compared to, µ-Law compressed files. The ITU-T G.168 µ-Law formula is used to calculate the power.
However, µ-Law is a 14-bit format, whereas Linear PCM is a 16-bit format. Bit Depth specifies whether all 16 bits are being used,
or whether 14-bit quantities are packaged in 16-bit numbers.
If bit depth specifies 14, it notifies the viewer that the signal is
a 14-bit quantity. In other words, the signal values are exactly 14-bit µ-Law expanded values packaged in a 16-bit format. The
viewer can use the ITU-T G.168 µ-Law power calculation formula directly for such signals.
If bit depth specifies 16, it notifies
the viewer that the signal is a 16-bit quantity. The viewer must therefore downshift the sample values by 2 bits to use the
ITU-T G.168 µ-Law power calculation formula.
Buyer's Guide
Please Note: The XX in the Item No. refers to the hardware platform, listed at the
bottom of the Buyer's Guide, which the software will be running on. Therefore, XX can either be DPT,
DPE, PCT, PCE, HDT, HDE, DLT, DLE or UTE depending upon the hardware.
