Copyright: Version 1.10, Copyright 1998, Northern Telecom (Nortel), Ltd.


Introduction
WaveView

WaveView is a utility which allows the user to view compressed voice files graphically, play back the voice files through a suitable sound board in a PC, and analyze the characteristics of the voice waveforms recorded in the voice file.

It supports the following voice file formats:

•	Sub-band coding (SBC) in 8K byte voice block format (used by MCE)

•	uLaw PCM voice blocks (used by MCE)

•	Sub-band coding in packet format (used by Norstar)

•	Microsoft .WAV files that have been recorded in 16b or 8b PCM

•	raw 16b PCM files (no header information)

WaveView’s built in transcoding ability allows the user to save files in any of the supported formats.  For example, a .WAV file can be stored in either PCM voice block format or SBC voice block format for playback on an NGen system.

The user can perform accurate time, frequency and power measurements on waveforms using WaveView’s Time Display windows, Spectrum Analyzer and Power Meter capabilities.

Applications

•	Call Progress Tone Detection (CPTD) waveform capture and analysis of cadence and frequency content

•	Conversion of SBC and mLaw PCM Voice Blocks to and from .WAV files

•	Power measurement / noise measurement of signals received from telephone lines

•	Analysis of echo signals and signal distortion from signals recorded from telephone lines


Overview of Features

•	Transcoding between .WAV files, SBC compressed voice files and μLaw PCM Voice Blocks

•	Waveform Time Display

•	Time and Frequency Zoom-incapability

•	Spectrum Analyzer

•	automatic power measurementof the waveform in the zoom window

•	Accurate time  and frequency measurement

•	Audio Playback and  Recording from NGen DSPs

•	Waveform Editing functions (Cut, Paste, Crop, etc…)


Opening and Saving Files

Opening a File

To open a file, access the File|Open menu at the top left of the screen.  This brings up the dialog box shown below:

The File Extension filters out the files in the directory based on the selected file mask.

The File Format specifies the nature of the file, so that WaveView can interpret it correctly.  The 4 file formats available in this release of WaveView are listed below:

1. 	WAV files.  Only monophonic PCM wav files are supported.  Sampling rates other than 8 kHz can be used, and both 8 and 16 bit samples are supported.

2. 	16b PCM files.  These files contain ‘raw’ data (i.e. no header or other non-signal data is included in the file).  The waveforms must be recorded at 8kHz.

3. 	Voice block files.  These are the type of files used with MCE, and include voice compressed using Sub-Band Coding as well as uLaw PCM.  Voice Blocks contain a header and trailing information, and are generally around 8kB per block.

4. 	Sub Band Coded packet data.  This file format is very similar to the SBC Voice Block described above, except that the header and trailing information have been removed.  There is no block structure with this data format.

Saving Files

When a file is opened in WaveView, it is converted into 16b PCM format.  When a file is saved in another format (e.g. sub-band coding), the host processor performs all of the required transcoding.

The File Format specifies the nature of the file, so that WaveView can transcode it correctly.  The 5 file formats used for saving files available in this release of WaveView are listed below:

1. 	WAV files.  Only monophonic PCM wav files are supported.  Sampling rates other than 8 kHz can be used, and both 8 and 16 bit samples are supported

2. 	16b PCM files.  These files contain ‘raw’ data (i.e. no header or other non-signal data is included in the file).  The waveforms must be recorded at 8kHz.

3. 	uLaw Voice block files. These are the type of files used with MCE, and include voice compressed using uLaw PCM.  Voice Blocks contain a header and trailing information, and are generally around 8kB per block. Note that uLaw Voice block files must contain a multiple of 128 samples.  If the original waveform does not contain a multiple of 128 samples, WaveView will pad out the end of the waveform with silence in order to meet this requirement.

4. 	SBC Voice block files. These are the type of files used with MCE, and include voice compressed using uLaw PCM.  Voice Blocks contain a header and trailing information, and are generally around 8kB per block.

5. 	SBC packets.  These are primarily used by Norstar, and do not have any block structure around the voice data.

When saving a file, the user can check a check box in the Save Dialog module to automatically reopen the file that was just saved.  This allows the user to check out the impact that the transcoding had on the signal.  If the Re-open Saved File check box is not checked, the waveform display data is not changed when it is saved to disk in another format.

Files compressed as Sub-band coded Voice Blocks can optionally have zeroes added after each block to pad the block out to 8192 bytes.  This is sometimes done to allow rapid indexing of voice blocks (e.g. for MMFS).  To enable this option, check the 8KB block padding check box before clicking the Save button.


Waveform Time Display
Main Waveform Time Display

When a file has been opened, it is displayed in its entirety in the Main Time Display window along the bottom of WaveView.  A time scale runs underneath the waveform, and a logarithmic power scale (in decibels) runs up the right side of the display.  There are 3 horizontal lines running through this display.  The middle line is the 0 amplitude line, which corresponds to a power of minus infinity.  A perfectly quiet signal with no DC offset would lie along this line.  The blue lines above and below this line are drawn at half of the maximum amplitude of the signal.  The time waveform automatically adjusts its scale so that as much low amplitude detail can be shown as possible.  The amplitude in decibels of the +/- maximum amplitude and +/- half maximum amplitude points are labelled in the right hand axis.

Time and Amplitude

The location of the mouse is tracked while it is within the Main Waveform Time Display, and the corresponding time within the waveform and the amplitude of the signal at that time are displayed in the bottom right corner of WaveView.  A vertical green line indicates the position that the Time and Level display refer to.

Zooming In

In the picture shown at above, a white box is displayed with the waveform inside of the box colored red.  The waveform within the white box is magnified and displayed in the top half of the WaveView display, in the Zoom Time Display Window.To specify the portion of the waveform that is zoomed-in on, click the left mouse button at the start (or end) of the desired waveform portion and drag the mouse button either right or left until the white box surrounds the desired waveform portion.  When you release the left mouse button, the Zoom Time Display Window will be updated to show the selected waveform portion.   The starting time and the duration of the selected waveform portion is displayed in the ‘Select Region’ edit box near the bottom of the WaveView display area.

An alternative way of specifying how many samples are to be selected in the Zoom Time Display Window is to type the duration directly into the Select Region edit box.  This value can be locked in place by checking the Lock checkbox to the right of the edit box.  When locked, the user can drag the mouse across the waveform and the selected region will maintain its width and follow the mouse.  This is useful for analyzing the on/off cadences of call progress tones, for example.  The two buttons to the left of the Select Region edit box allow the selected region to be panned left or panned right without using the mouse.  This allows the user to scroll across the waveform, and examine the waveform as it evolves.

Finer zoom-in control is available within the Zoom Time Display Window itself, and is discussed in the next section.


Zoom Time Display
Zoom Time Display Window

The upper portion of WaveView is a paged control with two pages: Time and Frequency.  Both of these pages display information about the samples selected in the Select Region of the Main Time Display Window at the bottom of the WaveView display.

The Time page contains the Zoom Time Display Window.  This provides a magnified view of the samples selected in the Main Time Display Window Select Region, and allows the user to ‘fine tune’ the select region.  This is done by selecting samples in the Zoom Window itself that the user wishes to zoom further into, and then clicking the right mouse button.  This causes a pop-up menu to be displayed which contains a Zoom In menu item.

Clicking on this menu item will redefine the Select Region of the Main Time Display Window to correspond to the samples selected in the Zoom Time Display window, and redraw the zoom window to fully display these samples.   To zoom back out to the original Select Region setting, right click the mouse button again and select the Zoom Out menu item of the PopUp menu.

The Zoom Time Display Window automatically adjusts its gain independently of the Main Time Display Window, allowing the display to zoom in in both time and amplitude.


View Menu Controls

The following controls are available via the View menu, and via the toolbar at the bottom of the screen:

Go To Start (F5) : Positions the selected region at the start of the waveform

Pan Left (F6): Shifts the selected region to the left by the number of samples in the selected region

Pan Right (F7) : Shifts the selected region to the right by the number of samples in the selected region

Go To End (F8) : Positions the selected region at the end of the waveform

Zoom In (F9) : decreases the number of samples in the selected region by ½, causing the Zoom Window to magnify its time scale by a factor of 2

Zoom Out (F10) : doubles the number of samples in the selected region, causing the Zoom Window to reduce the magnification of its time scale by a factor of 2


Spectrum Analyzer

The upper portion of WaveView is a paged control with two pages: Time and Frequency.  Both of these pages display information about the samples selected in the Select Region of the Main Time Display Window at the bottom of the WaveView display.

The Frequency page contains the Spectrum Analyzer Window.  This provides a frequency spectrum view of the samples selected in the Main Time Display Window Select Region.  The user can zoom in on a particular region of the spectrum for a more detailed view by clicking the left mouse button and dragging it diagonally, so that a white box is drawn around the frequencies and amplitudes of interest.

When the mouse button is released, the spectrum analyzer will re-analyze the waveform samples and update the frequency spectrum view so that the selected frequencies and amplitudes take up the entire spectrum analyzer window.   These settings remain in effect even if the Main Time Display Window Select Region is altered, allowing the user to analyze frequency regions of interest over the entire waveform.  To return to the full frequency spectrum view, right click the mouse button and select Zoom Out on the resulting PopUp menu.


Time and Frequency Measurement

When the mouse is moved in either the Zoom Time Display or the Spectrum Analyzer Display, the position of the mouse in time / frequency is displayed in the panel at the bottom of WaveView, along with the amplitude of the signal at this point.  As well, a small green cross is displayed at the point in the waveform / spectrum that corresponds to the mouse position, allowing the user to precisely position the mouse to read the time/frequency position and amplitude of points of interest in the waveform.  For example, the peak in the Spectrum display indicates a strongly predominant frequency in the spectrum (e.g. part of a DTMF tone pair).  The user can determine the precise frequency by zooming in on the peak of the spectrum, and positioning the green cross on the zoomed-in spectrum display so that it is at the peak of the spectrum.  The frequency and amplitude of this point is displayed in the bottom panel.

As well as the text indication of the frequency and amplitude, a graphical aid is provided to help read the time / frequency and amplitude scales.  The position of the green cross hair is indicated by a small green line right next to the bottom and right-hand axes.  In the above picture, look for a small vertical line between 780 and 790 on the horizontal (frequency) axis, and between -22 and -24 on the vertical (amplitude) axis.  As the mouse is moved, the green cross and these two small lines will also move, following the horizontal position of the mouse and the vertical offset of the waveform.


 Level Measurement

In addition to the vertical amplitude axis, there are two other level measurement aids provided in WaveView.  The RMS power is displayed in the upper right corner of the Zoom Time Display.  This value is calculated by taking the square root of the mean sum of all of the samples in the Select Region after they had been squared (multiplied by themselves).

In addition to the RMS power, two horizontal blue lines are drawn across the time displays, which allow the user to quickly check to see if the waveform is between two thresholds or above or below a specific threshold.  The level in dB that these lines are drawn can be configured by selecting Options | Configure Level Markers and entering the Levels that would be required for full season play.


Audio Playback

In order to play back the waveform, the user’s PC must be equipped with a sound card that can handle an 8kHz sampling rate.  Older sound cards often only provide support for multiples of 11.025 kHz and thus will not be able to provide audio playback.

For PCs that are properly equipped, the user can control playback using the three buttons at the bottom left of the WaveView display.

  F2    Clicking the play button causes the waveform to start playing.

 F3    Clicking the stop button stops playback of the waveform

 F4     Clicking the pause button pauses playback.  To resume playback, click the pause button a second time.

 F12   Clicking the record button opens a dialog box which allows the user to automatically capture a waveform from an NGen DSP on the system.  Click here for more information.

When the waveform is being played, the cursors for both the Main Time Display Window and the Zoom Time Display Window are set to a vertical green bar, which indicates the current location of the audio being played out.  The time / amplitude text in the bottom right corner of WaveView corresponds to the position of the green bar as it advances from left to right across the waveform.  As the audio playback goes through the Select Region, the green bar will appear in the Zoom Time Display Window as well as the Main Time Display Window.

The default playback behaviour is to play the entire waveform.  The user can configure WaveView to play back only the portion of the waveform that is in the Select Region by checking the Play Selected Regions Only check box above the play button.  When this is checked, only the samples in the Select Region will be played.


Recording From a DSP

  F12

To capture a waveform, click the Record button or hit F12.  This pops up the dialog box shown below:

If no DSP could be detected on the system, you will be prompted to check that the C52 and NTBUS device drivers are running.  This can be done using the Drivers applet in the Control Panel.

The main reason to record a waveform from an NGen DSP is to analyze Call Progress Tone  (CPT) signals that have been received by an NGen system but were not recognized by the DSP-based CPT Detector (CPTD).  To capture the signals received by the DSP while the CPTD DSP program is running, select the DSP that you wish to record the signal from (choose ANY if you do not care which DSP is used).  Click the button labeled ‘Start CPTD Auto Capture’.  This causes WaveView to wait for the specified DSP to run the Outdial CPTD application.  To get this to run, get the NGen system to originate a telephone call (e.g. for remote notification of a message in a suitably configured MCE mailbox.)  Once the DSP Outdial application starts to run, WaveView will start capturing the signals received by the DSP and will update the Recording Status to show how many seconds of the waveform have been captured.  You can stop recording either by clicking the ‘Stop CPTD Auto Capture’ button, clicking the Exit button, or waiting for the DSP to stop running the Outdial application.  A recording limit of 5 MB (approximately 10 minutes) has been put in place to avoid using up too much disk space inadvertently.

When a DSP has been selected, or when ANY DSP has been specified and an Outdial DSP application has been detected, the DSP Status display will be shown.  This display shows the functions that are running on the DSP and the percentage of allocated DSP CPU that the function is using.  This may be useful for determining the activity on the system and determining which DSP’s are busy in the system.

Once a waveform has been captured, click the Exit button to return to the main WaveView display.  The captured waveform will be shown on the WaveView time display.  This can be saved using File / Save As.


Editing Functions

WaveView provides the following editing functions via the Edit Menu.  The shortcut keys are shown in brackets.:

Undo (Ctrl+Z): Undoes the last editing function that was performed.

Cut (Ctrl+X): Same as Copy, except it removes the copied samples from the waveform

Copy (Ctrl+C): Copies the samples in the selected region in the main time display window into a local copy buffer

Paste (Ctrl+V): Inserts the samples in the copy buffer before the cursor position in the main time display window

Select All (Ctrl+A): sets the main time display window’s selected region to select all of the waveform

Crop (Ctrl+K): Removes the samples before and after the selected region of the waveform.

Delete(Del): Deletes the samples in the selected region in the main time display window

Insert Silence (Ins): Inserts zero valued samples into the waveform before the cursor position in the main time display window.  The number of samples inserted is equal to the duration of the select region in the main time display window.

Gain (Ctrl+G) : Amplifies the samples in the selected region by the number of decibels specified by the user