Chapter 4
MDL’s Speaker Phone
Overview
The Speaker Phone is a robust audio communications Plugin that provides users with high quality, echo-free sound within a straightforward, user-friendly interface. The Speaker Phone also incorporates powerful audio compression algorithms that preserve high quality sound but use minimal amounts of bandwidth. Additionally, the Speaker Phone utilizes multicast routing in order to further minimize bandwidth usage.
The Speaker Phone and the Audio Tool cannot be run at the same time. You should choose between the two depending on your network configuration and what other people you conference with will be using.
Speaker Phone Requirements
The Speaker Phone Plugin is a powerful, easy-to-use tool that provides conference members with the functional equivalent of a normal speaker phone. The Speaker Phone also includes audio compression algorithms that allow users to experience good audio quality while using a minimal amount of bandwidth.
There are certain system requirements necessary for the proper operation of the Speaker Phone Plugin. The first is that the Speaker Phone Plugin uses multicast routing only. In order to use it, everyone in the conference must have multicast installed on their machine, and they must have the proper multicast route added. Also, all networking equipment that connects the conference members must be able to properly handle multicast packets.
Secondly, the Speaker Phone Plugin is not interoperable with the Audio Tool. This means that everyone in the conference should be running the same audio Plugin.
The Speaker Phone Plugin should work well with most microphones and speakers; however, MDL recommends using either the MDL Call Port or the MDL microphone and external speakers for best performance.
Licensing
The Speaker Phone Plugin uses the same license points as the Audio Tool, which means that you can only have one of the two running at any given time. In order to change which audio Plugin loads when you run Communique!, you should use the Plugin Configuration Tool, which is found on the Conference Manager’s Options menu.
The Speaker Phone Interface
The Speaker Phone Plugin provides users with an interface that is both easy to use and understand, and powerful enough to enable users to set their audio to their tastes.
The Speaker Phone’s interface centers around a level meter that displays the current level of sound being picked up by the microphone. As the audio level being picked up changes, the number of green bars displayed on the level meter fluctuates. As the level reaches the top of the meter, the green bars turn red, indicating that the current level of input could be excessively high.
Also found on the level meter are two red hash marks, alongside the level indicator. These red marks indicate the current level of the "Silence Sensor", which will be discussed later. Beneath the level meter is a field that displays the current status of the audio channel, displaying the word "Talking" when you are transmitting, and "Listen" when another conference member is speaking. When mute is on and you speak, the word "Muted" appears in the status area.
On both sides of the level meter are slider bars that allow the user to control volume. To the left of the meter is the microphone gain control, which sets the speaker phone’s sending volume. To the right of the meter is the volume control for the audio that you receive. Directly above the volume controls are buttons which allow you to control whether you send and receive audio. If the button with the picture of the microphone on it is selected, then you will send audio; if it is deselected, you will not transmit audio to the conference. In the upper right hand corner, the button with the speaker on it mutes and unmutes audio. If the button is selected, then you will receive audio.
Directly above the level meter is a button with a picture of tools on it. Clicking on that button brings up the Tool Box panel for the Speaker Phone.
The menu bar along the top of the Speaker Phone contains the Audio and Help menus. The various menu options allow users to launch the Tool box, which is used to configure the Speaker Phone, Close the Plugin, and to get help text.
Using the Speaker Phone
Like the Audio Tool, the Speaker Phone audio automatically starts when a conference is initiated. Assuming that all of your external audio devices are connected properly, you will be able to speak into the microphone and be heard by other conference members immediately. You will also hear all of the other conference members when they speak.
If all of the other conference members sound too loud or too quiet, you should adjust your audio playback volume to an appropriate level. If , on the other hand, one member sounds too loud (or too quiet) but the others sound fine, you should have him adjust his volume appropriately.
If other conference members request that you adjust your sending volume, you should do so as well. If you have your sending volume seat at 100 and other conference members complain that your audio is too quiet, you may need to speak closer to the microphone. On a self powered microphone, this may indicate that you have a weak battery.
There are several options available to the user for fine tuning the Speaker Phone and maximizing its performance. The setting that is used most is the Silence Sensor, which sets the threshold at which audio is sent.
The Silence Sensor
The Silence Sensor reduces audftslraffic by filtering low level background noise, enabling you to only send audio when you are speaking. The Silence Sensor can be set by clicking on the audio level meter at the point where you wish to set the sensor. The red marks on the meter that indicate the sensor level should move to the spot you select.
Ideally, the Silence Sensor should be set at a point slightly above the level of ambient room noise when you aren’t speaking. To set it properly, set the microphone where it will be when you are using it, and set the Silence Sensor at the top of the green bars on the audio level meter. When you are in a conference, the status field under the meter should only say "Talking" when you are actually speaking.
It is also important not to set the Silence Sensor too high. If you have it set too high, you will not begin to send audio as soon as you start speaking, and other conference members will hear a sort of "clipping" effect.
The Speaker Phone includes a feature that will set the Silence Sensor automatically so as to prevent conference members from inadvertently monopolizing the audio channel by sending constantly. If a user transmits constantly for several seconds at a uniform level, his Silence Sensor is reset to a higher level to prevent them from broadcasting noise to the conference.
This setting can be changed from within the Speaker Phone’s configuration file. See the Communique! Administrator’s Guide for details.
The Speaker Phone Tool Box
The Speaker Phone’s Tool Box provides users with a facility to change various settings on the Speaker Phone. The settings that can be changed include echo suppression and compression, and the input and output devices can be selected.
Echo Suppression
Sometimes if people in the conference have their microphone and speakers near each other, the microphone can pick up sound from the speakers and rebroadcasts it. When this happens, it is referred to as "echo" and it can reduce the quality of sound on the audio channel. The Echo Suppression setting works to eliminate this echo. Set at 10, the Echo Suppression feature eliminates all echo from the conference. Setting it to 0 turns it off. Under normal circumstances, Echo Suppression should be set to 10.
When Echo Suppression is set to a value between 0 and 10, white marks similar to those of the Silence Sensor appear on the Audio Level Meter. They indicate the current Echo Suppression level.
Compression
The Speaker Phone provides users with several powerful compression algorithms, capable of lowering the bandwidth consumed by audio significantly. The three compression settings available to users are 64 kbps, which is normal uncompressed audio, 13.3 kbps, and 6.6 kbps. When a conference member changes his audio compression setting, all other conference members are automatically set to the same value. If compressed audio sounds choppy or distorted on your machine, your workstation may lack the processing power necessary to decompress the audio. You can verify this by trying uncompressed audio, or by stopping video temporarily to see if your audio quality improves.
Input Devices
The Speaker Phone automatically senses the audio input devices available, and displays an icon corresponding to each device. In order to select one of the devices as your audio input device, simply click on its icon. Only one input device can be selected at a time, so when you select an input device, any other input device that you have selected is automatically deselected. Most commonly, the audio devices available will be the microphone and line in.
Output Devices
The audio output devices available to the user are also automatically detected by the Speaker Phone. Corresponding icons are displayed, and you can select the output devices that you wish to activate, or deactivate. Any number of audio output devices can be activated at any time, so clicking on one of the icons toggles its current state without affecting any of the others. Audio output devices that are commonly available include external speakers, headphones, and line out.