User manual POLYCOM EF1210TEC ADDENDUM TO THE EF1210
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Manual abstract: user guide POLYCOM EF1210TECADDENDUM TO THE EF1210
Detailed instructions for use are in the User's Guide.
[. . . ] EF1210TEC ADDENDUM TO THE EF1210 USER MANUAL
Since the EF1210TEC is largely based on the EF1210, most of the information in the EF1210 User Manual applies to the EF1210TEC. This document describes the TEC features, and the difference between the operation and configureation of the EF1210TEC and the standard EF1210.
INTRODUCTION
The EF1210TEC is a unique product that is designed to cancel echoes caused by the transmission network as well as acoustic echoes in the local room. There are a total of eight echo cancellation channels on the EF1210TEC. [. . . ] That is, if the bridge sends the local site's audio back to itself. When the EF1210 is used in this type of application, it will remove its own audio from the incoming signal, while allowing audio from other sites to come through. To generate a mix minus, send the mix of all transmitted audio (including all local microphones) to the TEC Reference input. This will send local audio to the remote sites, and give the TEC a reference. The TEC will cancel any delayed echo from the codec signal and pass it on to the TEC Out. This can be sent to the AEC Reference (this signal now contains audio from the remote sites) and out into the room. The other AEC channels will use this reference to prevent acoustic echo from being sent back out onto the network.
TEC Input AEC Ref TEC Ref Play Amix In
TEC Out To CODEC Room Audio
Video CODEC
Line In Line Out
TEC Input AEC Ref TEC Ref Play
TEC Out To CODEC Room Audio Record To TEC Ref
In 1 In 2
Master Out
Line Mixer
Record Amix In To TEC Ref
EF1210TEC
In 2 In 3 In 4 In 5 In 6 In 7 In 8 Out 2 Out 3 Out 4 Out 5 Out 6 Out 7 Out 8 In 1 In 2 In 3 In 4 In 5 In 6 In 7 In 8 Direct Out 1
EF1210TEC
In 2 In 3 Direct Out 2 In 4 Direct Out 3 In 5 Direct Out 4 In 6 Direct Out 5 In 7 Direct Out 6 In 8 Direct Out 7 In 8 Direct Out 8 Direct Out 8 Out 8 In 7 Direct Out 7 Out 7 In 6 Direct Out 6 Out 6 In 5 Direct Out 5 Line In Line Out Out 5 In 4 Direct Out 4 Out 4 In 3 Direct Out 3 Out 2 Out 3 In 1 In 2 Direct Out 1 Direct Out 2
High Delay Video CODEC
8-channel Automixer
Aux Aux Master Out
8-channel Automixer
Master Out
Low Delay Video CODEC
Line In Line Out
Figure 2a: Mix Minus Configuration
Figure 2b: High/Low Delay Configuration
Using the EF1210TEC in High/Low Delay Applications
In some applications, the signal from another site may arrive from two different paths with different delays. This is not a typical echo problem in which local talkers hear themselves return through the system. Rather, they will hear talkers from another site twice, possibly separated by several hundred milliseconds. This may occur if some sites are communicating with each other over wide bandwidth connections, and also with a larger number of sites on a low bandwidth bridge. The high bandwidth sites may communicate with each other over both the wide bandwidth and narrow bandwidth networks. Figure 2b shows how this type of system may be connected.
ASPI Digital - The Sound of DSP
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Application Note: 121
EF1210TEC Addendum
Systems with More Than Seven Microphones
If more than seven microphones are needed, one or more EF1210s may be added to the system to provide echo cancellation on each microphone channel. In general, only one EF1210TEC is needed in the room, and standard EF1210s may be used for additional microphones.
CONFIGURING THE TEC
The AEC channels of the EF1210TEC can be calibrated and configured as described in the EF1210 User Manual. The EF1210TEC may be configured as a standard EF1210 by setting the DIP switch labelled "Reserved" next to the Device ID 16 DIP switch. [. . . ] This will allow echoes to be found more quickly than if the Transmission Delay Compensator had to search over the entire 2 second range. It is important not to set the range too narrowly, because if the delay falls outside of the search range, the TEC will not be able to cancel echoes. The current settings can be queried with a question mark as the argument.
ASPI Digital - The Sound of DSP
3 [. . . ]
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