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Implementing Echo Cancel on a Conference Leg
Introduction
The following procedure details the steps for attaching an Echo Canceller to a conference leg, and then recording the output.
Prerequisites
You must have a DSP chip configured with the Echo Cancel function. See Connecting to an ASR (Automatic Speech Recognition) Server.
Guidelines
The Echo Canceller must be attached to the channel before you connect it to the conference or to another DSP receiver.
Procedure
1. Park the channel using the Park Channel 0x00BF message.
2. Create the conference using the Resource Create 0x0124 message.
3. Attach Echo Canceller to channel using the Resource Connect 0x0127 message.
AIBs
Resource A: Channel (Input to Echo Canceller)
Resource B: Slot (of card where conference resides)
Mandatory TLV
0x0602 Resource Type
Resource Type = Echo Cancel (0x0108)
Optional TLVs (to override default card parameters)
0x0673 Echo Cancel Tap Length
0x0674 Echo Cancel NLP Type
0x0675 Echo Cancel ADAPT
0x0676 Echo Cancel Bypass
0x0677 Echo Cancel G.176 Modem Answer Detection
0x0678 Echo Cancel NLP Threshold
0x0679 Echo Cancel CNG Noise Threshold
4. Connect Channel to Conference using Resource Connect 0x0127 message.
5. Attach other DSP Resources as required, such as Record Conference Leg using Record File Start 0x011E message.
6. Disconnect Echo Canceller using the Resource Disconnect 0x0128 message.
AIBs
Source Channel: Span/Channel
Mandatory TLV
0x0602 Resource Type
Resource Type = Echo Cancel (0x0108)
Optional TLVs
None
Example Call Trace
Park Channel span/channel 20/00
H->X
[00 12 00 bf 00 09 ff 00 02 0d 03 00 20 00 0d 03 00 20
00 00]
X->H
[00 07 00 bf 00 09 ff 00 10]
Resource Create - Conference
H->X
[00 20 01 24 00 0c ff 00 01 22 03 00 ff ff 00 03 06 02
00 02 01 00 06 03 00 02 00 00 06 13 00 02 00 06]
X->H
[00 1e 01 24 00 0c ff 00 10 00 01 22 03 04 06 02 00 02 06 10
00 04 00 00 fd fe 06 02 00 02 01 00]
Resource Connect 20/00- Echo Canceller, use slot 4
H->X
[00 17 01 27 00 00 ff 00 02 0d 03 00 20 00 01 01 04 00
01 06 02 00 02 01 08]
X->H
[00 19 01 27 00 00 ff 00 10 00 02 0d 03 00 20 00 01 01 04 00
01 06 02 00 02 01 08]
Resource Connect 20/00- Connect Leg to Conference
H->X
[00 1e 01 27 00 0e ff 00 02 0d 03 00 20 00 55 02 fd fe
00 02 06 02 00 02 01 00 06 12 00 02 00 00]
X->H
[00 1a 01 27 00 0e ff 00 10 00 02 0d 03 00 20 00 55 02 fd fe
00 01 06 02 00 02 01 00]
Record File Start 20/00
H->X
[00 46 01 1e 00 12 ff 00 02 0d 03 00 20 00 01 01 ff 00
06 05 e0 00 04 00 dc 5b 17 05 e1 00 02 00 01 05 e2 00
13 00 01 00 02 2f 50 61 74 45 63 68 6f 2f 6d 79 2e 72
61 77 05 e9 00 02 02 26 05 fb 00 01 ca 05 e6 00 01 0c]
X->H
[00 11 01 1e 00 12 ff 00 10 00 02 0d 03 00 20 00 01 01 04]