IP Network Series 2 NLP Control Support


The IP Network Series 2 card NLP Control Support feature allows the enabling or disabling of the Non-Linear Processor (NLP) sub-component within the IP Network Series 2 card Echo Cancellation control. This feature is supported by adding new bitmap values to the RTP Echo Cancellation (0x0103) TLV. This TLV remains backward compatible to allow enabling and disabling of the existing echo cancellation function.

This feature is not supported by the VDAC-ONE card.


Currently, the master echo cancellation enable and disable option is the only option available for echo cancellation in the IP Network Series 2 card.

If Echo Cancellation is enabled, the NLP is also enabled.

If Echo Cancellation is disabled, the NLP is also disabled.

The advantage of disabling the NLP while echo cancellation is enabled, is in cases where heavy double-talk scenarios are expected. Double-talk results in clipping (removal) too much voice from the voice path, causing the voice recognition software to fail to detect voice patterns. Disabling the NLP solves this problem.


The NLP enable and disable function is allowed only when echo cancellation is enabled, since NLP cannot be enabled when echo cancellation is disabled.

API Messages Used

Resource Attribute Configure (0x00E3) message

Resource Attribute Query (0x00E4) message

Configuring and Querying

The RTP Echo Cancellation (0x0103) TLV is configured by the Resource Attribute Configure (0x00E3) message.

The RTP Echo Cancellation (0x0103) TLV can be queried by the Resource Attribute Query (0x00E4) message to show the correct value allowed.


The modified RTP Echo Cancellation (0x0103) TLV provides the following bitmap information in the value field:

Bit 0 is the master enable and disable for Echo Cancellation

Bit 1 enables and disables NLP

NLP is enabled if Bit 1 is set to 0 (for backward compatibility), and disabled when Bit 1 is set to 1

Bits 2-7 are reserved and set to 0 in all configuration attempts.

Refer to the TLV chapter in the API Reference.