VAD / CNG / DTX

VAD (Voice Activity Detection) / DTX (Discontinuous Transmission) / CNG (Comfort Noise Generator) are used to reduce the transmission rate during inactive speech periods while maintaining an acceptable level of output quality. VAD classifies the input signal into active speech, inactive speech or background noise. Based on the VAD decisions, DTX inserts Silence Insertion Descriptor (SID) frames during the silence intervals. During silence, SID's are periodically sent to the CNG module, which generates ambient noise during periods of inactive speech on the receive side.

Technical Specification

• Robust algorithm , works under a variety of background noise conditions.
• Uses an adaptive smoothing algorithm to avoid clipping of speech at active to inactive speech transition regions.
• Efficient Noise Generation
• Support for discontinuous transmission (DTX) of inactive frames (based on changes in inactive speech signal)
• Speech detection at low signal-to-noise ratios
• Adapts to changing background noise
• Reentrant, multi-channel implementation
• Configurable frame size
• C callable APIs

Applications

• Voice Over Packet Systems
• Digital Telephone Answering Machines
• Speech Enhancers

Platforms

• Currently supported on TI C64x™ (TMS320C64xx™) and TI C64x+™/DaVinci™ (DM644x™)
• For further details contact mkt@ittiam.com