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The Digital Signal Processor (DSP) Resource Calculator is  a web-based tool that helps calculate the number of DSPs required on  the system. It also determines the number of calls that can be handled  simultaneously, taking into consideration each of the Coder-Decoder  (codec) standards. This tool requires information such as the platform  type, Cisco IOS  release number and Interface modules to calculate the DSPs. This document provides information on how to calculate DSPs for TDM Voice service and Video conferencing service.


Why do you need DSP?



No. of DSPs required = Voice Termination + Audio IP Services + Video IP services



1. Voice Termination


  • TDM Trunk Termination
  • DSP Sharing
  • H.320 TDM Video
  • Audio Security


2. Audio IP Services


  • Audio Conferencing
  • Audio Transcoding
  • Audio Security
  • DTMF interworking
  • Acoustic shock prevention
  • Media Forking


3. Video IP Services


  • Video conferencing
  • Video Transcoding



DSP Media Resources


  • Audio Conferencing:    Mixing RTP streams for multi-party conference bridges


  • Audio Transcoding and Transrating:     Support multiple codecs  on the same call  (e.g., G.711-G.729A)


  • Video Conferencing:    Mixing video streams for multi-party conferences


  • Cisco Unified Border Element:   Media Enhancement, Acoustic Shock Prevention, Noise Reduction, Video Quality Metrics, Transcoding and Transrating


  • Voice Termination:    Terminating TDM trunks and encoding, compressing and packetizing the voice.


Codecs and Transcoding Type

Codecs and Transcoding Type




  1. Low complexity: G.711, clear-channel, fax/modem passthrough
  2. Medium complexity: G.729A/G.729AB, G.722, G3 fax relay
  3. High complexity: G.729/G.729B, iLBC, SG3 fax relay, modem relay
  4. Very High complexity: ISAC

Transcoding type

  1. Traditional: G.711-any
  2. Universal: Any-to-any
  3. Secure transcoding (CME only)



Transcoding and Transrating



What is Transcoding?


Support multiple codecs on the same call.

  • Types

          G.711-any transcoding

          Any-any transcoding (universal),

          e.g. iLBC to G.722

  • H.323 and SIP
  • Universal transcoding support

         CUBE as of 12.4.20T

         CUCM as of 7.1.5


What is Transrating?


  • Different packetizations of the same codec. E.g. G.729A 20ms to G.729A 30 ms
  • SIP-SIP Support only
  • CUBE support as of 15.0.1M


How to Calculate DSPs?


DSP Calculation Tool supports, ISR G1/G2:  2800/3800, 2900/3900, PVDM2 & PVDM3


1. DSP Requirement for TDM Gateway Service & Call volume calculation



Click --> Next



Click  --> Next





2. DSP Requirement for Video Conference Service





Click  --> Next


Click  --> Next


Click  --> Next


Understanding the output of  "show voice dsp group all"


Related Information


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