DSP question - How many for ..

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Oct 27th, 2008
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I`m trying to understand DSP and how many for required. Attached is a screen shot form the DSP Calculator for a single port 1 card with 30 channels. Show that I require 1 x PVDM2-32 or 2 x PVDM2-16 for optimized result, what is the relationship between the number of channels, D channel and the number of DSP/ PVDM


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tim.giles Mon, 10/27/2008 - 03:38
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Basically the PVDM2 allows for increased transcoding and conferencing and uses a different DSP to the PVDM (C5510 DSP's).

Five PVDM2 models exist:


PVDM2-16 (1 DSP)

PVDM2-32 (2 DSP's)

PVDM2-48 (3 DSP's)

PVDM2-64 (4 DSP's)

The XX in the PVDM2 part number indicates the max number of voice channels it can terminate.

i.e. PVDM2-32 = max 32 voice calls for each DSP.

Here's a link for the PVDM2's which explains the max number of channels in G711:


Hope this helps..

Please rate useful posts..

allan.thomas Mon, 10/27/2008 - 05:50
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Further to the good information for Tim, the main aspect to consider is the relationship between DSPs and the complexity chosen.

There are specifically four different types of complexity available for use, and each type governs the numbers of DSPs required.

There is Flex, Medium, High and Secure complexity types, therefore if you require to maximise your call density using G711 only, then you would opt for FLEX (system-default) which will utilise your DSPs according to the number of timeslots configured 1:1 for an E1 for example a single PVDM2-32

However if you are using CFBs and/or XCoders, then this then this will signifcantly changes the number of PVDMs required to provide 30 channels plus x or y number of CFBs/XCoders.

The DSP Calc will help you to determine the number of PVDMs required, and is the necessary codec compexity.



Pls rate helpful posts. Thanks

iptuser55 Thu, 10/30/2008 - 06:07
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Just to follow on from another post as below. If they are not using DSP for anything else then would the DSP below PVDM2-64 be good enough for both E1`s. Is there a commend to check if you have spare DSP`s



I have to configure a router 3845 with one NM-HDV2-2T1/E1 and two PVDM2-64. I have typed the following commands:

(router-config)# card type e1 1 1

(router-config)# controller e1 1/0

(config-controller)# pri-group timeslots 1-31

And the router shows the following message in console:

% Not enough DSP resources available to configure pri-group on controller E1 1/0

% The remaining dsp resources are enough for 0 time slots.

% For current codec complexity, 2 extra dsp(s) are required to create this voice port.

Does anyone know what can I do? The only solution is to add more DSPs?


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