How to Generate a Wav File from RTP Flow

This page describes the way to generate a wav file from the RTP flow recorded over an Ethernet interface. The requirement is done by using the Analog properties in the Clarinet filter used online (filter name defined in the profile) or offline (Filter-Run Protocol).

Setting the test conditions

The Clarinet Book USB unit connections and the test condition settings for basic VOIP communication are detailed in the following pages:-

Setting the test conditions for VOIP / Analog filter

The protocol filter file, Lan_auto_rtp_analog.acf (created from a template, by the wizard) specifies the protocols present in the stack.

As the IP protocols are automatically detected by the protocol value, the stack defined in the Protocol specification has the layers D3 to D7 set to Automatic. The RTP protocol is decoded at the level 5, the analog protocol is added to the level 6.

The Analog Measurement tab of the filter includes specifications for both functions: wav file generation and QoS measurement. The filter file Lan_auto_rtp_analog.acf  is configured only to generate the wav files.

  • Modifications that must be made to the recieved voice section:-
    • The codec specifications must correspond to the value set in the PT of the RTP messages.
      For information:-
      • PT=000 è G711 mLaw
      • PT=008 è G711 ALaw
      • PT=018 è G729
    • The output file must specify:-
      • The file name (default= Rtp_analog.wav)
      • The encoding specifications of the file.wav
  • The quality measurement should be set to off if the purpose is only to generate the wav files.

Generating the Wav file

The wav files are automatically created in the working directory: with the basename defined in the filter file (e.g. Rtp_analog_xx.wav). Source and destination IP addresses are added to the basename.

Applying the filter conditions

The processing of the events can be done:-

  • Offline, by using Filter=>Run Protocol:-
    • Source file containing the RTP flow (e.g. Lan_mon.ace).
    • Filter name (e.g. Lan_auto_rtp_analog.acf)
    • Result file generated (e.g. Lan_mon_rlt.ace).
  • Online, at the end of the profile execution, with the following settings:-
    • Configuration file set as WI_ANALOG by Clarinet-Init
      • .
    • Filter name defined in the profile to be executed.
 
Related topic:
Generation of Analog events
Analog filter specifications
 

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