[Speex-dev] SDP parameters for DTX and VBR modes

Alexander Chemeris Alexander.Chemeris at sipez.com
Tue Feb 19 15:05:33 PST 2008


Two questions about SDP usage with Speex:

1) How to anounce thet DTX is enabled?

2) What is default value of 'cng'  option? In latest draft it is
defined as following:

      cng: comfort noise generation - either 'on' or 'off'.  If off then
      silence frames will be silent; if 'on' then those frames will be
      filled with comfort noise.

3) What is the relation between 'vbr' and 'cng' options?
Is there unacceptable combinations of them?
In lastest draft 'vbr' is defined as following:

      vbr: variable bit rate - either 'on' 'off' or 'vad' (defaults to
      off).  If on, variable bit rate is enabled.  If off, disabled.  If
      set to 'vad' then constant bit rate is used but silence will be
      encoded with special short frames to indicate a lack of voice for
      that period.

Alexander Chemeris.

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