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SDP RFC is silent on the sequence of codecs . so my question is can we send FMTP line above RTPMAP?

Nbajam 2015
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1 Answers1

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There is no any standard for this as it is codec dependent. If your software includes also codec's, then you should pass these parameters to your codec interface or configure your codec accordingly. Each codec expects different parameters, so there is no any high-level format that should be respected.The processing differs from codec to codec. Sometime it contains values that can be omitted, sometimes contains important parameters which must be used accordingly.

The format is like this: a=fmtp PAYLOADNUMBER PARAMETERS_SEPARATED_BY_SEMICOLON

For example for G.723 you can have something like this:

a=fmtp:4 bitrate=6.3;annexa=yes

Or for G.729:

a=fmtp:18 annexb=yes

Or for speex:

a=fmtp:105 mode=8;mode=any

Istvan
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