[opus] Codec setting using fmtp maxaveragebitrate and OPUS_SET_BITRATE

Julien Chavanton jchavanton at gmail.com
Mon Oct 27 07:13:30 PDT 2014


Hi Folks,  thanks for the great work, not sure if this is the right list
for this type of quesiton.

We are looking to use only Opus as "one codec for all", with VoIP-out
obviously we want to tune it.

I am planning to use fmtp in SDP to control server/client Opus settings.

Something like :

   - *maxplaybackrate*: a hint about the maximum output sampling rate that
   the receiver is capable of rendering in Hz.
   maxplaybackrate=8000

   - *maxaveragebitrate*: specifies the maximum average receive bitrate of
   a session in bits per second (b/s).
   maxaveragebitrate=12000


I have a question about the documentation :

"RTP Payload Format for Opus Speech and Audio Codec
draft-spittka-payload-rtp-opus-03

maxaveragebitrate : Any positive integer is allowed but values outside the
range between 6000 and 510000 SHOULD be ignored."

If I understand, maxaveragebitrate" could/should be use with
OPUS_SET_BITRATE


However when looking at "opus_encoder_ctl"  OPUS_SET_BITRATE documentation
I see :
"Configures the bitrate in the encoder. Rates from 500 to 512000 bits per
second are meaningful"

-------------------------------------------------------------------

I suppose "500", is an error in the documentation and it should be "6000" ?

"Bit-rates from 6 kb/s to 510 kb/"


Thanks
Julien






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