Parameter: Codecs selection mode

This controls which codecs are offered to call legs:

• All codecs: Keep all codecs in the SDPs, including those only known by one of the two legs. This may force a call to use transcoding if one of the call legs selects a codec unknown by the other.
• Compatible codecs only: Keep only codecs known by the two call legs. This ensures low-delay relay mode can be used. Fallback to transcoding mode will still occur if no compatible codecs exist between the two call legs.
• Active codec only: Keep only the active codec, which prevent any of the two legs to change codec later during the call.