The Opus codec arguably delivers the best audio quality and lowest delay. While the difference is negligible when compared to some members of the AAC family, there are other significant benefits.

• EBU 3326 relies on the SIP protocol, which is the standard for VoIP telephony. Within that ecosystem, Opus has already been widely adopted, whereas few practical implementations of the common AoIP codecs exist. Due to a lack of references and clear definitions, the various approaches taken by manufactures are sometimes incompatible.
• Opus was made for the Internet. It employs forward error correction to account for the unreliable nature of the Internet. AAC offers some resilience, but other common AoIP codecs do not.
• Opus is versatile. Without relying on different versions, it is always low delay, supports all common sample rates, works well over a wide range of bitrates, and can transport up to 255 channels of audio.
• Opus is not burdened by patents. Off-the-shelf open source libraries exist, allowing for easy integration without the headaches of license agreements.

With ISDN, interoperability has always been hampered by the wide and varied range of codecs offered by different hardware. A standard method of offering and agreeing on a common codec has never been widely adopted. With SIP, such a method exists through the SDP (Session Description Protocol), but chances of success are greatly increased when a standard default codec is offered. It is our opinion, that Opus is the most appropriate choice as a default and preferred codec.