AES67 and AoIP Interoperability
Definition
Audio over IP developed as several systems from different makers, including Dante, Ravenna, Livewire and Q-LAN, and a device on one system could not exchange audio with a device on another. AES67, first published by the Audio Engineering Society in 2013, defines a common interoperability mode that these systems can implement alongside their native mode. It specifies how the audio is packetised (RTP), how clocks are synchronised and how a stream is described (SDP), so that a Ravenna source and a Dante receiver can exchange channels directly.
The guide
AES67 deliberately leaves discovery out of its requirements. Each system uses its own method, such as SAP announcements or manual entry of the stream description, so connecting two brands often needs manual configuration or a management tool.
Clocking is the base of the interoperability. AES67 uses PTP version 2 (IEEE 1588-2008) and defines a media profile, while support for the default PTP profile is mandatory. Native Dante runs on PTPv1 and adds PTPv2 in AES67 mode, so all the devices are brought into one PTP domain with a single leader clock. A clock mismatch produces the same clicks and dropouts as any other timing fault, this time at the boundary between the two systems.
AES67 requires support for 48 kHz and a packet time of 1 ms, with 44.1 and 96 kHz optional, and carries the audio as RTP. SMPTE ST 2110-30, the audio part of broadcast IP video, references AES67 and adds constraints such as the SMPTE ST 2059-2 PTP profile. Two systems that both support AES67 exchange audio once their sample rate, packet time and PTP settings agree, and the link is then checked on both sides.
The rule
Two AES67 systems exchange audio once they share one PTP clock, one sample rate and one packet time.
Glossary terms
Sources
- AES67 (pointeur Wikipédia) : publiée en 2013 ; RTP, SDP, PTPv2 (IEEE 1588-2008), 48 kHz obligatoire, 44,1 et 96 kHz optionnels, paquet de 1 ms · en.wikipedia.org
- RAVENNA / The Broadcast Bridge, Your practical guide to AES67, part 1 : découverte exclue des exigences, SAP comme option ; profil PTP par défaut obligatoire · ravenna-network.com
- AIMS Alliance, AES67 / SMPTE ST 2110 Commonalities and Constraints : ST 2110-30 s'appuie sur AES67, profil ST 2059-2 · aimsalliance.org
- Audinate, The Relationship Between Dante, AES67 and SMPTE ST 2110 : Dante en PTPv1, PTPv2 en mode AES67 · go.audinate.com
- Audinate, Dante Controller User Guide, Clock Synchronization : PTP IEEE 1588, élection d'une horloge leader, suiveurs · dev.audinate.com