PoE Budgets And Multicast Now Decide AV Network Design

Extron published a Professional AV over IP Design Guide this month, aimed at integrators designing control rooms, corporate meeting spaces, classrooms and campus networks. The contents are unglamorous, covering layered architecture, design principles and worked system examples, which is precisely the point: after several years of buying encoders and decoders, the industry has worked out that most failed AV-over-IP projects were network design failures wearing a codec costume. The same week, PlexusAV appointed Goldenduck Group as its IPMX distributor for Thailand, another sign that open-standard AV-over-IP is being sold through conventional channel partners who will be asked to make it work on customer switches.

Power is the first constraint that bites. 802.3af gives 15.4 watts at the switch port, 802.3at gives 30, and 802.3bt reaches 60 or 90 watts. A 24-port switch rated at 470 watts of total PoE budget cannot feed twenty-four 30-watt endpoints and a handful of 90-watt devices at the same time, however confidently the port count is quoted. Devices have moved up the ladder: pan-tilt-zoom cameras with heaters, Wi-Fi 7 access points, and endpoints that charge a laptop over USB-C all sit in the 60 to 100 watt class. QNAP's new QSW-M5218P-6F12T, for example, pairs twelve 10GbE copper ports and six 25GbE SFP28 uplinks with 90 watts per port on a 470-watt budget, which is enough for a dozen 30-watt devices but not for a rack of 90-watt ones. The arithmetic has to be done per port, per switch and per UPS, with 20 to 30 per cent headroom, before the bill of materials is fixed.

Multicast and timing are the second constraint. Without IGMP snooping configured, and a querier on every VLAN that carries a stream, multicast video floods every port in the broadcast domain and the network collapses at the first busy hour. Uplinks need headroom for the sum of stream bitrates rather than the number of endpoints, which is why 10GbE and 25GbE uplinks have appeared in switches aimed at AV. Audio adds a clocking requirement: AES67 and Dante depend on IEEE 1588 precision time protocol, and switches that pass PTP with a transparent clock keep the audio aligned. Crestron's guidance for its DM NVX 370 hardware says the same thing in plainer terms: multicast and IGMP need configuring, inter-floor uplinks need headroom, and AV traffic belongs on its own VLAN or its own physical ports.

Amtune's place in that design is at the endpoints and the edge of the network. The portfolio includes AV-over-IP encoders and decoders for 1GbE distribution, AV extenders where a dedicated category-cable link is cheaper than a switch port, Dante and AES67 audio interfaces that share the same infrastructure, and HD video multi-viewers at monitoring positions. All units are built under an ISO 9001 quality system and tested to CE, FCC and RoHS. Integrators can request port, power and bandwidth planning sheets for a specific endpoint count at sales@amtune.com.