Multicast Transmit Flow Configuration

Click the 'Create a new multicast flow' button in Device View to open the Create Multicast Flow dialog.

The dialog displays a list of the Tx channels for the device.

To add channels to a multicast flow, select the checkboxes for the channel name. Once you have selected all the channels required, create the multicast flow by clicking the Create button at the bottom of the dialog box. To abandon creating a new multicast flow, click Cancel.

Once a flow has been created, it will appear in the list of flows in the transmit pane, along with the channels contained within that flow. Channels cannot be added to or removed from existing flows. Each time the dialog is used to select additional channels, a new multicast flow will be created.

By default, Dante receivers will connect to a multicast flow if one exists that contains the required channel(s), rather than creating a new unicast flow.

If a channel that does not form part of an existing multicast flow is added to a new multicast flow, any existing unicast subscriptions to that channel will automatically switch over to use the new multicast flow.

A good rule of thumb is to use multicast when there are more than two receivers for a specific audio channel. You should also assume that the flow will flood throughout the entire network, and therefore consume bandwidth on all network links.

Maximum Channels per Flow

The number of channels that can be added to a Dante multicast flow varies by device type. This is displayed at the top of this window, and is 64 channels for the device shown above.

If you select more channels than the maximum supported channels per flow, multiple flows will be created. For supporting devices, you can restrict flows to fewer channels if required, using the drop-down menu in the Flow Config section.

Managing Flow Size

Multicast flows propagate through the network to every device that requests one or more of the channels in the flow. When considering network traffic management, in a typical network where no devices actually need all channels, it would be more advisable to create multiple flows than it would to create one flow containing all channels.

In the first example illustrated below, one multicast flow was created, containing four channels. None of the devices actually require all four channels, but both switches are processing four channels of traffic.

In the second example, two flows were created with two channels each. All devices are receiving the channels they need, but the switches are processing half the traffic.

Figure 1 - Single multicast flow with all channels

Figure 2 - Two multicast flows, with half the number of channels in each

Deleting Multicast Flows

Care should be taken when deleting a multicast flow, as the existing subscriptions will convert back to unicast. This has the potential to result in exceeding the link capacity or maximum number of flows at the transmit device, as multiple unicast flows will be established between the transmitter and its receivers. It may be advisable to remove some or all of the audio routes prior to deleting the multicast flow.

Note:  Certain Ethernet switches support IGMP (Internet Group Management Protocol), a protocol that provides the ability to 'prune' multicast traffic, so that it travels only to those end destinations that require that traffic. If this is the case, and IGMP is correctly configured on all the Ethernet switches, then multicast audio will not flood throughout the network, but will instead be sent only over the links required to deliver it to subscribed devices.

AES67 Flow

The AES67 Flow option is only available for AES67-enabled devices.

When AES67 Flow is checked, the selected channels will be added to an AES67 multicast flow. Only AES67-enabled devices can receive AES67 flows. Dante devices cannot subscribe to AES67 flows from other Dante devices.

RTP transmit flows (including AES67 flows) from non-Dante devices appear in blue at the far right of the Routing tab of the Network View, and at the bottom of the Available Channels list in the Device View > Receive tab. AES67 flows are identified by their transmit multicast IP addresses, rather than device names.

For AES67-enabled Dante devices, each device transmit channel can simultaneously support an AES67 multicast flow and a standard Dante multicast flow.

AES67 flows support 8 channels. If more than 8 channels are selected for an AES67 flow, multiple flows will be created.

SMPTE Flows

For DDM networks, supporting devices that are enrolled in a SMPTE-enabled domain can transmit and subscribe to SMPTE ST 2110-30 flows.

Creating SMPTE Flows

SMPTE flows created in Dante Controller are advertised on the network via SAP/SDP.

Note:  Refer to the SMPTE Standard (SMPTE ST 2110 -30:2017) for more information about SMPTE audio. Refer to the DDM User Guide for information about configuring RTP domains.

To create a SMPTE flow:

  1. Open the Device View for the device and click the 'Create a new multicast flow' button.
  2. Select the required SMPTE flow config.

    • SMPTE A: 48 kHz flow with up to 8 channels at packet times of 1ms
    • SMPTE B: 48 kHz flow with up to 8 channels at packet times of 125μs
    • SMPTE C: 48 kHz flow with 64 channels at packet times of 125μs
  3. For the Destination Address:

    • Select 'Auto' to automatically assign the destination address and port number. The destination address will be assigned according to the RTP prefix configured for the domain in which the device is enrolled. For example, if the RTP prefix for the domain is 69, the device will create a flow with destination address of 239.69.x.x. The port number defaults to 5004.
    • Select 'Manual' to specify the address and port. The IP address must be in the range 239.0.0.0 to 239.254.254.254. The port can be set to any non-administrative port number.
  4. Select the channels to be added to the flow, and click ‘Create’. If the number of selected channels exceeds the maximum number supported by the config, multiple flows will be created.

The transmit flow will present in the controller software for your SMPTE receiver if it natively supports SAP/SDP parsing. If not, an alternative mechanism will be required to parse the SDP descriptor for the flow. The configuration of third-party SMPTE receivers is specific to the receiver.

Note:  Renaming a Dante device will also rename any SMPTE flows from that device.

Subscribing to SMPTE Flows

SMPTE transmit flows from non-Dante devices present in Dante Controller as Dante transmitters with blue 'device' names. The device name is taken from the SDP descriptor for the flow as advertised by the device, or configured in Dante Domain Manager.

SMPTE channels can be subscribed to (by supporting devices) in the same way as channels from other transmitters.

If the transmitter does not advertise flows via SAP/SDP, you can use DDM to generate a 'proxy' RTP session with a descriptor that is supported by Dante Controller.

Note:  The PTP v2 clock domain configured for the domain in DDM must match that of the flow. If they do not match, when you attempt to subscribe to the flow, Dante Controller will report 'Clock domain mismatch'.
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Note:  The RTP Prefix configured for the domain in DDM must match that of the flow. If they do not match, subscriptions will appear to succeed but audio will not flow.

For more information about SMPTE domain configuration and SDP descriptors, refer to the DDM user guide.