NDI Bandwidth Explained

Quick Answer

NDI High Bandwidth usually needs the most bandwidth, HX3 usually lands in a middle ground, and HX2 is typically the lowest-bitrate option but also the least suitable for latency-sensitive production. Exact numbers depend on resolution, frame rate, image complexity, vendor implementation, and how many receivers you need to serve.

Why It Happens

NDI bandwidth is driven by three things: the NDI format, the resolution and frame rate, and the number of copies the network has to carry. NDI High Bandwidth and the NDI HX formats are not interchangeable planning targets, because they use different compression approaches and behave differently under load.

Unlike SMPTE 2110, which is built around uncompressed essences on larger managed IP fabrics, NDI is designed to be practical on standard Ethernet networks. That makes it flexible, but it also means you need to think in ranges and headroom rather than assuming one fixed Mbps value always applies.

NDI Formats at a Glance

NDI Format	Codec	1080p60 Bandwidth	Latency	Best For
NDI High Bandwidth (HB)	Production-oriented compression	Typical 125-150 Mbps planning range	Typical low-latency production range	Production, switching, monitoring
NDI HX3	H.264 or H.265 (implementation-dependent)	Typical compressed mid-range	Typical lower-latency compressed range	PTZ cameras, 1G constrained networks
NDI HX2	H.264 or H.265 (implementation-dependent)	Typical low-bitrate range	Typical higher-latency monitoring range	Monitoring, proxy, distribution

NDI High Bandwidth

NDI High Bandwidth is the highest-bandwidth NDI option and is usually the easiest fit for switching, multiview, and other low-latency production tasks. It is commonly planned in roughly the 125-150 Mbps range for 1080p60, but the real value varies with format and implementation.

That makes NDI High Bandwidth practical for production, but expensive in uplink budget. If you are mixing NDI with other streaming protocols, use our Video Bitrate Calculator to compare the order of magnitude against other delivery paths.

NDI HX3

HX3 usually sits in the middle ground between NDI High Bandwidth and HX2. It is often a practical choice for PTZ cameras and bandwidth-constrained 1 GbE workflows, but its bitrate and latency behavior depend on the device, firmware, encoder settings, and how aggressively the system is compressing.

In practice, HX3 is best treated as a planning range rather than a guaranteed one-frame answer. Test the actual camera and receiver pair you intend to use before treating it as live-switching-safe.

NDI HX2

HX2 is the lowest-bandwidth option of the three and is often used where distribution efficiency matters more than production latency. That can make it useful for monitoring, campus distribution, and proxy-style workflows.

For live switching, IFB-like monitoring, or anything timing-sensitive, HX2 is usually a poor fit unless the whole pipeline has been tested and accepted for the extra delay.

How to Plan NDI Bandwidth

A practical rule for NDI planning is to leave headroom rather than running every switch uplink at its theoretical maximum. The linked planner uses visible utilisation thresholds as planning conventions, not as NDI limits. Choose the operating margin from the real switch design, traffic pattern, telemetry, and failure tolerance.

For real deployments, model the topology rather than guessing from camera count. Use the NDI Network Planner to estimate mixed-codec topologies. The separate ST 2110 Video Capacity Worksheet is only for uncompressed ST 2110 active-image planning.

Unicast vs. Multicast in NDI

Many NDI deployments are planned around unicast. In unicast, each receiver gets its own copy of the stream, so receiver count matters just as much as source count. One source to one destination is a very different network problem than one source to ten destinations.

Multicast can reduce repeated sender load when the same stream must reach many receivers, but it only helps if the switch fabric is configured correctly. Without IGMP Snooping and a working querier, multicast can create a mess rather than solve one.

Configuring NDI Multicast

1. Enable multicast only where the sender and current NDI implementation support it, following the source-vendor and NDI documentation.
2. On your managed switch, enable IGMP Snooping on the VLAN carrying NDI traffic. Without IGMP Snooping, multicast behaves like broadcast — flooding all ports and defeating the bandwidth benefit.
3. Configure an IGMP Querier (typically the switch's Layer 3 interface or a dedicated multicast router) to periodically poll group membership and prevent stale multicast forwarding entries.
4. Assign a dedicated VLAN for NDI multicast traffic, separate from management and general data traffic, to prevent multicast flooding from affecting other devices.

How to Use This in a Real Workflow

1. Pick the NDI variant that matches your latency and quality target, not just the lowest Mbps number.
2. Count receivers as well as sources, especially in unicast topologies.
3. Leave headroom on switch uplinks instead of planning to the theoretical maximum.
4. Test multicast behavior before relying on it in production.

NDI Discovery: mDNS, Discovery Server, and Access Manager

NDI uses Multicast DNS (mDNS) for automatic source discovery on the local network. mDNS is a zero-configuration protocol — NDI sources advertise themselves and receivers discover them without any server infrastructure. However, mDNS is limited to the local subnet and does not cross router boundaries.

For routed or multi-subnet environments, NDI Discovery Server is the registry-based alternative to mDNS described by NDI. NDI Access Manager is a configuration application that can point supported systems at a Discovery Server and add remote sources or groups; it is not itself the central registry service. Verify platform availability and the current NDI Tools documentation before deployment.

Common Mistakes

• Treating one published Mbps number as a fixed promise for every device and every picture type.
• Counting sources but ignoring receiver fan-out on unicast networks.
• Assuming multicast helps automatically without IGMP Snooping and a querier.
• Using NDI HX formats for low-latency production without testing the exact sender/receiver path.

References

• NDI Documentation: Understanding NDI Formats
• NDI Documentation: Multicast
• NDI Documentation: Discovery and Terminology