How to install the NDI SDK so libpromeki's NDI MediaIO backend builds and runs on your machine.

NDI (Network Device Interface) is a low-latency IP video / audio protocol developed by NewTek (now Vizrt). libpromeki wraps it behind the generic MediaIO interface, so application code never calls NDI directly — it just opens an NDI source / sink by URL and the backend is selected at runtime when it is enabled at build time.

The NDI SDK is distributed under a separate license from libpromeki and cannot be vendored, so it must be installed separately and pointed at via PROMEKI_NDI_SDK_DIR.

1. Download the SDK

The SDK is a free download from Vizrt but requires accepting the NDI SDK license:

https://ndi.video/for-developers/ndi-sdk/

There are two flavours, both of which libpromeki accepts:

NDI SDK — the standard SDK; runtime library is libndi.so.
NDI Advanced SDK — adds the advanced senders / receivers and additional codecs; runtime library is libndi_advanced.so.

Either ships the same headers under include/. The dynamic-load shim (Processing.NDI.DynamicLoad.h) finds whichever runtime is present, so the choice is purely a runtime / licensing decision — the build sees one consistent header set either way.

Download the Linux installer (Windows / macOS installers work on their respective platforms, same header layout), and extract / install it anywhere you like. The result looks like:

ndisdk/
  include/
    Processing.NDI.Lib.h          ← main NDI API header
    Processing.NDI.DynamicLoad.h  ← runtime library shim
    Processing.NDI.Advanced.h     ← Advanced-SDK-only extensions
    ...
  lib/
    x86_64-linux-gnu/
      libndi_advanced.so          ← runtime library (Advanced SDK)
      libndi_advanced.so.6
      libndi_advanced.so.6.2.1
    aarch64-linux-gnu/
    ...
  bin/
  documentation/

Headers live flat under include/ (no nested Interface/ directory like the NVIDIA Video Codec SDK). Per-architecture runtimes live under lib/<arch-triple>/.

2. Point libpromeki at the SDK

Pass the SDK directory at configure time:

cmake -B build -S . -DPROMEKI_NDI_SDK_DIR=/home/you/src/ndisdk

Or export it as an environment variable once:

export PROMEKI_NDI_SDK_DIR=/home/you/src/ndisdk

cmake -B build -S .

A -DPROMEKI_NDI_SDK_DIR=... on the command line always wins over the environment variable. The legacy NDI_SDK_DIR environment variable is also consulted as a find hint for compatibility with existing setups.

The CMake probe looks for include/Processing.NDI.Lib.h below that directory. If it finds the header, PROMEKI_ENABLE_NDI defaults to ON; otherwise it defaults to OFF and the backend is not built.

3. Runtime library

libpromeki uses the NDI dynamic-load shim (Processing.NDI.DynamicLoad.h), so there is nothing to link against at build time. At process startup the shim probes for libndi.so (or libndi_advanced.so) on the loader path and populates a function pointer table. If the library is not found, the NDI backend reports an error at MediaIO open time but the rest of libpromeki keeps working.

For development, the simplest setup is to add the SDK's lib/ directory to the loader path:

export LD_LIBRARY_PATH=/home/you/src/ndisdk/lib/x86_64-linux-gnu:$LD_LIBRARY_PATH

For deployment, install the runtime system-wide (the SDK installer can do this) or copy the .so into a directory listed in /etc/ld.so.conf.d/ and run sudo ldconfig.

Verify by running:

ldconfig -p | grep -E 'libndi(_advanced)?\.so'

Verification

A clean configure with everything set up correctly prints lines like these during cmake:

-- Found NDI SDK: /home/you/src/ndisdk/include

-- NDI Advanced SDK headers detected

After building, check the compiled-in features via the build-info string emitted by any libpromeki executable at startup:

Features: NETWORK PROAV ... NDI

URL form

The NDI MediaIO backend accepts two URL shapes for both source and sink mode:

ndi://<host>/<name> — <name> on <host>. For sink mode, <host> must be the local machine (NDI senders advertise from the local box); a non-local host is rejected at open with Error::InvalidArgument. For source mode, <host> filters the discovery match to that machine's canonical name.
ndi:///<name> — <name> on this machine. Equivalent to ndi://<this-host>/<name>; the local hostname is filled in automatically.

The same URL is openable for either direction. Direction is selected by the caller:

MediaIO::createForFileRead("ndi:///MyCamera") opens a receiver on <this-host> (MyCamera).
MediaIO::createForFileWrite("ndi:///MyOutput") opens a sender named MyOutput.
MediaIO::createFromUrl("ndi:///MyCamera") defaults to a receiver; pass ?OpenMode=Write to open as a sender.

NdiFactory::enumerate() returns currently-advertised sources in ndi://<host>/<name> form, so each enumerated URL round-trips through createForFileRead to the same source.

Troubleshooting

CMake cannot find the SDK

If cmake prints

-- NDI SDK not found; set PROMEKI_NDI_SDK_DIR

pass the SDK directory via -DPROMEKI_NDI_SDK_DIR=.... The directory must contain include/Processing.NDI.Lib.h; the SDK installer extracts to that layout automatically.

libndi not found at runtime

The build succeeds but opening an NDI MediaIO returns an error about the runtime library. Check:

Is libndi.so (or libndi_advanced.so, for the Advanced SDK) on the loader path? (‘ldconfig -p | grep -E 'libndi(_advanced)?.so’)
If you only have the SDK extracted (no system install), is LD_LIBRARY_PATHpointing at the SDK's lib/<arch-triple>/directory?
Is the architecture right? The SDK ships per-arch subdirectories underlib/`; pick the one that matches your build target.