Table of Contents

Class NDISourceBlock

Namespace
VisioForge.Core.MediaBlocks.Sources
Assembly
VisioForge.Core.dll

NDI (Network Device Interface) source block for professional IP-based video streaming. Provides low-latency, high-quality video and audio streaming over IP networks for broadcast production, live events, and multi-camera setups with automatic source discovery and synchronization capabilities. Implements the VisioForge.Core.MediaBlocks.Sources.SourceMediaBlock. Implements the VisioForge.Core.MediaBlocks.IMediaBlockInternals. Implements the IDisposable.

public sealed class NDISourceBlock : SourceMediaBlock, IMediaBlock, IDisposable, IMediaBlockInternals, IGetVideoStreamInfo

Inheritance

Implements

Inherited Members

Extension Methods

Constructors

NDISourceBlock(NDISourceSettings)

Initializes a new instance of the VisioForge.Core.MediaBlocks.Sources.NDISourceBlock class with custom NDI settings. Configures the NDI source for professional IP video streaming with specified parameters.

public NDISourceBlock(NDISourceSettings settings)

Parameters

settings NDISourceSettings

The NDI settings controlling source selection, bandwidth, and connection parameters. Must not be null.

Remarks

Round-3 LOW #376: validate settings in the ctor instead of deferring to Build. The previous behaviour silently accepted null and allocated VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.VideoOutput, VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.AudioOutput, and the _outputs cache for a block that Build would later refuse to initialise — wasting work and leaving the block in an obviously unusable state with no early failure signal. Failing fast in the ctor surfaces the misuse at the call site rather than at the (much later) Build call.

Exceptions

ArgumentNullException

Thrown when settings is null.

Properties

AudioOutput

Gets the audio output pad that provides NDI audio stream to downstream blocks.

public MediaBlockPad AudioOutput { get; }

Property Value

MediaBlockPad

Input

Gets the primary input pad (none for source blocks that receive network streams).

public override MediaBlockPad Input { get; }

Property Value

MediaBlockPad

Inputs

Gets all input pads available on this block (none for source blocks).

public override MediaBlockPad[] Inputs { get; }

Property Value

MediaBlockPad[]

Output

Gets the primary output pad — video when present, otherwise audio for audio-only NDI sources. Returning VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.VideoOutput unconditionally gave audio-only sources a useless dangling pad and broke single-output callers that expected the primary pad to actually carry data.

public override MediaBlockPad Output { get; }

Property Value

MediaBlockPad

Remarks

Thread-safety contract (Round-3 MEDIUM #258): this getter is NOT synchronised against a concurrent VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.CleanUp. The VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.VideoOutput / VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.AudioOutput property references are immutable for the block's lifetime, but the Gst.Pad inside each MediaBlockPad is mutated by SetInternalPad from VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.Build / VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.CleanUp. A reader that observes !IsInternalPadNull() here can race a concurrent CleanUp that nulls the internal pad before the caller links into it. Callers MUST re-check IsInternalPadNull() on the returned pad themselves (and treat null-pad as a no-op) when concurrent CleanUp is possible — or hold whatever pipeline-level lock guards their build/teardown ordering.

Outputs

Gets all output pads available on this block (video and audio outputs).

public override MediaBlockPad[] Outputs { get; }

Property Value

MediaBlockPad[]

Remarks

Backed by VisioForge.Core.MediaBlocks.Sources.NDISourceBlock._outputs — populated once in the ctor (after VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.VideoOutput/VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.AudioOutput are assigned) and returned on every read so we don't allocate a new array per call. The pad references themselves are immutable for the block's lifetime (the underlying Gst.Pad inside each MediaBlockPad swaps via SetInternalPad, but the pad wrapper instances do not), so the cached array stays valid across Build / CleanUp cycles.

Round-3 MEDIUM #260: outside the built state we return Empty<T>() instead of the cached array. The cached pads still exist but their internal Gst.Pad has been nulled by VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.CleanUp; pipeline traversal that links them post-CleanUp would silently fail because GetInternalPad() returns null. Returning an empty array makes the post-CleanUp / pre-Build state observable to callers without exposing stale pads.

Settings

Gets or sets the NDI configuration settings that control source selection and stream parameters.

public NDISourceSettings Settings { get; set; }

Property Value

NDISourceSettings

Remarks

Round-3 MEDIUM #259: the setter throws InvalidOperationException when invoked after VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.Build has succeeded. The underlying NDISource (desktop) or NDIAndroidReceiver (Android) is constructed against the snapshot of Settings at Build-time and does not pick up post-Build mutations. Allowing the property to be reassigned silently kept the receiver capturing from the old source while the property reported the new one — a confusing diagnosis trap. To change settings on a built block, dispose it and create a new one.

Type

Gets the media block type identifier for NDI source operations.

public override MediaBlockType Type { get; }

Property Value

MediaBlockType

VideoOutput

Gets the video output pad that provides NDI video stream to downstream blocks.

public MediaBlockPad VideoOutput { get; }

Property Value

MediaBlockPad

Methods

Build()

Builds and initializes the NDI source within the pipeline context. Connects to NDI stream, configures video/audio outputs, and prepares synchronized playback for downstream processing.

public override bool Build()

Returns

bool

true if the NDI source was successfully built and configured; otherwise, false.

CleanUp()

Cleans up all resources associated with the NDI operations, including network connections and stream buffers.

public void CleanUp()

Dispose(bool)

Releases unmanaged and managed resources used by the NDI source. Properly closes network connections and disposes of GStreamer elements and streaming resources.

protected override void Dispose(bool disposing)

Parameters

disposing bool

true to release both managed and unmanaged resources; false to release only unmanaged resources.

GetCore()

Gets the core GStreamer element wrapper for advanced configuration and monitoring.

public BaseElement GetCore()

Returns

BaseElement

The underlying VisioForge.Core.GStreamer.Sources.NDISource wrapper on desktop, or null on Android (composite block) and before VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.Build / after VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.CleanUp.

Remarks

Round-3 MEDIUM #264: returns the underlying VisioForge.Core.GStreamer.Sources.NDISource on desktop platforms (it is a single-element source so the wrapper is the well-defined "core") and null on Android, where the block is composed of a VisioForge.Core.MediaBlocks.Sources.CustomMixerSourceBlock plus a native receiver thread and has no single underlying element. The previous implementation returned null on every platform, which broke the documented contract that source blocks expose their underlying element for advanced configuration.

GetElement()

Gets the native GStreamer element for direct GStreamer pipeline integration.

public Element GetElement()

Returns

Element

The NDI source GStreamer element on desktop platforms (or null when the block is not in the built state), or null on Android.

Remarks

Platform contract:

  • Desktop (Windows / Linux / macOS / iOS): returns the underlying ndisrc GStreamer element after a successful VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.Build. Returns null before VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.Build has run or after VisioForge.Core.MediaBlocks.Sources.NDISourceBlock.CleanUp has torn the source down (Round-3 MEDIUM #263).
  • Android: ALWAYS returns null. The Android implementation is a composite of VisioForge.Core.MediaBlocks.Sources.CustomMixerSourceBlock (two appsrc elements) plus a native NDI receiver thread; there is no single Gst.Element that represents the whole block. Callers MUST null-check the return value or branch on OperatingSystem.IsAndroid() / #if __ANDROID__ before dereferencing.

GetVideoStreamInfo()

Returns the probed NDI video stream info when available.

public VideoStreamInfo GetVideoStreamInfo()

Returns

VideoStreamInfo

Video stream metadata, or null when the source has no video info yet.

IsAvailable()

Determines whether NDI support is available on the current system. Requires NDI runtime and GStreamer NDI plugins to be installed and licensed. On Android availability depends on libndi.so being shipped with the app AND the appsrc GStreamer factory being registered. The libndi presence check is cached after the first call so subsequent calls are free.

public static bool IsAvailable()

Returns

bool

true if NDI support is available; otherwise, false.

Stop()

Stops the desktop NDI source. Round-3 MEDIUM #143: desktop ndisrc element auto-stops via the GStreamer state change, but providing an override gives MediaBlocksPipeline.Stop a hook for future bookkeeping symmetric with the Android path. Currently routes straight to base.Stop().

public override bool Stop()

Returns

bool

IMediaBlockInternals.SetContext(MediaBlocksPipeline)

Sets the pipeline context for this NDI source, providing access to the parent pipeline and logging context.

void IMediaBlockInternals.SetContext(MediaBlocksPipeline pipeline)

Parameters

pipeline MediaBlocksPipeline

The parent MediaBlocks pipeline containing this NDI source.

See Also