# Special blocks

Media Blocks SDK .Net

Special blocks are blocks that do not fit into any other category.

The null renderer block sends the data to null. This block may be required if your block has outputs you do not want to use.

Name: NullRendererBlock.

The sample pipeline is shown below. It reads a file and sends the video data to the video samples grabber, where you can grab each video frame after decoding. The Null renderer block is used to end the pipeline.

graph LR;
    UniversalSourceBlock-->VideoSampleGrabberBlock;
    VideoSampleGrabberBlock-->NullRendererBlock;

private void Start()
{
  // create the pipeline
  var pipeline = new MediaBlocksPipeline();

  // create universal source block
  var filename = "test.mp4";
  var fileSource = new UniversalSourceBlock(await UniversalSourceSettings.CreateAsync(new Uri(filename)));

  // create video sample grabber block and add the event handler
  var sampleGrabber = new VideoSampleGrabberBlock();
  sampleGrabber.OnVideoFrameBuffer += sampleGrabber_OnVideoFrameBuffer;

  // create null renderer block
  var nullRenderer = new NullRendererBlock();

  // connect blocks
  pipeline.Connect(fileSource.VideoOutput, sampleGrabber.Input);        
  pipeline.Connect(sampleGrabber.Output, nullRenderer.Input);   

  // start the pipeline
  await pipeline.StartAsync();
}

private void sampleGrabber_OnVideoFrameBuffer(object sender, VideoFrameXBufferEventArgs e)
{
    // received new video frame
}

Windows, macOS, Linux, iOS, Android.

The tee block splits the video or audio data stream into multiple streams that completely copy the original stream.

Name: TeeBlock.

graph LR;
    UniversalSourceBlock-->TeeBlock;
    TeeBlock-->VideoRendererBlock;
    TeeBlock-->H264EncoderBlock;
    H264EncoderBlock-->MP4SinkBlock;

var pipeline = new MediaBlocksPipeline();

var filename = "test.mp4";
var fileSource = new UniversalSourceBlock(await UniversalSourceSettings.CreateAsync(new Uri(filename)));

var videoTee = new TeeBlock(2);
var h264Encoder = new H264EncoderBlock(new OpenH264EncoderSettings());
var mp4Muxer = new MP4SinkBlock(new MP4SinkSettings(@"output.mp4"));
var videoRenderer = new VideoRendererBlock(pipeline, VideoView1);

pipeline.Connect(fileSource.VideoOutput, videoTee.Input);
pipeline.Connect(videoTee.Outputs[0], videoRenderer.Input);
pipeline.Connect(videoTee.Outputs[1], h264Encoder.Input);
pipeline.Connect(h264Encoder.Output, mp4Muxer.CreateNewInput(MediaBlockPadMediaType.Video));

await pipeline.StartAsync();

• Simple Capture Demo

Windows, macOS, Linux, iOS, Android.

The Super MediaBlock allows you to combine multiple blocks into a single block.

Name: SuperMediaBlock.

graph LR;
    VirtualVideoSourceBlock-->SuperMediaBlock;
    SuperMediaBlock-->NullRendererBlock;

Inside the SuperMediaBlock:

graph LR;
    FishEyeBlock-->ColorEffectsBlock;

Final pipeline:

graph LR;
    VirtualVideoSourceBlock-->FishEyeBlock;
    subgraph SuperMediaBlock
    FishEyeBlock-->ColorEffectsBlock;
    end
    ColorEffectsBlock-->NullRendererBlock;

var pipeline = new MediaBlocksPipeline();

var videoViewBlock = new VideoRendererBlock(pipeline, VideoView1);

var videoSource = new VirtualVideoSourceBlock(new VirtualVideoSourceSettings());

var colorEffectsBlock = new ColorEffectsBlock(VisioForge.Core.Types.X.VideoEffects.ColorEffectsPreset.Sepia);
var fishEyeBlock = new FishEyeBlock();

var superBlock = new SuperMediaBlock();
superBlock.Blocks.Add(fishEyeBlock);
superBlock.Blocks.Add(colorEffectsBlock);
superBlock.Configure(pipeline);

pipeline.Connect(videoSource.Output, superBlock.Input);
pipeline.Connect(superBlock.Output, videoViewBlock.Input);

await pipeline.StartAsync();

Windows, macOS, Linux, iOS, Android.

The AESCipher enum defines the types of AES ciphers that can be used. (Source: VisioForge.Core/Types/X/Special/AESCipher.cs)

• AES_128: AES 128-bit cipher key using CBC method.
• AES_256: AES 256-bit cipher key using CBC method.

Windows, macOS, Linux, iOS, Android.

The EncryptorDecryptorSettings class holds settings for encryption and decryption operations. (Source: VisioForge.Core/Types/X/Special/EncryptorDecryptorSettings.cs)

• Cipher (AESCipher): Gets or sets the AES cipher type. Defaults to AES_128.
• Key (string): Gets or sets the encryption key.
• IV (string): Gets or sets the initialization vector (16 bytes as hex).
• SerializeIV (bool): Gets or sets a value indicating whether to serialize the IV.

• EncryptorDecryptorSettings(string key, string iv): Initializes a new instance with the given key and initialization vector.

Windows, macOS, Linux, iOS, Android.

The CustomMediaBlockPad class defines information for a pad within a CustomMediaBlock. (Source: VisioForge.Core/Types/X/Special/CustomMediaBlockPad.cs)

• Direction (MediaBlockPadDirection): Gets or sets the pad direction (input/output).
• MediaType (MediaBlockPadMediaType): Gets or sets the media type of the pad (e.g., Audio, Video).
• CustomCaps (Gst.Caps): Gets or sets custom GStreamer capabilities for an output pad.

• CustomMediaBlockPad(MediaBlockPadDirection direction, MediaBlockPadMediaType mediaType): Initializes a new instance with the specified direction and media type.

Windows, macOS, Linux, iOS, Android.

The CustomMediaBlockSettings class provides settings for configuring a custom media block, potentially wrapping GStreamer elements. (Source: VisioForge.Core/Types/X/Special/CustomMediaBlockSettings.cs)

• ElementName (string): Gets the name of the GStreamer element or Media Blocks SDK element. To create a custom GStreamer Bin, include square brackets, e.g., "[ videotestsrc ! videoconvert ]".
• UsePadAddedEvent (bool): Gets or sets a value indicating whether to use the pad-added event for dynamically created GStreamer pads.
• ElementParams (Dictionary<string, object>): Gets the parameters for the element.
• Pads (List<CustomMediaBlockPad>): Gets the list of CustomMediaBlockPad definitions for the block.
• ListProperties (bool): Gets or sets a value indicating whether to list element properties to the Debug window after creation. Defaults to false.

• CustomMediaBlockSettings(string elementName): Initializes a new instance with the specified element name.

Windows, macOS, Linux, iOS, Android.

The InputSelectorSyncMode enum defines how an input-selector (used by SourceSwitchSettings) synchronizes buffers when in sync-streams mode. (Source: VisioForge.Core/Types/X/Special/SourceSwitchSettings.cs)

• ActiveSegment (0): Sync using the current active segment.
• Clock (1): Sync using the clock.

Windows, macOS, Linux, iOS, Android.

The SourceSwitchSettings class configures a block that can switch between multiple input sources. (Source: VisioForge.Core/Types/X/Special/SourceSwitchSettings.cs)

The summary "Represents the currently active sink pad" from the code comment might be slightly misleading or incomplete for the class name SourceSwitchSettings. The properties suggest it's for configuring a source switcher.

• PadsCount (int): Gets or sets the number of input pads. Defaults to 2.
• DefaultActivePad (int): Gets or sets the initially active sink pad.
• CacheBuffers (bool): Gets or sets whether the active pad caches buffers to avoid missing frames when reactivated. Defaults to false.
• DropBackwards (bool): Gets or sets whether to drop buffers that go backwards relative to the last output buffer pre-switch. Defaults to false.
• SyncMode (InputSelectorSyncMode): Gets or sets how the input-selector syncs buffers in sync-streams mode. Defaults to InputSelectorSyncMode.ActiveSegment.
• SyncStreams (bool): Gets or sets if all inactive streams will be synced to the running time of the active stream or to the current clock. Defaults to true.
• CustomName (string): Gets or sets a custom name for logging purposes. Defaults to "SourceSwitch".

• SourceSwitchSettings(int padsCount = 2): Initializes a new instance, optionally specifying the number of pads.

Windows, macOS, Linux, iOS, Android.