VAST.UI for WPF

The VAST.UI for WPF library provides media player controls for Windows Presentation Foundation applications. It supports hardware-accelerated DirectX 11 rendering with WriteableBitmap fallback, and implements the IMediaPlayer interface for unified playback control.

Overview

Feature	Description
DirectX 11 Rendering	Hardware-accelerated video rendering via DirectX 11
WriteableBitmap Fallback	CPU-based rendering when DirectX is unavailable
Mouse Controls	Pan/tilt via drag, zoom via mouse wheel
Subtitles	Configurable subtitle rendering with font and color options
Overlays	BitmapSource overlay support for custom graphics on video
Snapshots	Capture current video frame as JPEG
XAML Support	Declarative UI with data binding support

Requirements

• .NET: .NET 6.0+ or .NET Framework 4.5.2+
• Dependencies: VAST.Common, VAST.Common.Ext.Win32

Setup

Add the MediaPlayerControl or VideoPreviewControl to your window using XAML or programmatically:

<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vast="clr-namespace:VAST.Controls;assembly=VAST.UI">
    <vast:MediaPlayerControl x:Name="player" />
</Window>

var player = new VAST.Controls.MediaPlayerControl();
this.Content = player;

MediaPlayerControl

The MediaPlayerControl is the primary control for video playback in WPF applications.

XAML Usage

<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vast="clr-namespace:VAST.Controls;assembly=VAST.UI">
    <vast:MediaPlayerControl x:Name="player" />
</Window>

Code Usage

// Set media source
player.Source = new Uri("rtsp://camera.example.com/stream");

// Control playback
player.Play();
player.Pause();
player.Stop();

// Adjust volume
player.Volume = 0.8f;
player.IsMuted = false;

// Enable interactive pan/tilt/zoom
player.PlaybackParameters = new PlaybackParameters
{
    AllowDigitalPTZ = true,
};

Playback Properties

Property	Type	Description
AbsolutePlaybackTime	DateTime?	Absolute playback time for live streams with embedded timestamps
AutoPlay	bool	Auto-start on media load
Balance	float	Audio balance (-1.0 to 1.0)
CanPause	bool	Media supports pausing
CanSeek	bool	Media supports seeking
CurrentState	PlayerState	Current playback state
CurrentStatistics	NetworkStat	Real-time network performance statistics
Duration	TimeSpan	Total media duration
EchoCanceller	IEchoCanceller	Echo canceller for two-way audio communication
IsFullScreen	bool	Full-screen mode state
IsLooping	bool	Loop playback at end
IsMuted	bool	Audio mute state
PlaybackParameters	PlaybackParameters	Rendering and other low level configuration
PlaybackRate	double	Playback speed (1.0 = normal)
Position	TimeSpan	Current playback position
Source	Uri	Media source URI
SourceMedia	IMediaSource	Custom media source object
Stretch	StretchType	Video stretch mode
SubtitleDecoration	SubtitleDecoration	Subtitle font, size, and color configuration
Volume	float	Audio volume (0.0 to 1.0)

Stream Selection

Property	Type	Description
AudioStreamCount	int	Number of audio streams
AudioStreamIndex	int	Selected audio stream
VideoStreamCount	int	Number of video streams
VideoStreamIndex	int	Selected video stream
SubtitleStreamCount	int	Number of subtitle streams
SubtitleStreamIndex	int	Selected subtitle stream

Display Properties

Property	Type	Default	Description
PlayerBackgroundColor	string		Background color in #ARGB format

Events

Event	Description
CurrentStateChanged	Playback state changed
MediaEnded	Playback reached end
MediaFailed	Error occurred
MediaOpened	Media loaded successfully
SeekCompleted	Seek operation finished
VideoRenderingStarted	First frame rendered

Methods

Method	Description
GetAudioMediaType	Get audio stream format
GetSubtitleMediaType	Get subtitle stream format
GetVideoMediaType	Get video stream format
Pause	Pause playback
Play	Start or resume playback
Stop	Stop playback and release resources
TakeSnapshot	Capture current frame as JPEG (returns Task<Stream>)
SetOverlay	Set overlay bitmap on video (Pbgra32 or Bgra32)
RemoveOverlay	Remove overlay from video

Playback Parameters

Configure low-level playback behavior using PlaybackParameters:

player.PlaybackParameters = new PlaybackParameters
{
    RenderingStrategy = RenderingStrategy.LowLatency,
    VideoRendererType = VideoRendererType.Auto,
    AllowDigitalPTZ = true,
};

Parameter	Type	Default	Description
AllowDigitalPTZ	bool	false	Enable pan, tilt, and zoom via mouse gestures
AllowIncompleteMediaType	bool?	null	Start playback before all stream types are detected
AudioDecoderParameters	DecoderParameters		Audio decoder configuration
AudioOutputDeviceId	string	null	WASAPI audio output device identifier
CleanupOnStop	bool	true	Clear video surface when playback stops
ForceKeyframeOnlyDecoding	bool	false	Decode keyframes only; reduces CPU/GPU load but video updates only at GOP intervals
MirrorX	bool	false	Flip video horizontally
MirrorY	bool	false	Flip video vertically
RenderingStrategy	RenderingStrategy	LowLatency	LowLatency renders frames immediately; Smooth uses timestamp-based timing
StopAfterFirstFrame	bool	false	Stop playback after rendering the first frame
StopAfterLastFrame	bool	true	Stop playback after rendering the last frame
VideoDecoderParameters	DecoderParameters		Video decoder configuration
VideoRendererType	VideoRendererType	Auto	Auto selects best available; Best forces DirectX; Compatible uses WriteableBitmap
VideoRenderingFramerate	Rational	null	Maximum rendering framerate; null renders all frames

Playback Rates

Playback rate control is only available for interactive sources (VOD, file-based media). Live streams do not support playback rate changes.

Rate	Description
-32 to -1	Rewind (backward playback)
0 to 1 (exclusive)	Slow motion
1	Normal speed
1 to 32	Fast forward

Mouse Gestures

When PlaybackParameters.AllowDigitalPTZ is enabled, the control supports interactive pan, tilt, and zoom.

Input	Action
Mouse drag	Pan/tilt (cursor changes to ScrollAll)
Mouse wheel	Zoom in/out centered on cursor position

player.PlaybackParameters = new PlaybackParameters
{
    AllowDigitalPTZ = true,
};

Overlays

Display custom graphics over the video using BitmapSource overlays:

// Create overlay bitmap (must be Pbgra32 or Bgra32)
var bitmap = new WriteableBitmap(width, height, 96, 96, PixelFormats.Pbgra32, null);

// Draw on the bitmap
bitmap.Lock();
// ... drawing operations ...
bitmap.Unlock();

// Set overlay
player.SetOverlay(bitmap);

// Remove overlay
player.RemoveOverlay();

Subtitles

Configure subtitle appearance using SubtitleDecoration:

player.SubtitleDecoration = new SubtitleDecoration
{
    FontFamily = "Segoe UI",
    FontSize = 24,
    Bold = true,
    BackgroundColor = "#80000000", // Semi-transparent black
};

Property	Type	Description
FontFamily	string	Font family name
FontSize	double	Font size in pixels
Bold	bool	Bold text
BackgroundColor	string	Background color in #ARGB format

Snapshots

Capture the current video frame as a JPEG image:

using var stream = await player.TakeSnapshot();
if (stream != null)
{
    // Save to file
    using var fileStream = File.Create("snapshot.jpg");
    await stream.CopyToAsync(fileStream);
}

VideoPreviewControl

The VideoPreviewControl provides a lightweight preview surface for video capture and mixing scenarios.

<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vast="clr-namespace:VAST.Controls;assembly=VAST.UI">
    <vast:VideoPreviewControl x:Name="preview"
                              RenderingStrategy="LowLatency"
                              RendererType="Best" />
</Window>

Property	Type	Default	Description
Renderer	IVideoRenderer	null	Active renderer instance (read-only)
RendererType	VideoRendererType	Best	Renderer selection
RenderingStrategy	RenderingStrategy	LowLatency	Rendering optimization mode

Connecting to a Capture Source

To display video from a capture device, assign the Renderer to the capture source's Renderer property.

// Configure rendering
preview.RenderingStrategy = RenderingStrategy.LowLatency;
preview.RendererType = VideoRendererType.Best;

// Connect the renderer to the capture source
videoCaptureSource.Renderer = preview.Renderer;

// ...

// Disconnect renderer to stop preview
videoCaptureSource.Renderer = null;

Rendering

Renderer Types

Type	Description
Auto	Automatically select the best available renderer (DirectX 11 preferred)
Best	Use hardware-accelerated DirectX 11 rendering
Compatible	Use CPU-based WriteableBitmap rendering (fallback when DirectX unavailable)

Rendering Strategies

Strategy	Description
LowLatency	Frames rendered immediately when decoded. Best for live streams and real-time monitoring.
Smooth	Frame timing based on timestamps. Best for VOD content and recorded media.

DirectX Renderer

The DirectX renderer uses HwndHost to embed a native DirectX 11 swap chain within the WPF visual tree:

• Creates a child window for DirectX rendering
• Integrates with WPF layout and transforms
• Hardware-accelerated video decoding and rendering

Compatible Renderer

The WriteableBitmap compatible renderer provides fallback rendering when DirectX is unavailable:

• Automatic color space conversion to BGRA
• Device offline image support (displays placeholder when capture device disconnects)
• Thread-safe bitmap updates via WPF Dispatcher

Troubleshooting

Common Issues

Issue	Cause	Solution
Black screen	Renderer not initialized	Ensure control is visible and has non-zero size
No DirectX rendering	DirectX 11 unavailable	Set VideoRendererType = Compatible to use WriteableBitmap fallback
Mouse gestures not working	PTZ disabled	Set PlaybackParameters.AllowDigitalPTZ = true
Poor performance	Software rendering active	Ensure DirectX 11 is available; update graphics drivers
Overlay not displaying	Wrong pixel format	Use PixelFormats.Pbgra32 or PixelFormats.Bgra32 for overlay bitmaps

Platform Notes

• DirectX 11 requires Windows 7 SP1 or later with Platform Update
• WriteableBitmap fallback works on all Windows versions
• Hardware acceleration depends on graphics driver support
• WASAPI audio output requires Windows Vista or later

See Also

• Supported Platforms - Platform compatibility matrix
• UI Libraries - Overview of all UI libraries
• VAST.Common Library - Core media types
• VAST.Common.Ext.Win32 Library - Windows platform extensions