About

Blazor components for capturing and playing media in the browser: camera photo and video capture with live preview (getUserMedia + MediaRecorder APIs), microphone audio recording with live input level metering, a simple HTML file capture input (native camera app on mobile devices), video/audio player components fully controllable from .NET code and a live audio visualizer (FFT frequency spectrum / waveform) for recorders and players. All components work with WebAssembly and Server hosted models. For code examples see usage.

You can try it out by using the demo app.

Note: camera and microphone access requires a secure context (HTTPS or localhost) and is granted by the user per site.

Components and services

Capture

• CameraCapture: renders an HTML <video> element with live camera preview (getUserMedia). Take photos from the live stream in full camera resolution (TakePhotoAsync, returns a Blob URL to show and GetPhotoStreamAsync for the bytes) and record video with optional audio using the MediaRecorder API (StartRecordingAsync, PauseRecordingAsync, ResumeRecordingAsync, StopRecordingAsync). Camera can be selected by device Id or facing mode (front/rear). Preview Width/Height can be given in px or % (IsCameraDimensionInPixels).
• AudioRecorder: records audio from a microphone with the MediaRecorder API. Renders no HTML, use it with @ref from code: OpenMicrophoneAsync then StartRecordingAsync. Provides a live input level meter (OnAudioLevelChanged, RMS level 0..1) e.g. for volume bars.
• MediaFileCapture: the simple HTML way, no JS interop: renders <input type="file"> with accept and capture attributes. Mobile browsers open the native camera/recorder app, desktop browsers a file picker. Captured media arrives as IBrowserFile (OnFilesCaptured event).

Recordings are kept in the browser as a Blob: the reported MediaRecordingInfo contains a Blob URL which can be played back directly by the player components, and the raw bytes can be downloaded to .NET with GetRecordingStreamAsync() (e.g. to upload or save the recording).

Playback

• VideoPlayer: renders an HTML <video> element with playback events (OnPlay, OnPause, OnEnded, OnTimeUpdate, OnMetadataLoaded, OnError, ...) and control API (PlayAsync, PauseAsync, SeekAsync, SetVolumeAsync, SetMutedAsync, SetPlaybackRateAsync, GetStateAsync), plus RequestFullscreenAsync, TogglePictureInPictureAsync and CaptureFrameAsync (current frame as image). Width/Height can be given in px or % (IsPlayerDimensionInPixels).
• AudioPlayer: the same for an HTML <audio> element.

Player sources: regular URL (Source parameter or SetSourceAsync(url)), Blob URL of a recording (MediaRecordingInfo.Url) or .NET stream (SetSourceAsync(stream, mimeType) e.g. media from a database).

Visualization

• AudioVisualizer: renders a live audio visualization onto an HTML <canvas> using the Web Audio AnalyserNode API. Two modes: FFT frequency spectrum bars (spectrum analyzer) and time domain waveform (oscilloscope). Attach it to a capture component (CaptureSource, e.g. AudioRecorder microphone input) or to a player component (PlayerSource, e.g. AudioPlayer playback). Drawing runs entirely in JS with requestAnimationFrame (60 fps, no interop traffic); the FFT reduced to configurable bands (0..1 values) can additionally be reported to .NET via OnSpectrumChanged on a throttled timer for custom rendering. Configurable: FftSize, SmoothingTimeConstant, MinDecibels/MaxDecibels, BarCount, logarithmic/linear frequency scale, colors with optional gradient. Width/Height can be given in px or % (IsVisualizerDimensionInPixels), the drawing resolution follows the CSS size automatically. Note: cross-origin player sources need CORS headers, Blob URL recordings and .NET stream sources always work.

Services

• IMediaDeviceService: injectable service to list available cameras, microphones and speakers (GetMediaDevicesAsync), request media permissions (RequestPermissionsAsync), check getUserMedia/MediaRecorder browser support and list the supported recording MIME types (GetSupportedMimeTypesAsync).

Setup

Install the Majorsoft.Blazor.Components.Media NuGet package:

dotnet add package Majorsoft.Blazor.Components.Media

Register the services (only required for IMediaDeviceService):

using Majorsoft.Blazor.Components.Media;
...
builder.Services.AddMediaComponents();

Add the following usings to your components or _Imports.razor:

@using Majorsoft.Blazor.Components.Media
@using Majorsoft.Blazor.Components.Media.Capture
@using Majorsoft.Blazor.Components.Media.Players
@using Majorsoft.Blazor.Components.Media.Visualization

Usage

Camera photo and video capture

<CameraCapture @ref="_camera" Width="640" Height="480" RecordAudio="true"
			   OnPhotoTaken="PhotoTaken" OnRecordingFinished="RecordingFinished" OnCaptureError="CaptureError" />

<button @onclick="() => _camera.StartCameraAsync()">Start camera</button>
<button @onclick="() => _camera.TakePhotoAsync()">Take photo</button>
<button @onclick="() => _camera.StartRecordingAsync()">Record</button>
<button @onclick="() => _camera.StopRecordingAsync()">Stop</button>

@if (_photo is not null)
{
	<img src="@_photo.Url" width="320" />
}

<VideoPlayer @ref="_player" Width="640" Height="360" />

@code {
	private CameraCapture _camera;
	private VideoPlayer _player;
	private MediaPhotoInfo _photo;

	private void PhotoTaken(MediaPhotoInfo photo) => _photo = photo; //bytes: await _camera.GetPhotoStreamAsync()

	private async Task RecordingFinished(MediaRecordingInfo recording)
	{
		await _player.SetSourceAsync(recording.Url); //play back the recording from Blob URL
		//or download the bytes: await using var stream = await _camera.GetRecordingStreamAsync();
	}

	private void CaptureError(string error) { }
}

Microphone recording with level meter

<AudioRecorder @ref="_recorder" OnAudioLevelChanged="level => _level = level"
			   OnRecordingFinished="RecordingFinished" OnCaptureError="CaptureError" />

<button @onclick="() => _recorder.OpenMicrophoneAsync()">Open microphone</button>
<button @onclick="() => _recorder.StartRecordingAsync()">Record</button>
<button @onclick="() => _recorder.StopRecordingAsync()">Stop</button>

<progress max="1" value="@_level"></progress>

<AudioPlayer @ref="_audioPlayer" />

@code {
	private AudioRecorder _recorder;
	private AudioPlayer _audioPlayer;
	private double _level;

	private async Task RecordingFinished(MediaRecordingInfo recording)
		=> await _audioPlayer.SetSourceAsync(recording.Url);

	private void CaptureError(string error) { }
}

Voice recorder with FFT spectrum analyzer

AudioVisualizer starts automatically when the attached source becomes active (AutoStart, default true).

<AudioRecorder @ref="_recorder" OnRecordingFinished="RecordingFinished" OnCaptureError="CaptureError" />
<AudioVisualizer CaptureSource="_recorder" Width="640" Height="120"
				 BarColor="#2196f3" BarGradientColor="#f321a7" BarCount="48" />

<button @onclick="() => _recorder.OpenMicrophoneAsync()">Open microphone</button>
<button @onclick="() => _recorder.StartRecordingAsync()">Record</button>
<button @onclick="() => _recorder.StopRecordingAsync()">Stop</button>

@code {
	private AudioRecorder _recorder;

	private async Task RecordingFinished(MediaRecordingInfo recording) { /* play or upload it */ }
	private void CaptureError(string error) { }
}

The same for playback, e.g. a player showing the spectrum of the played audio (works with recordings, .NET stream sources and same-origin/CORS enabled URLs):

<AudioPlayer @ref="_player" Source="music.mp3" />
<AudioVisualizer PlayerSource="_player" Mode="AudioVisualizerModes.FrequencyBars" />

Waveform (oscilloscope) mode and .NET side FFT band data for custom rendering:

<AudioVisualizer CaptureSource="_recorder" Mode="AudioVisualizerModes.Waveform"
				 OnSpectrumChanged="bands => _bands = bands" SpectrumBandCount="16" SpectrumIntervalMs="100" />

@code {
	private double[] _bands; //16 values 0..1, e.g. for custom bars/LED meters
}

Simple HTML capture

<MediaFileCapture MediaType="CaptureMediaTypes.Photo" CaptureMode="CameraFacingModes.Environment"
				  OnFilesCaptured="FilesCaptured" />

@code {
	private async Task FilesCaptured(IReadOnlyList<IBrowserFile> files)
	{
		await using var stream = files[0].OpenReadStream(maxAllowedSize: 50 * 1024 * 1024);
		//process the captured photo/video/audio file
	}
}

Device enumeration

@inject IMediaDeviceService _mediaDeviceService

@code {
	protected override async Task OnAfterRenderAsync(bool firstRender)
	{
		if (firstRender)
		{
			//Permission needed to see device labels.
			var error = await _mediaDeviceService.RequestPermissionsAsync(audio: true, video: true);
			var devices = await _mediaDeviceService.GetMediaDevicesAsync();
			var cameras = devices.Where(d => d.IsVideoInput);
		}
	}
}