MediaRecorder

@inject Bit.Butil.MediaRecorder recorder

var supported = await recorder.IsSupported();
var webm = await recorder.IsTypeSupported("video/webm;codecs=vp9,opus");

// MediaRecorder.CommonVideoTypes / CommonAudioTypes are ready-made candidate lists:
var available = await recorder.GetSupportedTypes(MediaRecorder.CommonVideoTypes);
var best = available.FirstOrDefault();

private MediaStreamHandle? _stream;
private MediaRecordingHandle? _recording;
private string? _playbackUrl;

// 1. open a stream, 2. record it
_stream = await mediaDevices.GetUserMedia(audio: true, video: true);
_recording = await recorder.Start(_stream!, new MediaRecorderOptions
{
    MimeType = (await recorder.GetSupportedTypes()).FirstOrDefault(),
});

// later - the blob stays in the browser, only the URL crosses:
var media = await _recording!.StopAndCreateObjectUrl();
_playbackUrl = media?.ObjectUrl;   // <video src="@_playbackUrl" controls />

// or pull the bytes into C# to upload or save:
// var media = await _recording.Stop();
// await File.WriteAllBytesAsync(path, media!.Data!);

// release the blob when you're done with it (the service, not the handle - stopping
// the recording already retired the handle):
await recorder.RevokeObjectUrl(_playbackUrl);

@inject Bit.Butil.MediaRecorder recorder

@code {
    private long _bytesSoFar;
    private MediaStreamHandle? _stream;        // from mediaDevices.GetUserMedia
    private MediaRecordingHandle? _recording;

    private async Task Start()
    {
        _recording = await recorder.Start(
            _stream!,
            onData: chunk => InvokeAsync(() =>
            {
                _bytesSoFar += chunk.Length;   // upload it, append it to a file, ...
                StateHasChanged();
            }),
            timesliceMs: 1000);   // one slice per second
    }

    // flush early, without stopping:
    private async Task Flush() => await _recording!.RequestData();
}