FFmpegBlazor (Blazor WASM)

FFmpegBlazor provides ability to utilize ffmpeg.wasm from Blazor Wasm C#.
ffmpeg.wasm is a pure Webassembly / Javascript port of FFmpeg. It enables video & audio record, convert and stream right inside browsers.
Supports Lazy loading of ffmpeg binary. It is self hosted version one time download of core ffmpeg wasm lib will be 25Mb.

Video Tutorial : Link Credit Dev Express

Installation

Download package via Nuget or DotNet CLI and you are good to go , no extra configuration required.

dotnet add package FFmpegBlazor 

API Documentation

Running WASM App

Running Locally

Currently we need to use a workaround to run FFmpegApps on web assembly, this will be removed in .NET 10 (Early September 2025) once Multi threading support is available on WASM, and these headers are injected.

We need to add 2 headers in Blazor WASM-local-server and in actual deployment static server also

Cross-Origin-Embedder-Policy: require-corp
Cross-Origin-Opener-Policy: same-origin

To do so we can create a web.config file in root of our project with content

<?xml version="1.0" encoding="utf-8"?>
<configuration>
	<system.webServer>
		<httpProtocol>
			<customHeaders>
				<add name="Cross-Origin-Embedder-Policy" value="require-corp"/>
				<add name="Cross-Origin-Opener-Policy" value="same-origin"/>
			</customHeaders>
		</httpProtocol>
	</system.webServer>

</configuration>

Use IIS Express to run apps locally. Also In actual deployment we need to add these 2 headers in server config to avoid SharedArrayBuffer not defined error. You can check Netlify deployment sample here.
Thanks to @aokocax for helping with it.

Running Published

Run following in published wwwroot folder with dotnet serve tool.

dotnet serve -p 8000 -h "Cross-Origin-Embedder-Policy: require-corp" -h "Cross-Origin-Opener-Policy: same-origin"

Sample

Here is a sample page to convert mp4 to mp3 and play it in browser.

@page "/"
@using FFmpegBlazor
@inject IJSRuntime Runtime
@using Microsoft.AspNetCore.Components.Forms


<InputFile OnChange="fileLoad" /><br /> <br />
<video width="300" height="200" autoplay controls src="@url" /><br /><br />
<button class="btn btn-primary" @onclick="Process">Convert Mp3</button><br /><br />
<audio controls src="@url2" />

@code
{
    string url; string url2;
    FFMPEG ff;
    byte[] buffer;

    protected override async Task OnInitializedAsync()
    {
        if (FFmpegFactory.Runtime == null)
        {
            FFmpegFactory.Logger += WriteLogs;
            FFmpegFactory.Progress += ProgressChange;
        }

        //initialize Library
        await FFmpegFactory.Init(Runtime);
    }

    async void fileLoad(InputFileChangeEventArgs v)
    {
        //get fist file from input selection
        var file = v.GetMultipleFiles()[0];

        //read all bytes
        using var stream = file.OpenReadStream(100000000); //Max size for file that can be read
        buffer = new byte[file.Size];

        //read all bytes
        await stream.ReadAsync(buffer);

        //create a video link from buffer so that video can be played
        url = FFmpegFactory.CreateURLFromBuffer(buffer, "myFile.mp4", file.ContentType);

        //reRender DOM
        StateHasChanged();
    }

    async void Process()
    {
        //create an instance
        ff = FFmpegFactory.CreateFFmpeg(new FFmpegConfig() { Log = true });

        //download all dependencies from cdn
        await ff.Load(); 

        if (!ff.IsLoaded) return;

        //write buffer to in-memory files (special emscripten files, Ffmpeg only interact with this file)
        ff.WriteFile("myFile.mp4", buffer);

        //Pass CLI argument here equivalent to ffmpeg -i myFile.mp4 output.mp3
        await ff.Run("-i", "myFile.mp4", "output.mp3");

        //delete in-memory file
        //ff.UnlinkFile("myFile.mp4");
    }

    async void ProgressChange(Progress m)
    {
         // display progress % (0-1)
        Console.WriteLine($"Progress {m.Ratio}");

        //if ffmpeg processing is complete (generate a media URL so that it can be played or alternatively download that file)
        if (m.Ratio == 1)
        {
            //get bytepointer from c wasm to c#
            var res = await ff.ReadFile("output.mp3");


            //generate a url from file bufferPointer
            url2 = FFmpegFactory.CreateURLFromBuffer(res, "output.mp3", "audio/mp3");

            //Download the file instantly

            //FFmpegFactory.DownloadBufferAsFile(res, "output.mp3", "audio/mp3");

            StateHasChanged();
        }
    }

    void WriteLogs(Logs m)
    {
        Console.WriteLine(m.Type + " " + m.Message);
    }
}