Overlay Image On Video#

How to overlay PNG image on top of MP4 video.

Source Video#

For a source video we use the MP4 file from the TED talk video What’s the next window into our universe? by Andrew Connolly. The original video format is Wide 480p or 16:9, 854 x 480.

Overlay Image#

For overlay image we use iFunnyIcon, but you can use any other image instead. Just make sure the image width and height are of even size, i.e. a multiple of 2. That is a requirement of the AVBlocks overlay filter.

Complete Program#

This code overlays a PNG image on top of a MP4 video.

using PrimoSoftware.AVBlocks;
using System.Collections.Generic;

namespace OverlayImage
    class Program
        static void Main(string[] args)

            // start with two identical input and output configurations
            var inputInfo = new MediaInfo() {
                InputFile = "AndrewConnolly_2014.mp4"

            var outputInfo = new MediaInfo() {
                InputFile = "AndrewConnolly_2014.mp4"

            var imageInfo = new MediaInfo() {
                InputFile = "Icon.png"

            if (inputInfo.Load() && outputInfo.Load() && imageInfo.Load()) {
                // create input socket
                var inputSocket = MediaSocket.FromMediaInfo(inputInfo);

                // create output socket
                var outputSocket = MediaSocket.FromMediaInfo(outputInfo);
                outputSocket.File = "AndrewConnolly_2014_With_Overlay.mp4";

                // read overlay image
                var imageData = System.IO.File.ReadAllBytes(imageInfo.InputFile);
                var imageBuffer = new MediaBuffer(imageData);
                var imageFormat = imageInfo.Streams[0] as VideoStreamInfo;

                // set overlay parameters
                var outVideoPin = outputSocket.Pins[0];
                outVideoPin.Params = new Dictionary<string, object>() {
                    // overlay parameters

                    // Compositing mode and alpha
                    // see https://en.wikipedia.org/wiki/Alpha_compositing
                    { Param.Video.Overlay.Mode, AlphaCompositingMode.Over },
                    { Param.Video.Overlay.BackgroundAlpha, 1.0 },
                    { Param.Video.Overlay.ForegroundAlpha, 0.2 },

                    // position at the top left corner
                    { Param.Video.Overlay.BackgroundX, 0 },
                    { Param.Video.Overlay.BackgroundY, 0 },

                    // provide the actual image data
                    { Param.Video.Overlay.ForegroundBuffer, imageBuffer },
                    { Param.Video.Overlay.ForegroundBufferFormat, imageFormat},

                    // force video decoding and encoding. Otherwise 
                    // video is transferred as is, and the overlay 
                    // filter is not applied.
                    { Param.ReEncode, Use.On },

                    // enable hardware accelerated encoding (optional)
                    { Param.HardwareEncoder, HardwareEncoder.Auto }

                // create a transcoder and run it
                using (var transcoder = new Transcoder()) {
                    // set inputs and outputs

                    // process
                    if (transcoder.Open())


How to run#

Follow the steps to create a C# console application in Visual Studio but in Program.cs use the code from this article.

Download the AndrewConnolly_2014.mp4 MPEG4 file from the Internet Archive and save it in bin/x64/Debug/net6.0 under the project’s directory.

Download the Icon.png image file from the Internet Archive and save it in bin/x64/Debug/net6.0 under the project’s directory.

Run the application in Visual Studio. Wait a few seconds for the Transcoder to finish. The converted file AndrewConnolly_2014_With_Overlay.mp4 will be in the bin/x64/Debug/net6.0 directory.