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• Overlaying one video on another one, and making black pixels transparent

  25 janvier 2023, par Michael A

  I'm trying to use FFMPEG to create a video with one video overlayed on top another.

  



  I have 2 MP4s. I need to make all BLACK pixels in the overlay video transparent so that I can see the main video underneath it.

  



  I found two ways to overlay one video on another :

  



  First, the following positions the overlay in the center, and therefore, hides that portion of the main video beneath it :

  



      ffmpeg -i 1.mp4 -vf "movie=2.mp4 [a]; [in][a] overlay=352:0 [b]" combined.mp4 -y


  



  And, this one, places the overlay video on the left, but it's opacity is set to 50% so at least other one beneath it is visible :

  



  ffmpeg -i 1.mp4 -i 2.mp4 -filter_complex "[0:v]setpts=PTS-STARTPTS[top]; [1:v]setpts=PTS-STARTPTS, format=yuva420p,colorchannelmixer=aa=0.5[bottom]; [top][bottom]overlay=shortest=0" -acodec libvo_aacenc -vcodec libx264 out.mp4 -y


  



  My goal is simply to make all black pixels in the overlay (2.mp4) completely transparent. How can this be done.

  


• Black detect ffmpeg and use in a javascript

  6 février 2023, par sol

  I had an ffmpeg script that allow me to detect black frames from a video file sample from the bottom.

  


  and i want to create a javascript code that will allow me to do the same function sample from the bottom but its not working.

  


  original code from ffmpeg script :

  


  `ffmpeg -i LKE-BLACK.mp4 -vf "blackdetect=d=0.5:pix_th=0.10" -an -f null - 2>&1 | findstr blackdetect > output.txt

  


  node script :

  


  var fs = require('fs');
const ffmpeg = require("ffmpeg.js");

var createStream = fs.createWriteStream("data.txt");
createStream.end();

const transcode = async ({ target: { files }  }) => {
    message.innerHTML = 'Loading ffmpeg-core.js';
    await ffmpeg.load();
    message.innerHTML = 'Start transcoding';
    
    await ffmpeg.transcode('-i', 'LKE-BLACK.mp4', "-vf", "blackdetect=d=0.5:pix_th=0.10", '-an', '-f', 'null - 2>&1', );
    message.innerHTML = 'Complete transcoding';

    fs.writeFile("data.txt", function (err) {
        if (err) throw err;
        console.log('File is created successfully.');
      });
}


  


• Black video when using ffplay of received data over upd [closed]

  4 février 2023, par Alexandru-Marian Buza

  I'm encoding frames from a id3d11texture2d, and the receive packet size is around 70-80.
When i'm sending over udp, and use ffplay to show the video, i get a black screen.
Resolution and fps are well determined by ffplay.

  


  AcquiredBuffer.Attach(Buffer.MetaData.pSurface);

            ID3D11Texture2D* texture;
            ID3D11Texture2D* stagingTexture;
            AcquiredBuffer->QueryInterface(IID_PPV_ARGS(&texture));
            
            texture->GetDesc(&desc);
            desc.Usage = D3D11_USAGE_STAGING;
            desc.CPUAccessFlags = D3D11_CPU_ACCESS_READ;
            desc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
            desc.BindFlags = 0;
            desc.MiscFlags = 0;
            hr = m_Device->Device->CreateTexture2D(&desc, NULL, &stagingTexture);
            if (stagingTexture != 0) {
                m_Device->DeviceContext->CopyResource(stagingTexture, texture);
                D3D11_MAPPED_SUBRESOURCE mappedData;
                m_Device->DeviceContext->Map(stagingTexture, 0, D3D11_MAP_READ, 0, &mappedData);
                
                memcpy(frame->data[0], mappedData.pData, mappedData.DepthPitch);
                auto ret = avcodec_send_frame(codec, frame);
                if (ret < 0) {
                    writeText("Send frame failed");
                }
                else {
                    while (ret >= 0) {
                        ret = avcodec_receive_packet(codec, packet);
                        for (int i = 0; i < packet->size; i++) {
                            if (packet->data[i] != 0) {
                            }
                        }
                        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
                            break;
                        }
                        else if (ret < 0) {
                            writeText("Error durring encoding");
                        }
                        if (sendto(s, (char*)packet->data, packet->size * sizeof(uint8_t), 0, (sockaddr*)&dest, sizeof(dest)) == SOCKET_ERROR) {
                            writeText("Failed to send frame");
                        }
                        av_packet_unref(packet);
                    }
                }
                
                m_Device->DeviceContext->Unmap(stagingTexture, 0);
                stagingTexture->Release();