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• ffmpeg black screen issue for video video generation from a list of frames

  11 mai 2023, par arlaine

  I used a video to generate a list of frames from it, then I wanted to create multiple videos from this list of frames.
I've set starting and ending frames indexes for each "sub video", so for example,
indexes = [[0, 64], [64, 110], [110, 234], [234, 449]], and those indexes will help my code generate 4 videos of various durations. The idea is to decompose the original video into multiple sub videos. My code is working just fine, the video generated.

  


  But every sub video start with multiple seconds of black screen, only the first generated video (so the one using indexes[0] for starting and ending frames) is generated without this black screen part. I've tried changing the frame rate for each sub_video, according to the number of frames and things like that, but I didn't work. You can find my code below

  


  for i, (start_idx, end_idx) in enumerate(self.video_frames_indexes):
    if end_idx - start_idx > 10:
        shape = cv2.imread(f'output/video_reconstitution/{video_name}/final/frame_{start_idx}.jpg').shape
        os.system(f'ffmpeg -r 30 -s {shape[0]}x{shape[1]} -i output/video_reconstitution/{video_name}/final/frame_%d.JPG'
              f' -vf "select=between(n\,{start_idx}\,{end_idx})" -vcodec libx264 -crf 25'
              f' output/video_reconstitution/IMG_7303/sub_videos/serrage_{i}.mp4')


  


  Just the ffmpeg command

  


  ffmpeg -r 30 -s {shape[0]}x{shape[1]} -i output/video_reconstitution/{video_name}/final/frame_%d.JPG -vf "select=between(n\,{start_idx}\,{end_idx})" -vcodec libx264 -crf 25 output/video_reconstitution/IMG_7303/sub_videos/serrage_{i}.mp4


  


• Xvfb records a black screen

  11 mai 2024, par Vivek

  I am trying a record a video by running xvfb inside a docker image. No matter what I do it gives me black screen.

  


  Screen size same in xvfb and ffmpeg and puppeteer.

  


  It will would really great if someone can help.

  


  
start-xvfb.sh
---------------------------------------------------------------------
# Start Xvfb
Xvfb :99 -screen 0 1280x720x24 &

# Set the display environment variable
export DISPLAY=:99

# Run the application (assuming it starts with npm start)
npm run dev


  


  Dockerfile

  


  FROM node:lts-alpine3.19

# Install dependencies using apk
RUN apk update && \
    apk add --no-cache \
    gnupg \
    ffmpeg \
    libx11 \
    libxcomposite \
    libxdamage \
    libxi \
    libxtst \
    nss \
    cups-libs \
    libxrandr \
    alsa-lib \
    pango \
    gtk+3.0 \
    xvfb \
    bash \
    curl \
    udev \
    ttf-freefont \
    chromium \
    chromium-chromedriver

# Set working directory
WORKDIR /app

# Copy package.json and install dependencies
COPY package.json .
RUN npm install --force

# Copy remaining source code
COPY . .

# Add a script to start Xvfb
COPY start-xvfb.sh /app/start-xvfb.sh
RUN chmod +x /app/start-xvfb.sh

# Expose the port
EXPOSE 4200
EXPOSE 3000

# Command to start Xvfb and run the application
CMD ["./start-xvfb.sh"]


  


  Below

  


  this is code code that launches puppeteer and from a nodejs application and create spawns a process for ffmpeg

  


  export class UnixBrowserRecorder implements Recorder {&#xA;&#xA;  url = &#x27;https://stackoverflow.com/questions/3143698/uncaught-syntaxerror-unexpected-token&#x27;; // Replace with your URL&#xA;  outputFilePath = `/app/output_video.mp4`; // Output file path within the container&#xA;  durationInSeconds = 6; // Duration of the video in seconds&#xA;  resolution = &#x27;1280x720&#x27;;&#xA;&#xA;  public async capture(): Promise<string> {&#xA;    const browser = await puppeteer.launch({&#xA;      args: [&#xA;        &#x27;--no-sandbox&#x27;, // Required in Docker&#xA;        &#x27;--disable-setuid-sandbox&#x27;, // Required in Docker&#xA;        &#x27;--disable-dev-shm-usage&#x27;, // Required in Docker&#xA;        &#x27;--headless&#x27;, // Run browser in headless mode&#xA;        &#x27;--disable-gpu&#x27;, // Disable GPU acceleration&#xA;        `--window-size=${this.resolution}` // Set window size&#xA;      ],&#xA;      executablePath: &#x27;/usr/bin/chromium&#x27; // Specify the path to Chromium executable&#xA;    });&#xA;&#xA;    const page = await browser.newPage();&#xA;    await page.goto(this.url);&#xA;&#xA;    await page.screenshot({&#xA;      "type": "png", // can also be "jpeg" or "webp" (recommended)&#xA;      "path": `/app/screenshot.png`,  // where to save it&#xA;      "fullPage": true,  // will scroll down to capture everything if true&#xA;    });&#xA;&#xA;    //ffmpeg -video_size `DISPLAY=:5 xdpyinfo | grep &#x27;dimensions:&#x27;|awk &#x27;{print $2}&#x27;` -framerate 30 -f x11grab -i :5.0&#x2B;0,0 output.mpg&#xA;&#xA;    const ffmpegProcess = spawn(&#x27;ffmpeg&#x27;, [&#xA;      &#x27;-video_size&#x27;, this.resolution,&#xA;      &#x27;-framerate&#x27;, &#x27;30&#x27;,&#xA;      &#x27;-f&#x27;, &#x27;x11grab&#x27;,&#xA;      &#x27;-i&#x27;, &#x27;:99&#x27;, // Use display :99 (assuming Xvfb is running on this display)&#xA;      &#x27;-t&#x27;, this.durationInSeconds.toString(),&#xA;      &#x27;-c:v&#x27;, &#x27;libx264&#x27;,&#xA;      &#x27;-loglevel&#x27;, &#x27;debug&#x27;,&#xA;      &#x27;-pix_fmt&#x27;, &#x27;yuv420p&#x27;,&#xA;      this.outputFilePath&#xA;    ]);&#xA;&#xA;    // Log ffmpeg output&#xA;    ffmpegProcess.stdout.on(&#x27;data&#x27;, data => {&#xA;      console.log(`ffmpegProcess stdout: ${data}`);&#xA;    });&#xA;&#xA;    ffmpegProcess.stderr.on(&#x27;data&#x27;, data => {&#xA;      console.error(`ffmpegProcess stderr: ${data}`);&#xA;    });&#xA;&#xA;    // Handle ffmpegProcess process exit&#xA;    ffmpegProcess.on(&#x27;close&#x27;, code => {&#xA;      console.log(`ffmpeg process exited with code ${code}`);&#xA;    });&#xA;&#xA;    // Wait for the duration to complete&#xA;    await new Promise(resolve => setTimeout(resolve, this.durationInSeconds * 1000));&#xA;&#xA;    // Close the FFmpeg stream and process&#xA;    ffmpegProcess.stdin.end();&#xA;    // Close Puppeteer&#xA;    await page.close();&#xA;    await browser.close();&#xA;&#xA;    return "Video generated successfully";&#xA;  }&#xA;}&#xA;</string>

  


  

  


• ffmpeg command produces black image as output

  3 mars 2020, par Nishad DESHMUKH

  Input #0, video4linux2,v4l2, from ’/dev/video0’ :

  Duration : N/A, start : 13555.753906, bitrate : 147456 kb/s

  Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 640x480, 147456 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc

  Stream mapping :

  Stream #0:0 -> #0:0 (rawvideo (native) -> mjpeg (native))

  Press [q] to stop, [?] for help
  [swscaler @ 0x55fd0eafa3e0] deprecated pixel format used, make sure you did set range correctly
  Output #0, image2, to ’test1.jpeg’ :

  Metadata :

  encoder         : Lavf57.83.100
  
  
  
  Stream #0:0: Video: mjpeg, yuvj422p(pc), 640x480, q=2-31, 200 kb/s, 30 fps, 30 tbn, 30 tbc
  
  
  
  Metadata:
  
  
  
    encoder         : Lavc57.107.100 mjpeg
  
  
  
  Side data:
  
  
  
    cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1

  frame= 1 fps=0.0 q=1.6 Lsize=N/A time=00:00:00.03 bitrate=N/A speed=8.41x

  video:3kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead : unknown