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• getting black screen while trying to record dockerized lxde using ffmpeg

  16 mars 2023, par Itzik.B

  I have created a docker image that has LXDE and TightVNCServer.

  


  # Pull base image.
FROM ubuntu

# Install LXDE and VNC server.
RUN apt-get update
RUN apt-get install -y xvfb
RUN DEBIAN_FRONTEND=noninteractive apt-get install -y lxde-core lxterminal tightvncserver
RUN rm -rf /var/lib/apt/lists/*
RUN touch /root/.Xresources
RUN touch /root/.Xauthority
COPY xstartup /root/.vnc/xstartup
RUN chmod +x /root/.vnc/xstartup
#Install Node.js & npm

# Define working directory.
WORKDIR /data

COPY * /data

RUN apt-get install -y ffmpeg


  


  I am running this container using this command :

  


  docker run -it --rm -v /data:/data -p 5901:5901 -e USER=root ubuntudsktp  bash -c "vncserver :1 -geometry 1280x800 -depth 24 && tail -F /root/.vnc/*.log"

  


  I am logging into this container using VNC and running this command to record the whole screen :

  


  ffmpeg -f x11grab -i :1.0 output.webm

  


  After the recording was over, I opened the video and I could see that the video is completely blank(black screen).

  


  I know there is a "screen" that I need to tell ffmpeg to record but its works only on -i :1.0.

  


  I have also tried to run it using :

  


  DISPLAY=:1 ffmpeg -f x11grab -i :1.0 output.webm
And the results are the same.

  


  What I am missing here ?

  


• FFMPEG overlay video with black background over an image not working without any errors

  19 juin 2018, par bil80

  I have a snow effect video with black background snow.mp4, and i want to overlay it over a fixed jpeg image.jpg
  The generated output video result was only with the image without the snow effect, my ffmpeg version is : 3.2.10, i don’t understand why it is not working with me, have you an idea ?

  This is my command line :

  ffmpeg -i image.jpg -i snow.mp4 -filter_complex '[1:v]scale=1280x768,setdar=16:9,colorkey=0x000000:0.3:0.2[ckout];[0:v]scale=1280x768,setdar=16:9,[ckout]overlay[out]' -map '[out]' output.mp4

  I tried also with the chromakey instead of colorkey, without success :/

  This is the result video that i got :
  output.mp4

  What i want is this result with snow effect : output_with_snow_effect.mp4

• JavaCV - strange black screen when playing a file with FFmpegFrameGrabber

  17 mai 2012, par noncom

  I am using JavaCV and it's FFmpegFrameGrabber in my project. It loads and player files OK, when I launch the project from Eclipse, but shows either a black screen or a still 1st frame when I run a compiled project. Sometimes comming with this error :

  Input #0, avi, from 'C:/path/Start_Cut.avi':
  
  Duration: 00:00:20.03, start: 0.000000, bitrate: 26002 kb/s
  
  Stream #0.0: Video: mpeg4, yuv420p, 1920x1080, 30 tbr, 30 tbn, 30 tbc
  
  Cannot allocate memory. com.googlecode.javacv.FrameGrabber$Exception: Cannot initialize the conversion c ontext.
  
              at com.googlecode.javacv.FFmpegFrameGrabber.start(FFmpegFrameGrabber.jav a:280)

  and sometimes with

  [mpeg4 @ 6A95DF20] Invalid and inefficient vfw-avi packed B frames detected
  
  Input #0, avi, from 'C:/path/Start_Cut.avi':
  
    Duration: 00:00:20.03, start: 0.000000, bitrate: 26002 kb/s
  
      Stream #0.0: Video: mpeg4, yuv420p, 1920x1080 [PAR 1:1 DAR 16:9], 25 tbr, 30
  
   tbn, 25 tbc

  does anyone has a clue on this ?

  UPDATE :

  I have been able to narrow down the problem. For some reason, FFmpegFrameGrabber returns null upn calling the grab() method. Why does it work in Eclipse and does not work in standalone build ? All libraries are included and I suppose, it would come up with an error if they did not.