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• ffmediaplayer playing but screen keeps black

  27 août 2023, par Joergahmann

  I#m coding a video tool for sports with the Windows Template Studio and using the Community Toolkit.MVVM. I finished this with the vlcMediaPlayer and it worked almost fine. I need the Frameback (vlc does not provide) and I like autohiding the controls (which is hard with vlc). So I decided to use the ffmediaelemrnt instead.
Almost everything is ok (I hear sound, i can pause, forward ..), only the Video is not showing !!

  


  I'm using an observable property

  


  `    [ObservableProperty]
     private MediaElement _ffmeMediaElement;`


  


  instead of the original implementation with a complete different basemodel :

  


  public MediaElement MediaElement
        {
            get
            {
                if (m_MediaElement == null)
                    m_MediaElement = (Application.Current.MainWindow as MainWindow)?.Media;

                return m_MediaElement;
            }
        }


  


  —> Could this be the problem ? How do I get the (Application.Current.MainWindow as MainWindow) ? in my case with no mainwindow and a page instead


  


                      



  


  What I tried
When I use a contentcontrol instead : the Video is showing, but the controls are not autohiding anymore

  


  When I compile your WindowsSample, it works completly, but still shows the error Object reference not set to an instance of an object on

  


  I would appreciate any help. Thank you in advance

  


• FFMPEG h.264 stream to VLC from raw YUV444 produces black screen

  30 novembre 2018, par GerbGerb

  Not sure if this fits better here or over on Super User, so please redirect if here is the wrong place.

  I am piping raw YUV444 640x480 frames to ffmpeg from inside a C++ program using stdout. ffmpeg encodes them using h.264 and streams the video via UDP to an IP of my choice.

  When I am not streaming and saving the video as -mp4 file, everything works - But when I stream over the network and try to receive in VLC, the stream is received and the playing timer under the video screen runs, but the image is black, none of the video is displayed. Also I have some crackling sounds on my audio output.

  My FFMPEG settings are as follows :

  ffmpeg -y -loglevel info -f rawvideo -r 25 -c:v rawvideo -pix_fmt yuv444p -s 640x480 -i - -c:v libx264 -preset superfast -framerate 25 -f mpegts udp://192.168.150.1:20001

  in VLC, I just use "open network stream" with udp ://@:20001. The port is open, I tested it with a simple dummy sender/receiver.
  Almost the same cli arguments for the video recording lead to a perfectly playable video when writing to a file and downloading it :

  ffmpeg -y -loglevel info -f rawvideo -r 25 -c:v rawvideo -pix_fmt yuv444p -s 640x480 -i - -c:v libx264 -preset superfast -framerate 25 video.mp4

  If I try to stream the same video using

  ffmpeg -i video.mp4 -v 0 -vcodec mpeg4 -f mpegts udp://192.168.150:20001

  the screen remains black.

  VLC debug output changes between different runs, because other modules are selected, so I assume stream type recognition goes haywire. But why ?

  What am I doing wrong ?

  Here the ffmpeg log
  and the VLC log

• How to automatically remove black bars using ffmpeg from a Powershell script ?

  27 avril 2021, par timlwsk

  Thanks to the help of the user mklement0 I got this script to automatically convert all files in the folder "video_old" and move them into "video_new", all while keeping the original filename. Original Post.

  



  Now I want to remove the black bars in the container. I know that there is "cropdetect" but AFAIK you have to manually parse the the value into the script. What parameter should I add to bellow's ffmpeg execution ?

  



  Get-ChildItem .\video_old -Filter *.mkv | ForEach-Object {
  .\ffmpeg.exe -i $_.FullName -c:v libx265 -crf 18 ".\video_new\$($_.Name)"
}


  



  Parameters used to remove the bars

  



  ffmpeg -ss 90 -i input.mkv -vframes 10 -vf cropdetect -f null -
...
[Parsed_cropdetect_0 @ 0x220cdc0] x1:0 x2:1279 y1:0 y2:719 w:1280 h:720 x:0 y:0 pts:215 t:0.215000 crop=1280:720:0:0
[Parsed_cropdetect_0 @ 0x220cdc0] x1:0 x2:1279 y1:0 y2:719 w:1280 h:720 x:0 y:0 pts:257 t:0.257000 crop=1280:720:0:0
[Parsed_cropdetect_0 @ 0x220cdc0] x1:0 x2:1279 y1:0 y2:719 w:1280 h:720 x:0 y:0 pts:299 t:0.299000 crop=1280:720:0:0


  



  In this example, we can apply the filter like this :

  



  ffmpeg -i input.mkv -vf crop=1280:720:0:0 -c:a copy output.mkv


  



  OriginalPost

  



  Screenshot