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• After video codec copy to mp4 format with ffmpeg,new video has no screen and has just audio

  19 juin 2018, par parsa

  I have an issue.sometimes when I convert video to mp4 with codec copy,my created video in chrome just has audio and it’s display a black screen, and in another browsers like firefox and internet explorer video doesn’t play.
  but I check this created video on my server and video displays.
  And here is my code in below

  ffmpeg -i -f mp4 -s 123.mov -codec copy 123.mp4 

  The Output Of ffprobe 123.mp4 is :

  Metadata:major_brand:isom
  
  minor_version :512
  
  compatible_brands:isomiso2mp41
  
  encoder:Lavf57.31.100
  
  Duration: 00:26:58.97, start: 0.000000, bitrate: 1334 kb/s
  
  Stream #0:0(und): Video: mpeg4 (Advanced Simple Profile) (mp4v / 0x7634706D)
  
  ,yuv420p, 640x480 [SAR 1:1 DAR 4:3],1200 kb/s, 29.97 fps,29.97 tbr, 30k tbn,29.97 tbc (default)
  
  Metadata:handler_name: VideoHandler
  
  Stream #0:1(und): Audio: mp3 (mp4a / 0x6134706D), 44100 Hz, stereo, s16p, 12
  
  7 kb/s (default)
  
  Metadata:handler_name: SoundHandler

• Aforge.NET Video Size Decreases When Writing Back Frames to the Video

  23 août 2016, par Irfan Babar

               try { VideoFileReader reader = new VideoFileReader();
  
                 VideoFileWriter wrt = new VideoFileWriter();
  
                 tot = reader.FrameCount;
  
                  wrt.Open("outvid.mp4",reader.Width,reader.Height,reader.FrameRate,VideoCodec.MPEG4);
  
                  Bitmap videoFrame = null;
  
  
  
                  for (int i = 1; i <= tot; i++)
  
                  {
  
                       videoFrame = reader.ReadVideoFrame();
  
  
  
                       wrt.WriteVideoFrame(videoFrame );
  
                       videoFrame .Dispose();
  
                  }
  
                  wrt.Close();
  
                  reader.Close();
  
  
  
  
  
              }
  
          }
  
          catch (Exception exc)
  
          {
  
              MessageBox.Show( exc.ToString());
  
          }

  after writing back the video size and resolution also decrease, what shoud i do to make perfect frame writing back into the video ?
  Actually I am reading frame by frame from one video and writing that video frame in another video without any modification,Please suggest me solutions

• FFMPEG scaling video disable viewing it while process is not ended, for video transcoding on the fly

  5 juillet 2022, par Lucas F

  Good day all,

  


  I'm working on a video player with 1080p original video files, and I would like to change their resolution on the fly :

  


  Actually I host all my original video files under a web mp4 1080p format, and I would like to be able to offer 720p, 480p, etc ... qualities.

  


  So I started to look for tutorials about video transcoding on the fly and I found the FFMPEG tool.

  


  I'm actually using the following command to scale videos - to 720p for e.g. :

  


  ffmpeg -i input.mp4 -vf scale=-1:720 output.mp4


  


  The problem is, once FFMPEG starts scaling it, I have to wait the end of the process before being able to play the video. Do you know if there is any parameter for this command to allow playing the video while it's under scaling ?

  


  Or any workaround that can help me doing this ?

  


  Thank you in advance for your help !

  


  EDIT

  


  Now I found how to access readable content while transcoding (by transcoding to fragmented MP4) :

  


  ffmpeg -i input.mp4 -vf scale=-2:720 -movflags +frag_keyframe+separate_moof+omit_tfhd_offset+empty_moov output.mp4


  


  But my problem is when opening the video it comes as an "ended" video of the current transcoded data.

  


  So if video lasts 1min and is half transcoded, I'll see only 30s, it will not load more data, once the rest is transcoded.