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• Revision 80a4f55989 : Enable background detection for adaptive quantizer control This commit enables

  17 avril 2014, par Jingning Han

  Changed Paths :
   Modify /vp9/encoder/vp9_aq_cyclicrefresh.c

  
   Modify /vp9/encoder/vp9_block.h

  
   Modify /vp9/encoder/vp9_encodeframe.c

  
  
  Enable background detection for adaptive quantizer control

  This commit enables a background detection approach for adaptive
  quantizer control. It combines the cyclic refresh pattern and the
  background information to determine the segment id for adaptive
  quantizer selection, prior to the non-RD mode decision process.
  It hence allows proper quantization information update for a more
  precise rate-distortion modeling in the non-RD mode decision.

  The compression performance of speed -5 for rtc set is improved
  by 2.5%, at no speed change.

  Change-Id : Ic3713e8ed9185b403b5b1679d19dabd57506d452

• Extract jpg images from mp4, crop and save exif

  5 juin 2017, par StevenH

  I am trying to take some dashcam footage, crop it, export 1fps to jpg and then the bit I’m stuck on add exif/file date to match the time & date it would have been taken based on my input video.

  The following command does the crop and export to jpg :

  ffmpeg -i c:\temp\dashcam\vid1.mp4 -vf "crop=2560:1311:0:0, fps=1" c:\temp\dashcam\vid1%03d.jpg

  Can I somehow do this by combining a command with ffprobe.

  Ideally I would also add gpx location data using a matching vid1.gpx but there are plenty of tools to do that bit if I can get jpgs with the correct date and time.

  Any help appreciated, thanks.

• .NET Process - Redirect stdin and stdout without causing deadlock

  21 juillet 2017, par user1150856

  I’m trying to encode a video file with FFmpeg from frames generated by my program and then redirect the output of FFmpeg back to my program to avoid having an intermediate video file.

  However, I’ve run into what seems to be a rather common problem when redirecting outputs in System.Diagnostic.Process, mentioned in the remarks of the documentation here, which is that it causes a deadlock if run synchronously.

  After tearing my hair out over this for a day, and trying several proposed solutions found online, I still cannot find a way to make it work. I get some data out, but the process always freezes before it finishes.

  ---

  Here is a code snippet that produces said problem :

  static void Main(string[] args)
  
      {
  
  
  
          Process proc = new Process();
  
  
  
          proc.StartInfo.FileName = @"ffmpeg.exe";
  
          proc.StartInfo.Arguments = String.Format("-f rawvideo -vcodec rawvideo -s {0}x{1} -pix_fmt rgb24 -r {2} -i - -an -codec:v libx264 -preset veryfast -f mp4 -movflags frag_keyframe+empty_moov -",
  
              16, 9, 30);
  
          proc.StartInfo.UseShellExecute = false;
  
          proc.StartInfo.RedirectStandardInput = true;
  
          proc.StartInfo.RedirectStandardOutput = true;
  
  
  
          FileStream fs = new FileStream(@"out.mp4", FileMode.Create, FileAccess.Write);
  
  
  
          //read output asynchronously
  
          using (AutoResetEvent outputWaitHandle = new AutoResetEvent(false))
  
          {
  
              proc.OutputDataReceived += (sender, e) =>
  
              {
  
                  if (e.Data == null)
  
                  {
  
                      outputWaitHandle.Set();
  
                  }
  
                  else
  
                  {
  
                      string str = e.Data;
  
                      byte[] bytes = new byte[str.Length * sizeof(char)];
  
                      System.Buffer.BlockCopy(str.ToCharArray(), 0, bytes, 0, bytes.Length);
  
                      fs.Write(bytes, 0, bytes.Length);
  
                  }
  
              };
  
          }
  
  
  
  
  
          proc.Start();
  
          proc.BeginOutputReadLine();
  
  
  
          //Generate frames and write to stdin
  
          for (int i = 0; i < 30*60*60; i++)
  
          {
  
              byte[] myArray = Enumerable.Repeat((byte)Math.Min(i,255), 9*16*3).ToArray();
  
              proc.StandardInput.BaseStream.Write(myArray, 0, myArray.Length);
  
          }
  
  
  
          proc.WaitForExit();
  
          fs.Close();
  
          Console.WriteLine("Done!");
  
          Console.ReadKey();
  
  
  
      }

  Currently i’m trying to write the output to a file anyway for debugging purposes, but this is not how the data will eventually be used.

  If anyone knows a solution it would be very much appreciated.