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• MP4 to all mobile compatible 3gp

  2 mai 2013, par Susheel Mishra

  I am using FFMPEG for converting mp4 video to 3gp.I want to convert it to low end android phone as well as iphone.I am not concern with quality.Using it on linux server with php.

  I searched but my need is diferent , hence post question.

  thanks

• Does Apple AS assembler replace certain NEON instructions with equivalent ones on iOS ?

  5 avril 2012, par Yi Wang

  I was trying to use ffmpeg on iOS and was debugging a crash in the optimized arm code. I have discovered that some unsigned (.u16, .u32) instruction have been replaced by signed ones (.i16, .i32). It's easy to see because disassembled instruction on GDB doesn't quite match the source code.

  For example,

  vrshrn.u32 -> vrshrn.i32
  
  vrshrn.u16 -> vrshrn.i16
  
  vadd.u16 -> vadd.i16

  My questions :

  1. Is this behavior correct and expected ? If not, how do we correct it ?
  2. If they are equivalent, why do we nee need the unsigned ones at all ? Is it because that way the code is more explicit ?
  3. Is this behavior expected with other platform's toolkit ? For example, Android's toolkit ? (I have heard Apple's AS is an ancient one)

• Redirect ffmpeg stdout to memorystream and convert it to image c#

  2 février 2016, par Zed Machine

  I want to get an image from ffmpeg stdout without saving it to disk.

  here is the code :

       public void GetFrame(string video, long millisectoseek)
  
      {
  
          panel1.BackgroundImage = null;
  
          this.Update();
  
  
  
          Process process = new Process();
  
  
  
          long seconds = millisectoseek / 1000;
  
          long millisec = millisectoseek % 1000;
  
  
  
          var cmd = String.Format(" -ss {0}.{1} -i \"{2}\" -vframes 1 -an -f image2pipe pipe:1", seconds, millisec.ToString("000"), video);
  
  
  
          process.StartInfo.RedirectStandardOutput = true;
  
          process.StartInfo.UseShellExecute = false;
  
          process.StartInfo.CreateNoWindow = true;
  
          process.StartInfo.FileName = "\"" + Application.StartupPath + "\\ffmpeg.exe\"";
  
          process.StartInfo.Arguments = cmd;
  
  
  
          process.Start();
  
          process.WaitForExit(100);
  
  
  
          try
  
          {
  
             Bitmap myimg = (Bitmap)Image.FromStream(process.StandardOutput.BaseStream);
  
  
  
              panel1.BackgroundImage = myimg;
  
  
  
              this.Update();
  
          }
  
          catch (Exception ex) {
  
              MessageBox.Show(ex.Message);
  
          }
  
      }

  The problem is that I get an ArgumentException (Parameters is not valid.) in Image.FromStream().. what is the problem ?
  Seems that the process stdout stream is empty, or a least it looks like from the debugging. I tried using CopyToAsync with another declared memory stream just before process.WaitForExit() ; but it gave me the same exception every time.

  If I use the console with the same command line and I redirect all stdout to a file (1> image.png) the image is readable... so I cannot understand why it does not work properly.

  Thanks in advance.