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• Problem trimming / excerpting MP4 with FFmpeg

  18 novembre 2022, par Spencer Graves

  The video is black in the first almost 2 seconds of an MP4 file created by "ffmpeg -i Sorrell2022-11-16.mp4 -ss 2:46 -to 41:49 -c:v copy Sorrell2022-11-17a.mp4". "input.mp4" [Sorrell2022-11-16.mp4] and "output.mp4" [Sorrell2022-11-17a.mp4] are available in :

  


  https://drive.google.com/drive/folders/1vSRODTQ04XKNr1iDF6bOYwmcuTHxnKGa?usp=sharing

  


  


  1. How can I get ffmpeg to properly perform this trim / excerpt task — without substituting black for the images in the first not quite 2 seconds ?

     


  


  2. What should I do to upgrade ffmpeg to the latest ? My primary computer is running macOS Big Sur 11.7.1. "brew update && brew upgrade ffmpeg" didn't work for me. I've run "brew update" separately, getting now, "Already up-to-date." "brew upgrade ffmpeg" says, "Error : ffmpeg not installed". It's clear that ffmpeg is installed and working, but brew cannot find it. I saw advice to uninstall ffmpeg and reinstall it from scratch. However, I'm reluctant to do that, because I sometimes use "ffmpeg -i input.mp4 -c:v libvpx-vp9 -b:v 2M -pass 1 -an -f null /dev/null" followed by "ffmpeg -i input.mp4 -c:v libvpx-vp9 -b:v 2M -pass 2 -c:a libopus output.webm", and this did NOT work on my Mac until the last time I reformatted my hard drive and reinstalled everything. Maybe I should not worry about this.

     


  


  


  Suggestions ? Thanks, Spencer Graves

  


• Why i'm getting strange video file when using ffmpeg and pipes to create video file in real time ?

  30 juin 2015, par Brubaker Haim

  The goal here is to create a compressed mp4 video file in real time.
  I’m saving screenshots as bitmaps type on my hard disk.
  And i want to create mp4 file and compress the mp4 video file in real time.

  The problem is the end the video file i get looks very strange.
  This is the result : Strange Video File

  The class that i’m using the ffmpeg with arguments.

  using System;
  
  using System.Windows.Forms;
  
  using System.Collections.Generic;
  
  using System.Linq;
  
  using System.Text;
  
  using System.Threading.Tasks;
  
  using System.Drawing;
  
  using System.IO.Pipes;
  
  using System.Runtime.InteropServices;
  
  using System.Diagnostics;
  
  using System.IO;
  
  using DannyGeneral;
  
  
  
  namespace Youtube_Manager
  
  {
  
      class Ffmpeg
  
      {
  
          NamedPipeServerStream p;
  
          String pipename = "mytestpipe";
  
          System.Diagnostics.Process process;
  
          string ffmpegFileName = "ffmpeg.exe";
  
          string workingDirectory;
  
  
  
          public Ffmpeg()
  
          {
  
              workingDirectory = Path.GetDirectoryName(Application.ExecutablePath);
  
              Logger.Write("workingDirectory: " + workingDirectory);
  
              if (!Directory.Exists(workingDirectory))
  
              {
  
                  Directory.CreateDirectory(workingDirectory);
  
              }
  
              ffmpegFileName = Path.Combine(workingDirectory, ffmpegFileName);
  
              Logger.Write("FfmpegFilename: " + ffmpegFileName);
  
          }
  
  
  
          public void Start(string pathFileName, int BitmapRate)
  
          {
  
              try
  
              {
  
  
  
                  string outPath = pathFileName;
  
                  p = new NamedPipeServerStream(pipename, PipeDirection.Out, 1, PipeTransmissionMode.Byte);
  
  
  
                  ProcessStartInfo psi = new ProcessStartInfo();
  
                  psi.WindowStyle = ProcessWindowStyle.Hidden;
  
                  psi.UseShellExecute = false;
  
                  psi.CreateNoWindow = false;
  
                  psi.FileName = ffmpegFileName;
  
                  psi.WorkingDirectory = workingDirectory;
  
                  psi.Arguments = @"-f rawvideo -pix_fmt yuv420p -video_size 1920x1080 -i \\.\pipe\mytestpipe -map 0 -c:v mpeg4 -r " + BitmapRate + " " + outPath;
  
                  //psi.Arguments = @"-framerate 1/5 -i -c:v libx264 -r 30 -pix_fmt yuv420p \\.\pipe\mytestpipe -map 0 -c:v mpeg4 -r" + BitmapRate + " " + outPath;
  
                  process = Process.Start(psi);
  
                  process.EnableRaisingEvents = false;
  
                  psi.RedirectStandardError = true;
  
                  p.WaitForConnection();
  
              }
  
              catch (Exception err)
  
              {
  
                  Logger.Write("Exception Error: " + err.ToString());
  
              }
  
          }
  
  
  
          public void PushFrame(Bitmap bmp)
  
          {
  
              try
  
              {
  
                  int length;
  
                  // Lock the bitmap's bits.
  
                  //bmp = new Bitmap(1920, 1080);
  
                  Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
  
                  //Rectangle rect = new Rectangle(0, 0, 1280, 720);
  
                  System.Drawing.Imaging.BitmapData bmpData =
  
                      bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadOnly,
  
                      bmp.PixelFormat);
  
  
  
                  int absStride = Math.Abs(bmpData.Stride);
  
                  // Get the address of the first line.
  
                  IntPtr ptr = bmpData.Scan0;
  
  
  
                  // Declare an array to hold the bytes of the bitmap.
  
                  //length = 3 * bmp.Width * bmp.Height;
  
                  length = absStride * bmpData.Height;
  
                  byte[] rgbValues = new byte[length];
  
  
  
                  //Marshal.Copy(ptr, rgbValues, 0, length);
  
                  int j = bmp.Height - 1;
  
                  for (int i = 0; i < bmp.Height; i++)
  
                  {
  
                      IntPtr pointer = new IntPtr(bmpData.Scan0.ToInt32() + (bmpData.Stride * j));
  
                      System.Runtime.InteropServices.Marshal.Copy(pointer, rgbValues, absStride * (bmp.Height - i - 1), absStride);
  
                      j--;
  
                  }
  
                  p.Write(rgbValues, 0, length);
  
                  bmp.UnlockBits(bmpData);
  
              }
  
              catch(Exception err)
  
              {
  
                  Logger.Write("Error: " + err.ToString());
  
              }
  
  
  
          }
  
  
  
          public void Close()
  
          {
  
              p.Close();
  
          }
  
      }
  
  }

  Then i’m using the method PushFrame here in this class :

  public Bitmap GetScreenShot(string folder, string name)
  
      {
  
          _screenShot = new Bitmap(GetScreen());
  
          System.GC.Collect();
  
          System.GC.WaitForPendingFinalizers();
  
          string ingName = folder + name +  images.counter.ToString("D6") + ".bmp";
  
          _screenShot.Save(ingName,System.Drawing.Imaging.ImageFormat.Bmp);
  
          fmpeg.PushFrame(_screenShot);
  
          _screenShot.Dispose();
  
  
  
          return _screenShot;
  
      }

  The Bitmaps on the hard disk are fine i can edit/open see them.
  When using command prompt and manually type ffmpeg command it does compress and create a mp4 video file.

  But when using the Ffmpeg class i did with the PushFrame method it’s creating this strange video file.

  This is a link for my OneDrive with 10 screenshots images files for testing :

  screenshots rar

  Sample screenshot from the video file when playing the video file :
  Looks very choppy. The Bitmaps on the hard disk each one is 1920x1080 and Bit depth 32

  But it dosen’t look like that in the video file :

  

  This is the arguments i’m using :

  psi.Arguments = @"-f rawvideo -vcodec rawvideo -pix_fmt rgb24 -video_size 1920x1080 -i \\.\pipe\mytestpipe -map 0 -c:v mpeg4 -r " + BitmapRate + " " + outPath;

  The video size is very small 1.24 MB

• lavu/video_enc_params : Avoid relying on an undefined C construct

  15 janvier 2023, par Martin Storsjö

  lavu/video_enc_params : Avoid relying on an undefined C construct
  The construct of using offsetof on a (potentially anonymous) struct
  
  defined within the offsetof expression, while supported by all
  
  current compilers, has been declared explicitly undefined by the
  
  C standards committee [1].
  Clang recently got a change to identify this as an issue [2] ;
  
  initially it was treated as a hard error, but it was soon after
  
  softened into a warning under the -Wgnu-offsetof-extensions option
  
  (not enabled automatically as part of -Wall though).
  Nevertheless - in this particular case, it's trivial to fix the
  
  code not to rely on the construct that the standards committee has
  
  explicitly called out as undefined.
  [1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm
  
  [2] https://reviews.llvm.org/D133574
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavutil/video_enc_params.c