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• Compressing videos from a smartphone

  21 septembre 2019, par fejesjoco

  I have a Nexus 6p with the stock camera. It’s set to record at 1080p, 30fps. Here’s a 5 second sample (11 MB).

  Videos from this phone come out at about 17 Mbps on average. I tried to compress it with ffmpeg with -c:v libx264 -crf 23 -preset veryslow, the result comes out at about 5.5 MB, which is about 9 Mbps.

  I think this bitrate is a bit too much. When I look at torrent file listings, I can see high quality videos at 3 GB in size on average, and if such a movie is 90 minutes long on average, that is about 4-5 Mbps which sounds okay.

  I’m wondering, why the big difference ? I can notice that my video is noisy/grainy (which is expected from a phone), and that might reduce compressibility. I tried a few ffmpeg filters, like hqdn3d and atadenoise, but the noise mostly remained (maybe I didn’t play with it enough). Then I figured, the video is also shaky (which is also expected), and that might reduce compressibility too (and even makes temporal noise filtering less effective). I tried to stabilize it with the deshake filter, but that didn’t help either.

  I know I could just limit the bandwidth to whatever I like, but there must be a reason why ffmpeg thinks it needs a high bandwidth to maintain a certain quality, and a lower bandwidth would just decrease the quality.

  Why do these videos have such a high bitrate ? What’s the best way to compress them more while keeping or even increasing their quality ?

• Merge videos in c# asp.net using ffmpeg

  3 juillet 2012, par Arun Kumar

  Is it possible to merge the two videos by c# asp.net with the help of ffmpeg. In the ffmpeg documentation they gave us cat command. But it wont works in asp.net. I thought it only for linux.

  cat intermediate1.mpg intermediate2.mpg > intermediate_all.mpg

  asp.net execute this command but there is no output. Help me.

  namespace demo
  
  {
  
      public partial class Default : System.Web.UI.Page
  
      {
  
          protected void Button2_Click(object sender, EventArgs e)
  
          {
  
              string strFile = "cars1.flv";
  
              MergeFiles(strFile);
  
          }
  
  
  
          public void MergeFiles(string strFile)
  
          {
  
              string strParam;
  
              string Path_FFMPEG = Server.MapPath("~/ffmpeg/bin/ffmpeg.exe");
  
  
  
              //Converting a video into mp4 format
  
              string strOrginal = Server.MapPath("~/Videos/");
  
              strOrginal = strOrginal + strFile;
  
              string strConvert = Server.MapPath("~/Videos/ConvertedFiles/");
  
              string strExtn = Path.GetExtension(strOrginal);
  
              if (strExtn != ".mp4")
  
              {
  
                  strConvert = strConvert + strFile.Replace(strExtn, ".mp4");
  
                  strParam  = "-i " + strOrginal + " " + strConvert;
  
                  //strParam = "-i " + strOrginal + " -same_quant " + strConvert;
  
                  process(Path_FFMPEG, strParam);
  
              }
  
  
  
              //Merging two videos               
  
              String video1 = Server.MapPath("~/Videos/Cars1.mp4");
  
              String video2 = Server.MapPath("~/Videos/ConvertedFiles/Cars2.mp4");
  
              String strResult = Server.MapPath("~/Videos/ConvertedFiles/Merge.mp4");
  
              //strParam = "-loop_input -shortest -y -i " + video1 + " -i " + video2 + " -acodec copy -vcodec mjpeg " + strResult;
  
  
  
              strParam = " -i " + video1 + " -i " + video2 + " -acodec copy -vcodec mjpeg " + strResult;
  
  
  
              process(Path_FFMPEG, strParam);
  
          }
  
  
  
          public void process(string Path_FFMPEG, string strParam)
  
          {
  
              try
  
              {
  
                  Process ffmpeg = new Process();
  
                  ProcessStartInfo ffmpeg_StartInfo = new ProcessStartInfo(Path_FFMPEG, strParam);
  
                  ffmpeg_StartInfo.UseShellExecute = false;
  
                  ffmpeg_StartInfo.RedirectStandardError = true;
  
                  ffmpeg_StartInfo.RedirectStandardOutput = true;
  
                  ffmpeg.StartInfo = ffmpeg_StartInfo;
  
                  ffmpeg_StartInfo.CreateNoWindow = true;
  
                  ffmpeg.EnableRaisingEvents = true;
  
                  ffmpeg.Start();
  
                  ffmpeg.WaitForExit();
  
                  ffmpeg.Close();
  
                  ffmpeg.Dispose();
  
                  ffmpeg = null;
  
              }
  
              catch (Exception ex)
  
              {
  
  
  
              }
  
          }
  
  
  
      }
  
  }

• FFMPEG concatenate 2 random and different videos

  7 mars 2019, par Abibad Abdou

  I am trying to make an app in which users can send a video and it will be concatenated with other videos automatically. So the videos are in random formats, but I am converting them before concatenation using this command :

  ffmpeg -y -i {orginalVideo.itsExtention} -vcodec wmv2 4.wmv

  For the concatenation I have the following command :

  ffmpeg -y -i concat.wmv -i 4.wmv -filter_complex "[0:0][0:1][1:0][1:1] concat=n=2:v=1:a=1" output.wmv

  but I get the following error

  Input link in1:v0 parameters (size 640x480, SAR 1:1) do not match the corresponding output link in0:v0 parameters (1080x1920, SAR 1:1)
  
  
  
  Failed to configure output pad on Parsed_concat_0
  
  Error reinitializing filters!
  
  Failed to inject frame into filter network: Invalid argument
  
  Error while processing the decoded data for stream #1:0

  Thank you for your answer