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• How to check 'Output bit depth' of the libx264 library in ffmpeg ?

  25 mars 2014, par Amiramix

  According to the x264 Encoding Guide, the crf scale depends on whether x264 is 8-bit or 10-bit. Supposedly x264 --help shows the Output bit depth. But on Windows ffmpeg -h full doesn’t say anything about Output bit depth and the crf scale option is described as from -1 to FLT_MAX. How can I check if my ffmpeg is using 8-bit or 10-bit version of the libx264 library ?

• ffmpeg c# asp.net video conversion error

  3 mai 2012, par Arun Kumar

  The following code shows error as "StandardOut has not been redirected or the process hasn't started yet." What is the problem in this code ? It requires any changes ? It always clear the process by catch exception.

  static void ExecuteAsync()
  
              {
  
                  if (File.Exists("Videos/output.flv"))
  
                  try
  
                  {
  
                      File.Delete("Videos/output.flv");
  
                  }
  
                  catch
  
                  {
  
                      return;
  
                  }
  
  
  
              try
  
              {
  
                  process = new Process();
  
                  ProcessStartInfo info = new ProcessStartInfo(@"e:\ffmpeg\bin\ffmpeg.exe", "-i cars1.flv -same_quant intermediate1.mpg");
  
                  info.CreateNoWindow = false;
  
                  info.UseShellExecute = false;
  
                  info.RedirectStandardError = true;
  
                  info.RedirectStandardOutput = true;
  
                  process.StartInfo = info;
  
                  process.EnableRaisingEvents = true;
  
                  process.ErrorDataReceived += new DataReceivedEventHandler(process_ErrorDataReceived);
  
                  process.OutputDataReceived += new DataReceivedEventHandler(process_OutputDataReceived);
  
                  process.Exited += new EventHandler(process_Exited);
  
                  process.Start();
  
                  process.BeginOutputReadLine();
  
                  process.BeginErrorReadLine();
  
              }
  
              catch (Exception ex)
  
              {
  
                  if (process != null) process.Dispose();
  
              }
  
          }
  
          static int lineCount = 0;
  
          static void process_ErrorDataReceived(object sender, DataReceivedEventArgs e)
  
          {
  
              Console.WriteLine("Input line: {0} ({1:m:s:fff})", lineCount++, DateTime.Now);
  
              Console.WriteLine(e.Data);
  
              Console.WriteLine();
  
          }
  
  
  
          static void process_OutputDataReceived(object sender, DataReceivedEventArgs e)
  
          {
  
              Console.WriteLine("Output Data Received.");
  
          }
  
  
  
          static void process_Exited(object sender, EventArgs e)
  
          {
  
              process.Dispose();
  
              Console.WriteLine("Bye bye!");
  
          }
  
      }

• How to get the real, actual duration of an MP3 file (VBR or CBR) server-side

  25 septembre 2016, par SquareCat

  I used to calculate the duration of MP3 files server-side using ffmpeg - which seemed to work fine. Today i discovered that some of the calculations were wrong. Somehow, for some reason, ffmpeg will miscalculate the duration and it seems to happen with variable bit rate mp3 files only.

  When testing this locally, i noticed that ffmpeg printed two extra lines in green.

  Command used :

  ffmpeg -i song_9747c077aef8.mp3

  ffmpeg says :

  [mp3 @ 0x102052600] max_analyze_duration 5000000 reached at 5015510
  
  [mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate

  After a nice, warm google session, i discovered some posts on this, but no solution was found.

  I then tried to increase the maximum duration :

  ffmpeg -analyzeduration 999999999 -i song_9747c077aef8.mp3

  After this, ffmpeg returned only the second line :

  [mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate

  But in either case, the calculated duration was just plain wrong. Comparing it to VLC i noticed that there the duration is correct.

  After more research i stumbled over mp3info - which i installed and used.

  mp3info -p "%S" song_9747c077aef8.mp3

  mp3info then returned the CORRECT duration, but only as an integer, which i cannot use as i need a more accurate number here. The reason for this was explained in a comment below, by user blahdiblah - mp3info is simply pulling ID3 info from the file and not actually performing any calculations.

  I also tried using mplayer to retrieve the duration, but just as ffmpeg, mplayer is returning the wrong value.