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• 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.

• 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!");
  
          }
  
      }

• Using ffmpeg with Flash Media Server and HDS

  20 avril 2012, par Jonathan

  I want to use ffmpeg to encode and publish a live stream to Flash Media Server. In order to support iOS devices, I need to implement HTTP Live Streaming as well. The video needs to be in H.264 format and the audio should be AAC. I don't have much experience working with ffmpeg, and I'm having a hard time getting this to work. This is the command that I've tried (and some variations as well) :

  ffmpeg.exe -threads 15 -f dshow -i video="USB2.0 UVC WebCam":audio="Microphone (Realtek High Defini" \
  
        -map_channel 0.1.1 -r 24 -acodec libvo_aacenc -ar 22050 -ab 128k -vcodec libx264 \
  
        -s vga -vb 100k -f flv "rtmp:///livepkgr/livestream1?adbe-live-event=liveevent" \
  
        -r 24 -acodec libvo_aacenc -ar 22050 -ab 128k -vcodec libx264 -s qvga -vb 200k \
  
        -f flv "rtmp:///livepkgr/livestream2?adbe-live-event=liveevent" \
  
        -r 24 -acodec libvo_aacenc -ar 22050 -ab 128k -vcodec libx264 -s vga -vb 350k 
  
        -f flv "rtmp:///livepkgr/livestream3?adbe-live-event=liveevent"

  When I run this, it appears to connect to FMS, but then I get a lot of error messages about dropped frames - I'm not sure if ANY frames get encoded successfully. My CPU usage is very high as well. I get a 404 error from FMS when I enter the URL of the *.m3u8 file for one of the individual streams (the main livestream.m3u8 file is accessible though). I have also tried outputting to a file instead of FMS, with no success. All I get is some very garbled sound and no video.

  Any suggestions for what options/commands I should use to get this working ? Is anyone using ffmpeg with FMS to do HTTP Dynamic Streaming / HLS with MP4 video ? I've been struggling to get HDS/HLS working for some time now, and any help would be much appreciated ! It shouldn't make a difference, but I'm using FMS on Amazon EC2 with their AMI image.

  Thanks !