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• RTP Timestamps Are Not Monotonically increasing

  25 août 2019, par Fr0sty

  I am finding it a bit difficult trying to understand whether or not the hack around with FFmpeg and OpenCV really provided a RTP timestamp. My last post helped a little bit but got me stuck in trying to validate the timestamps obtained through this work around by modifying ffmpeg and opencv.

  FFmpeg version : 4.1.0
  OpenCV version : 3.4.1

  import cv2
  
  import time
  
  from datetime import datetime, date
  
  
  
  uri = 'rtsp://admin:password@192.168.1.66:554/Streaming/Channels/101'
  
  cap = cv2.VideoCapture(uri)
  
  '''One is the offset between the two epochs. Unix uses an epoch located at 1/1/1970-00:00h (UTC) and NTP uses 1/1/1900-00:00h.
  
  This leads to an offset equivalent to 70 years in seconds (there are 17 leap years between the two dates so the offset is'''
  
  time_offset = 2208988800 # (70*365 + 17)*86400 = 2208988800 (in seconds)
  
  # offset = 3775484294
  
  days = 43697
  
  pdat = "1900-01-01 00:00:00:00"
  
  mdat = "2019-08-23 22:02:44:00" # str(datetime.now()) + str(datetime.now().time())
  
  pdate = datetime.strptime(pdat, "%Y-%m-%d %H:%M:%S:%f").date()
  
  mdate = datetime.strptime(mdat, "%Y-%m-%d %H:%M:%S:%f").date()
  
  delta = (mdate - pdate).days
  
  offset = delta * 86400
  
  def time_delta(s):
  
      return (s - time_offset)
  
  
  
  while True:
  
      frame_exists, curr_frame = cap.read()
  
      if frame_exists:
  
          seconds = cap.getRTPTimeStampSeconds()
  
          fraction = cap.getRTPTimeStampFraction()
  
          timestamp = cap.getRTPTimeStampTs()
  
          unix_offset = seconds - time_offset
  
          msec = int((int(fraction) / 0xFFFFFFFF) * 1000.0)
  
          ts = float(str(unix_offset) + "." + str(msec))
  
          # print("Timestamp per Frame:%i" % timestamp)
  
          print((datetime.fromtimestamp(float(ts) + offset)))
  
  cap.release()

  My Output :

  On August 23, 2019 at 22:02

  ...
  
  2019-08-23 13:59:52.781000
  
  2019-08-23 13:59:52.726000
  
  2019-08-23 13:59:52.671000
  
  2019-08-23 13:59:52.616000
  
  2019-08-23 13:59:52.561000
  
  2019-08-23 13:59:52.506000
  
  2019-08-23 13:59:52.451000
  
  2019-08-23 13:59:52.396000
  
  2019-08-23 13:59:52.342000
  
  2019-08-23 13:59:52.287000
  
  2019-08-23 13:59:52.232000
  
  2019-08-23 13:59:52.177000
  
  2019-08-23 13:59:52.122000
  
  2019-08-23 13:59:52.067000
  
  2019-08-23 13:59:52.012000
  
  2019-08-23 13:59:53.570000
  
  2019-08-23 13:59:53.020000
  
  2019-08-23 13:59:53.847000
  
  2019-08-23 13:59:53.792000

  I’ve noticed how the time increments weirdly (that’s not suppose to happen in the real, current time), such as the last two lines and a few others in between in the output. A bit flabbergasted as to what went wrong. Also trying this out on multiple IP cameras, with each showing a different timestamp probably related to when they were turned on.

• Having trouble obtaining the time from RTP Timestamps obtained through OpenCV

  24 août 2019, par Fr0sty

  I am finding it a bit difficult trying to understand whether or not the hack around with FFmpeg and OpenCV really provided a RTP timestamp. My last post helped a little bit but got me stuck in trying to validate the timestamps obtained through this work around by modifying ffmpeg and opencv.

  FFmpeg version : 4.1.0
  OpenCV version : 3.4.1

  import cv2
  
  import time
  
  from datetime import datetime, date
  
  
  
  uri = 'rtsp://admin:password@192.168.1.66:554/Streaming/Channels/101'
  
  cap = cv2.VideoCapture(uri)
  
  '''One is the offset between the two epochs. Unix uses an epoch located at 1/1/1970-00:00h (UTC) and NTP uses 1/1/1900-00:00h.
  
  This leads to an offset equivalent to 70 years in seconds (there are 17 leap years between the two dates so the offset is'''
  
  time_offset = 2208988800 # (70*365 + 17)*86400 = 2208988800 (in seconds)
  
  # offset = 3775484294
  
  days = 43697
  
  pdat = "1900-01-01 00:00:00:00"
  
  mdat = "2019-08-23 22:02:44:00" # str(datetime.now()) + str(datetime.now().time())
  
  pdate = datetime.strptime(pdat, "%Y-%m-%d %H:%M:%S:%f").date()
  
  mdate = datetime.strptime(mdat, "%Y-%m-%d %H:%M:%S:%f").date()
  
  delta = (mdate - pdate).days
  
  offset = delta * 86400
  
  def time_delta(s):
  
      return (s - time_offset)
  
  
  
  while True:
  
      frame_exists, curr_frame = cap.read()
  
      if frame_exists:
  
          seconds = cap.getRTPTimeStampSeconds()
  
          fraction = cap.getRTPTimeStampFraction()
  
          timestamp = cap.getRTPTimeStampTs()
  
          unix_offset = seconds - time_offset
  
          msec = int((int(fraction) / 0xFFFFFFFF) * 1000.0)
  
          ts = float(str(unix_offset) + "." + str(msec))
  
          # print("Timestamp per Frame:%i" % timestamp)
  
          print((datetime.fromtimestamp(float(ts) + offset)))
  
  cap.release()

  My Output :

  On August 23, 2019 at 22:02

  ...
  
  2019-08-23 13:59:52.781000
  
  2019-08-23 13:59:52.726000
  
  2019-08-23 13:59:52.671000
  
  2019-08-23 13:59:52.616000
  
  2019-08-23 13:59:52.561000
  
  2019-08-23 13:59:52.506000
  
  2019-08-23 13:59:52.451000
  
  2019-08-23 13:59:52.396000
  
  2019-08-23 13:59:52.342000
  
  2019-08-23 13:59:52.287000
  
  2019-08-23 13:59:52.232000
  
  2019-08-23 13:59:52.177000
  
  2019-08-23 13:59:52.122000
  
  2019-08-23 13:59:52.067000
  
  2019-08-23 13:59:52.012000
  
  2019-08-23 13:59:53.570000
  
  2019-08-23 13:59:53.020000
  
  2019-08-23 13:59:53.847000
  
  2019-08-23 13:59:53.792000

  I’ve noticed how the time increments weirdly (that’s not suppose to happen in the real, current time), such as the last two lines and a few others in between in the output. A bit flabbergasted as to what went wrong. Also trying this out on multiple IP cameras, with each showing a different timestamp probably related to when they were turned on.

• C# Bitmap to AVI / WMV with Compression

  5 juillet 2019, par Digitalsa1nt

  Prelude :

  I’m going to preface this with, I have been learning C# in my spare time at work, and that I have been staring at code for a solid two days trying to wrap my head around this problem. I am developing some software to be used with a visualiser that connects by USB to a standard Desktop PC, the software detects the capture device and loads frames into bitmap using a New Frame Event, this is then displayed in a ’picture box’ as a live video stream. The problem as it sits is trying to encorporate the ability to record the stream and save to file, preferably a WMV or a compressed AVI.

  What’s been tried :

  I have considered and looked into the following :

  SharpAVI - cant seem to get this to compress or save the frames properly as it appears to mainly look at existing AVI files.

  AForge.Video.VFW - AVI files can be created but are far too large to be used, due to restrictions on the user areas of the individuals who will be using this software.

  AForge.Video.FFMPEG - Again due to considerations of those using this software I can’t have unmanaged DLL’s sat in the output folder with the Executable file, and unfortunately this particular DLL cant be compiled properly using Costura Fody.

  AVIFile Library Wrapper (From Code Project) - Again can’t seem to get this to compress a stream correctly from Bitmaps from the New Frame Events.

  DirectShow - Appears to use C++ and unfortunately is beyond my skill level at this time.

  The Relevant Code Snippets :

  Current References :

  using System.Data;
  
  using System.Drawing;
  
  using System.Linq;
  
  using System.Text;
  
  using System.Threading.Tasks;
  
  using System.Windows.Forms;
  
  using System.Resources;
  
  using System.Drawing.Imaging;
  
  using System.IO;
  
  //Aforge Video DLL's
  
  using AForge.Video;
  
  using AForge.Video.VFW;
  
  using AForge.Video.DirectShow;
  
  //Aforge Image DLL's
  
  using AForge.Imaging;
  
  using AForge.Imaging.Formats;
  
  using AForge.Imaging.Filters;
  
  //AviLibrary
  
  using AviFile;

  Global Variables :

      #region Global Variables
  
  
  
      private FilterInfoCollection CaptureDevice; // list of available devices
  
      private VideoCaptureDevice videoSource;
  
      public System.Drawing.Image CapturedImage;
  
  
  
      bool toggleMic = false;
  
  
  
      bool toggleRec = false;
  
      //aforge
  
      AVIWriter aviWriter;
  
      Bitmap image;
  
  
  
  
  
      #endregion

  Code for Displaying Stream

      #region Displays the Stream
  
  
  
      void videoSource_NewFrame(object sender, NewFrameEventArgs eventArgs)
  
      {
  
          picBoxStream.SizeMode = PictureBoxSizeMode.Zoom;
  
          picBoxStream.Image = (Bitmap)eventArgs.Frame.Clone();// clones the bitmap
  
  
  
  
  
          if (toggleRec == true)
  
          {
  
              image = (Bitmap)eventArgs.Frame.Clone();
  
              aviWriter.AddFrame(image);
  
          }
  
      }
  
  
  
      #endregion

  Current Code for Recording Stream

      #region Record Button
  
  
  
      private void btnRecord_Click(object sender, EventArgs e)
  
      {
  
          if (toggleRec == false)
  
          {
  
              saveAVI = new SaveFileDialog();
  
              saveAVI.Filter = "AVI Files (*.avi)|*.avi";
  
  
  
              if (saveAVI.ShowDialog() == DialogResult.OK)
  
              {
  
                  aviWriter = new AVIWriter();
  
                  aviWriter.Open(saveAVI.FileName, 1280, 720);
  
  
  
                  toggleRec = true;
  
                  Label lblRec = new Label();
  
              }
  
  
  
          }
  
          else if (toggleRec == true)
  
          {
  
              aviWriter.Close();
  
              toggleRec = false;
  
          }
  
      }
  
  
  
      #endregion

  I apoligise if the above code doesn’t look quite right, I have been swapping, changing and recoding those three sections a lot in order to find a working combination. This means that it’s rather untidy but I didn’t see the point in cleaning it all up until I had the code working. That being said really any help that you can provide is greatfully recieved, even if it’s a case of what I want to do just cannot be done.

  Thank you in advance.

  EDIT : 2019 :

  It’s been awhile since I posted this and it still gets the odd bit of interest here and there. Back when I posted this I was teaching myself to code and I had this weird quirk that I didn’t like using 3rd party libraries if I could avoid it, I wanted to do my own work, since then I’ve learnt a lot and one of those things is that the open source world is immense, impressive and kind. So if there is a 3rd party library that does what you want just use it, it’ll save you time.