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• How to decode RTSP h264 stream from IP camera using C# and EMGUCV ?

  9 janvier 2020, par xor31four

  I am trying to access a H.264 stream on an IP camera within my LAN via EmguCV Video Capture. There is an RTSP URL containing the h.264 stream and an HTTP URL that transmits MJPEG.

  The goal is to perform perform some EmguCV video processing operations on a live stream in as close to real-time as possible.

  I have a bandwidth limitation of 10Mbps.

  The problem is that Emgu.CV is unable to open the rtsp(h264) stream but perfectly capable of opening the http(mjpeg) stream..

  I can’t use the mjpeg stream as it consumes too much bandwidth and I drastically lose picture quality and fps.

  I need to access the h.264 stream in order to meet my bandwidth requirements

  Here is the code that I use to check whether the capture has been created :

              string MJPEG_URL = "http://192.168.0.11:35271/image1"; //returns true
  
              string RTSP_URL = "rtsp://192.168.0.11/stream1.sdp"; //returns false
  
  
  
              _cam1 = new VideoCapture(RTSP_URL, VideoCapture.API.Any);
  
              var flag = _cam1.IsOpened;
  
              Console.WriteLine(flag);

  RTSP_URL returns false. But when I enter the exact same URL in VLC Player, or if I use VLCSharp library to access the stream it works.

  Any suggestions ?

• ffmpeg QSV hardware encoder with x11grab screen capture

  11 janvier 2020, par Toby Eggitt

  I believe I have built ffmpeg with support for my motherboard’s Intel graphics processor chip, but I have not succeeded in showing this working in any way. My goal is to use it for screen capture (the ffmpeg I built does capture screen successfully using the software encoding, but this is far too slow to be useful—it manages about 12fps at a very modest quality).

  My main problem—I think—is that I don’t know how to use these encoders, the examples I found all fail, which makes me suspect that what I’ve built is broken in some way. However, I also have no idea how I can verify that I built this correctly, but the following are true :

  • The five components that I built to get to this all compiled without
    errors (they were libva, gmmlib, intel-media-driver, libmfx, and
    ffmpeg
  • The output of ffmpeg -encoders includes four encoders with _qsv in
    their names including h264_qsv
  • Most of the commands I have tried result in output of this form :

      [h264_qsv @ 0x55ef1dc72040] Low power mode is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] Current frame rate is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] Current picture structure is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] Current resolution is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] Current pixel format is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] some encoding parameters are not supported by the QSV runtime. Please double check the input parameters.
  
      Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

  I have the impression this thing might be fussy about many parameters of this sort but have no idea where to find out what it would like. Any suggestions at all, how to verify it, or better yet, how to issue a command that captures screen and encodes with the hardware, would be most welcome.

• FFmpeg truncates untrunc'ed video

  18 mars 2020, par petrpulc

  Background : Colleague's Panasonic consumer camera had issues with high-capacity SD card and yielded two different types of truncated files (mp4 and mdt) with both header and index corrupted. Both were "fixable" with following steps :

  



  

  1. Locate with hex editor the ascii sequence "mdat" in both a truncated and a corresponding known good file. In mp4 the "mdat" is quite deep in the file as it contains some (but bad) headers, the mdt type almost starts with it.

  


  2. Replace everything up to the "mdat" sequence with known good header. BUT this also means that metadata on length are copied over.

  


  3. Run https://github.com/ponchio/untrunc on the file with corrected header (it refused to run on original files).

  


  4. Profit ! VLC plays the file fine, ffprobe shows correct length. BUT ffmpeg encoding stops at the end timecode of the file I taken the known good header from in step 2.

  


  5. A somewhat ugly solution is to recode the file in VLC (video copy seems to be breaking file up again).

  


  



  I am wondering if I overlooked something ; big time. I guess I do, but simple timecode operations on input file do not seem to have any effect at all.

  



  Is there a way to persuade ffmpeg to encode the whole file that ffprobe and VLC see ?

  



  Files may be provided for analysis on personal basis only, sorry.