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• OpenCV and GoPro - empty frames in VideoCapture stream

  19 mai 2014, par Novatar

  I have a GoPro Hero 3+ (Black) which is connected to a video capture card (AverMedia Game Broadcaster HD). I simply want to get the video stream in OpenCV. With a Logitech Webcam there are no problems. The used code is below.

  VideoCapture cap;
  
  cap.open(0);
  
  
  
  waitKey(300);
  
  
  
  //cap.set(CV_CAP_PROP_FRAME_WIDTH, 1280);
  
  //cap.set(CV_CAP_PROP_FRAME_HEIGHT, 720);
  
  
  
  if (cap.isOpened()){
  
      cout << "Cam identified" << endl;
  
  }
  
  
  
  namedWindow("dst", 1);
  
  
  
  while (1){
  
  
  
  Mat frame;
  
  
  
  if (!cap.read(frame)) {
  
      std::cout << "Unable to read frame from video stream" << std::endl;
  
      continue;
  
  }
  
  
  
  imshow("dst", frame);
  
  
  
  [...]
  
  
  
  }

  With the GoPro the following happens : OpenCV is able to open the VideoCapture ("Cam identified") but can’t read any frames (just a gray screen and the output : "Unable to read frame from video stream"). I also checked this with frame.empty() ;.

  I know that the video capture card works correct because Unity opens a WebCamTexture with the GoPro stream without any issues. I read about codec problems in OpenCv and so I already tried to compile OpenCV with FFMPEG support. Now the recorded MP4-Videos of the GoPro can be displayed but the stream still doesn’t work.

  I use OpenCV 2.48, Windows 7 and Visual Studio 2013.

  ---

  EDIT : Here is the code of libVLC solution :

  struct ctx
  
  {
  
  uint8_t* pixeldata;
  
  std::mutex imagemutex;
  
  };
  
  
  
  static void display(void *data, void *id);
  
  static void unlock(void *data, void *id, void *const *p_pixels);
  
  static void *lock(void *data, void **p_pixels);
  
  
  
  struct ctx ctx;
  
  
  
  libvlc_instance_t *inst;
  
  libvlc_media_player_t *mp;
  
  libvlc_media_t *m;
  
  
  
  int main(int argc, char* argv[])
  
  {
  
      ctx.pixeldata = new uint8_t[1280 * 720 * 3];
  
  
  
      char const *vlc_argv[] =
  
      {
  
          "-vvv",
  
          "--no-audio", /* skip any audio track */
  
          "--no-xlib", /* tell VLC to not use Xlib */
  
      };
  
  
  
      int vlc_argc = sizeof(vlc_argv) / sizeof(*vlc_argv);
  
      inst = libvlc_new(vlc_argc, vlc_argv);
  
  
  
      const char *options[] =
  
      {
  
          ":dshow-vdev=AVerMedia HD Capture",
  
          ":dshow-adev=none",
  
          //":dshow-size=1280x720",
  
          ":dshow-fps=24",
  
          ":dshow-chroma=YUY2",
  
          ":dshow-video-input=1",
  
          ":dshow-video-output=1",
  
          ":dshow-aspect-ratio=16\:9",
  
          ":live-caching=80",
  
          NULL
  
      };
  
  
  
      m = libvlc_media_new_location(inst, "dshow://");
  
      for (const char **opt = options; *opt; opt++)
  
          libvlc_media_add_option(m, *opt);
  
  
  
      mp = libvlc_media_player_new_from_media(m);
  
      libvlc_media_release(m);
  
      libvlc_video_set_callbacks(mp, lock, unlock, display, &ctx);
  
      libvlc_video_set_format(mp, "RV24", 1280, 720, 1280 * 3);
  
      libvlc_media_player_play(mp);
  
  
  
      namedWindow("all", 1);
  
  
  
      Mat frame(720, 1280, CV_8UC3);
  
  
  
      while (1){
  
  
  
          ctx.imagemutex.lock();
  
          memcpy(gesamt.data, ctx.pixeldata, 1280 * 720 * sizeof(uint8_t) * 3);
  
          ctx.imagemutex.unlock();
  
  
  
          imshow("all", gesamt);
  
  
  
          if (waitKey(30) == 27) //wait for 'esc' key press for 30ms. If 'esc' key is pressed, break loop
  
          {
  
              cout << "esc key is pressed by user" << endl;
  
              break;
  
          }
  
  
  
      }
  
  
  
      libvlc_media_player_stop(mp);
  
      libvlc_media_player_release(mp);
  
      libvlc_release(inst);
  
      delete[] ctx.pixeldata;
  
  
  
      return 0;
  
  }
  
  
  
  void display(void *data, void *id){
  
      (void)data;
  
      assert(id == NULL);
  
  }
  
  
  
  void unlock(void *data, void *id, void *const *p_pixels){
  
      struct ctx *ctx = (struct ctx*)data;
  
      ctx->imagemutex.unlock();
  
      assert(id == NULL);
  
  }
  
  
  
  void *lock(void *data, void **p_pixels){
  
      struct ctx *ctx = (struct ctx*)data;
  
      ctx->imagemutex.lock();
  
      *p_pixels = ctx->pixeldata;
  
      return NULL;
  
  }

• Using ffmpeg for capturing (and recording) audio and video from decklink card using Windows 7 [closed]

  30 septembre 2015, par user3540580

  Im new with ffmpeg. I am trying to capture the video + audio from Decklink capture device. However I had some problems, I don’t know which stream using for my current video + audio source that connected to the decklink card’s SDI port. Could someone tell me how to find out the streaming information.

  Here is my information :

  ffmpeg -list_devices true -f dshow -i dummy

  C:\Users\Streaming>ffmpeg -list_devices true -f dshow -i dummy ffmpeg version N-52941-g13cb6ed Copyright (c) 2000-2013 the FFmpeg developers built on May 9 2013 17:24:42 with gcc 4.7.3 (GCC) configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab le-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetyp e --enable-libgsm --enable-libilbc --enable-libmp3lame --enable-libopencore-amrn b --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libr tmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheo ra --enable-libtwolame --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-li bvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-libxvid --ena ble-zlib libavutil 52. 30.100 / 52. 30.100 libavcodec 55. 7.100 / 55. 7.100 libavformat 55. 4.101 / 55. 4.101 libavdevice 55. 0.100 / 55. 0.100 libavfilter 3. 63.101 / 3. 63.101 libswscale 2. 3.100 / 2. 3.100 libswresample 0. 17.102 / 0. 17.102 libpostproc 52. 3.100 / 52. 3.100 [dshow @ 0000000000306d00] DirectShow video devices [dshow @ 0000000000306d00] "Blackmagic WDM Capture" [dshow @ 0000000000306d00] "Decklink Video Capture" [dshow @ 0000000000306d00] DirectShow audio devices [dshow @ 0000000000306d00] "Line In (High Definition Audio " [dshow @ 0000000000306d00] "Decklink Audio Capture" [dshow @ 0000000000306d00] "Microphone (Total Recorder WDM " dummy: Immediate exit requested

  ffmpeg -list_options true -f dshow -i video="Decklink Video Capture"

  C:\Users\Streaming>ffmpeg -list_options true -f dshow -i video="Decklink Video C apture" ffmpeg version N-52941-g13cb6ed Copyright (c) 2000-2013 the FFmpeg developers built on May 9 2013 17:24:42 with gcc 4.7.3 (GCC) configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab le-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetyp e --enable-libgsm --enable-libilbc --enable-libmp3lame --enable-libopencore-amrn b --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libr tmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheo ra --enable-libtwolame --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-li bvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-libxvid --ena ble-zlib libavutil 52. 30.100 / 52. 30.100 libavcodec 55. 7.100 / 55. 7.100 libavformat 55. 4.101 / 55. 4.101 libavdevice 55. 0.100 / 55. 0.100 libavfilter 3. 63.101 / 3. 63.101 libswscale 2. 3.100 / 2. 3.100 libswresample 0. 17.102 / 0. 17.102 libpostproc 52. 3.100 / 52. 3.100 [dshow @ 00000000002fa080] DirectShow video device options [dshow @ 00000000002fa080] Pin "Capture" [dshow @ 00000000002fa080]
  
  pixel_format=uyvy422 min s=720x486 fps=29.97 max s =720x486 fps=29.97 [dshow @ 00000000002fa080] pixel_format=uyvy422 min s=720x486 fps=23.976 max s=720x486 fps=23.976 [dshow @ 00000000002fa080] pixel_format=uyvy422 min s=720x576 fps=25 max s=72 0x576 fps=25 [dshow @ 00000000002fa080] pixel_format=uyvy422 min s=1920x1080 fps=23.976 ma x s=1920x1080 fps=23.976 [dshow @ 00000000002fa080] pixel_format=uyvy422 min s=1920x1080 fps=24 max s= 1920x1080 fps=24 [dshow @ 00000000002fa080] pixel_format=uyvy422 min s=1920x1080 fps=25 max s= 1920x1080 fps=25 [dshow @ 00000000002fa080] pixel_format=uyvy422 min s=1920x1080 fps=29.97 max s=1920x1080 fps=29.97 [dshow @ 00000000002fa080]
  
  pixel_format=uyvy422 min s=1920x1080 fps=30 max s= 1920x1080 fps=30 [dshow @ 00000000002fa080] pixel_format=uyvy422 min s=1280x720 fps=50 max s=1 280x720 fps=50 [dshow @ 00000000002fa080]
  
  pixel_format=uyvy422 min s=1280x720 fps=59.9402 ma x s=1280x720 fps=59.9402 [dshow @ 00000000002fa080] pixel_format=uyvy422 min s=1280x720 fps=60.0002 ma x s=1280x720 fps=60.0002 [dshow @ 00000000002fa080] vcodec=v210 min s=720x486 fps=29.97 max s=720x486 fps=29.97 [dshow @ 00000000002fa080] vcodec=v210 min s=720x486 fps=23.976 max s=720x486 fps=23.976 [dshow @ 00000000002fa080]
  
  vcodec=v210 min s=720x576 fps=25 max s=720x576 fps =25 [dshow @ 00000000002fa080] vcodec=v210 min s=1920x1080 fps=23.976 max s=1920x 1080 fps=23.976 [dshow @ 00000000002fa080]
  
  vcodec=v210 min s=1920x1080 fps=24 max s=1920x1080 fps=24 [dshow @ 00000000002fa080] vcodec=v210 min s=1920x1080 fps=25 max s=1920x1080 fps=25 [dshow @ 00000000002fa080] vcodec=v210 min s=1920x1080 fps=29.97 max s=1920x1 080 fps=29.97 [dshow @ 00000000002fa080] vcodec=v210 min s=1920x1080 fps=30 max s=1920x1080 fps=30 [dshow @ 00000000002fa080] vcodec=v210 min s=1280x720 fps=50 max s=1280x720 f ps=50 [dshow @ 00000000002fa080]
  
  vcodec=v210 min s=1280x720 fps=59.9402 max s=1280x 720 fps=59.9402 [dshow @ 00000000002fa080] vcodec=v210 min s=1280x720 fps=60.0002 max s=1280x 720 fps=60.0002 video=Decklink Video Capture: Immediate exit requested

• sws_freeContext/sws_scale/sws_getContext errors while compiling ffmpeg libraries

  17 avril 2014, par Steve

  I have been working on ffmpeg for one of my projects. I am trying to utilize the ffmpeg static or shared libraries for my Android x86 project. I have followed the steps provided by Intel on this weblink https://software.intel.com/en-us/android/blogs/2013/12/06/building-ffmpeg-for-android-on-x86. When I try to build my project, I encountered a three errors. I have been trying to rectify them from the past one week, I have tried all possible methods with no results.

  jni/jniplayer/jniplayer.cpp:1244 : error : undefined reference to 'sws_freeContext'
  jni/jniplayer/jniplayer.cpp:1384 : error : undefined reference to 'sws_scale'
  jni/jniplayer/jniplayer.cpp:1371 : error : undefined reference to 'sws_getContext'

  I have used arm libraries previously to build my Android arm project that compiled with no problems. Maybe, I am missing a few steps with x86. As all the above errors are generated only with x86.

  I suppose that the issue resides with the enabling of the macro for x86 platform.

  #if ARCH_ARM
  
  #define USE_SWSCALE 0
  
  #else
  
  #define USE_SWSCALE 1
  
  #endif

  Only when USE_SWSCALE is enabled, functions such as sws_getcontext get enabled in ffmpeg.

  Have someone encountered such errors before. Kindly, please offer me some help with this issue. Thanks in advance for any answers.