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• Webcam streaming from Mac using FFmpeg

  13 décembre 2019, par Galaxy

  I want to stream my webcam from Mac using FFmpeg.

  First I checked the supported devices using ffmpeg -f avfoundation -list_devices true -i ""

  Output :

  [AVFoundation input device @ 0x7fdf1bd03000] AVFoundation video devices:
  
  [AVFoundation input device @ 0x7fdf1bd03000] [0] USB 2.0 Camera #2
  
  [AVFoundation input device @ 0x7fdf1bd03000] [1] FaceTime HD Camera
  
  [AVFoundation input device @ 0x7fdf1bd03000] [2] Capture screen 0
  
  [AVFoundation input device @ 0x7fdf1bd03000] [3] Capture screen 1
  
  [AVFoundation input device @ 0x7fdf1bd03000] AVFoundation audio devices:
  
  [AVFoundation input device @ 0x7fdf1bd03000] [0] Built-in Microphone

  The device[0] is the webcam I want to use.

  ---

  Then I tried to capture the webcam using ffmpeg -f avfoundation -i "0" out.mpg

  Output :

  [avfoundation @ 0x7fe7f3810600] Selected framerate (29.970030) is not supported by the device
  
  [avfoundation @ 0x7fe7f3810600] Supported modes:
  
  [avfoundation @ 0x7fe7f3810600]   320x240@[120.101366 120.101366]fps
  
  [avfoundation @ 0x7fe7f3810600]   640x480@[120.101366 120.101366]fps
  
  [avfoundation @ 0x7fe7f3810600]   800x600@[60.000240 60.000240]fps
  
  [avfoundation @ 0x7fe7f3810600]   1024x768@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7fe7f3810600]   1280x720@[60.000240 60.000240]fps
  
  [avfoundation @ 0x7fe7f3810600]   1280x1024@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7fe7f3810600]   1920x1080@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7fe7f3810600]   320x240@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7fe7f3810600]   640x480@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7fe7f3810600]   800x600@[20.000000 20.000000]fps
  
  [avfoundation @ 0x7fe7f3810600]   1024x768@[6.000002 6.000002]fps
  
  0: Input/output error

  ---

  After that, I tried stream this webcam from my Mac using ffmpeg -f avfoundation -framerate 30 -i "0" -f mpeg1video -b 200k -r 30 -vf scale=1920:1080 http://127.0.0.1:8082/

  Output :

  [avfoundation @ 0x7f8515012800] An error occurred: The activeVideoMinFrameDuration passed is not supported by the device.  Use -activeFormat.videoSupportedFrameRateRanges to discover valid ranges.0: Input/output error

  ---

  I cannot capture or stream this webcam. However when I used the Facetime camera instead of this webcam, everything was OK. I’ve been searching for this problem for a few days, but still cannot fix it. Does anyone have experience with webcam and FFmpeg on Mac ?

• Android OpenCV - How can i read video files with using jni ?

  20 juin 2017, par Tiga

  I am developing an application using Android Opencv.

  This app, which I am developing, offers two operations.

  • The frame read from the camera is passed to Jni using native function
    Mat.getNativeObjAddr (), and the new image is returned through
    javaCameraView’s onCameraFrame() function
  • It reads a video clip inside Storage, processes each frame the same
    as # 1, and returns the resulting image via the onCameraFrame()
    function.

  First,function is implemented as simple as the following and works normally :

     @Override
  
      public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) 
  
      {
  
          if(inputFrame!=null){
  
                  Detect(inputFrame.rgba().getNativeObjAddr(), boardImage.getNativeObjAddr());
  
              }
  
              return boardImage;
  
          }
  
      }

  However, the problem occurred in the second operation.
  As far as I know, the files inside Java Storage are not readable by jni.

  I already tried FFmpegMediaPlayer or MediaMetadataRetriever through Google search. However, the getFrameAtTime () function provided by this MetadataRetriever took an average of 170ms when grabbing a bitmap to a specific frame of 1920 * 1080 image. What I have to develop is to show the video results in real time at 30 fps. In # 1, the native function Detect () takes about 2ms to process one frame.

  For these reasons, I want to do this.

  java sends a video’s path (eg : /storage/emulated/0/download/video.mp4) to jni, and native functions process the video one frame at a time, and display the result image on ’onCameraFrame’.

  Is there a proper way ? I look forward to your reply. Thank you !

• Saving animation using FFMPEG is cutting off subplot

  13 juin 2017, par Aklys

  I’m using the following code to save an animated figure with two plots :

  c_anim = animation.FuncAnimation(c_fig, c_animate, init_func=c_init, repeat=True,
  
                                   frames=len(main_df.reset_index()['DATE'].tolist()),
  
                                   interval=graph_interval_speed, blit=True)
  
  plt.rcParams['animation.ffmpeg_path'] = '.\\FFMPEG\\bin\\ffmpeg.exe'
  
  plt.rcParams['animation.bitrate'] = -1
  
  FFwriter = animation.FFMpegWriter(fps=30, codec='libx264', extra_args=['-s', '1080:1920', '-aspect', '16:9'])
  
  c_anim.save('basic_animation.mp4', writer=FFwriter, dpi=100)

  But the video file it outputs cuts off the second plot. The animation works fine with plt.show() and the figure or plot have not been given specific sizes.

  I’m using the following versions :

  • python = 3.6.1
  • matplotlib = 1.5.3
  • ffmpeg = N-82225-gb4e9252
  • OS = Windows 10

  Please advise me if further information is needed as it’s the first time I’ve attempted to record an animated plot.

  How do I adjust the aspect and resolution to work with the figure itself so nothing is cut off in the video ?