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• openCV save frames from RTSP non blocking

  1er janvier 2020, par Jacob nighFor

  I am building an app that records frames from IP camera through RTSP.

  My engine is in charge to save a video in mp4 with Opencv VideoWriter working well.
  What I am looking for is to create a startRecord and a stopRecord class method that will respectively start and stop recording according to a trigger (it could be an argument that I pass to the thread).
  Is anyone know what the best way to do that kind of stuff ?

  Here is my class :

  from threading import Thread
  
  import cv2
  
  import time
  
  import multiprocessing
  
  import threading
  
  class RTSPVideoWriterObject(object):
  
      def __init__(self, src=0):
  
          # Create a VideoCapture object
  
          self.capture = cv2.VideoCapture(src)
  
  
  
          # Start the thread to read frames from the video stream
  
          self.thread = Thread(target=self.update, args=())
  
          self.thread.daemon = True
  
          self.thread.start()
  
  
  
      def update(self):
  
          # Read the next frame from the stream in a different thread
  
          while True:
  
              if self.capture.isOpened():
  
                  (self.status, self.frame) = self.capture.read()
  
  
  
      def endRecord(self):
  
          self.capture.release()
  
          self.output_video.release()
  
          exit(1)
  
  
  
      def startRecord(self,endRec):
  
  
  
          self.frame_width = int(self.capture.get(3))
  
          self.frame_height = int(self.capture.get(4))
  
          self.codec = cv2.VideoWriter_fourcc(*'mp4v')
  
          self.output_video = cv2.VideoWriter('fileOutput.mp4', self.codec, 30, (self.frame_width, self.frame_height))
  
          while True:          
  
              try:
  
                  self.output_video.write(self.frame)
  
                  if endRec:
  
                      self.endRecord()
  
              except AttributeError:
  
                  pass
  
  
  
  
  
  
  
  
  
  if __name__ == '__main__':
  
  
  
      rtsp_stream_link = 'rtsp://foo:192.5545....'
  
      video_stream_widget = RTSPVideoWriterObject(rtsp_stream_link)
  
  
  
      stop_threads = False
  
      t1 = threading.Thread(target = video_stream_widget.startRecord, args =[stop_threads]) 
  
      t1.start() 
  
      time.sleep(15)
  
      stop_threads = True

  As you can see in the main I reading frames and store them in a separate thread. Then I am starting to record (record method is with an infinite loop so blocking) and then after 15 sec, I am trying to pass a ’stop_record’ argument to stop recording properly.

  A part of the code comes from Storing RTSP stream as video file with OpenCV VideoWriter

  Is someone have an idea ?
  I read a lot that OpenCV can be very tricky for multithreading

  N.

• What is a correct way of ffmpeg dshow webcamera properties save and load ?

  12 juin 2020, par C0oo1D

  Command (PS == Windows PowerShell) :

  



  PS D:\> ffmpeg -f dshow -show_video_device_dialog True -video_device_save some_profile.txt -i 'video=MicrosoftR LifeCam Studio(TM)'


  



  FFmpeg Header :

  



  ffmpeg version git-2020-06-04-7f81785 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9.3.1 (GCC) 20200523
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libsrt --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --disable-w32threads --enable-libmfx --enable-ffnvcodec --enable-cuda-llvm --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf
  libavutil      56. 49.100 / 56. 49.100
  libavcodec     58. 90.100 / 58. 90.100
  libavformat    58. 44.100 / 58. 44.100
  libavdevice    58.  9.103 / 58.  9.103
  libavfilter     7. 84.100 /  7. 84.100
  libswscale      5.  6.101 /  5.  6.101
  libswresample   3.  6.100 /  3.  6.100
  libpostproc    55.  6.100 / 55.  6.100


  



  Error after OK/Cancel/Close in camera settings dialog (empty file was created). Also tried without dialog - the same problem :

  



  [dshow @ 0715de40] Query for IPersistStream failed.
video=Microsoft® LifeCam Studio(TM): I/O error


  



  I assume that problem at the camera side, but I don't exclude my blindness (didn’t find any examples of saving settings or required command options in the documentation).

  



  Perhaps there is another way to save / load webcamera properties ?

  


• lavr : only save/restore the mixing matrix if mixing is being done

  30 novembre 2012, par Justin Ruggles

  lavr : only save/restore the mixing matrix if mixing is being done