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• Recording RTSP steam with Python

  6 mai 2022, par ロジャー

  Currently I am using MediaPipe with Python to monitor RTSP steam from my camera, working as a security camera. Whenever the MediaPipe holistic model detects humans, the script writes the frame to a file.

  


  i.e.

  


  # cv2.VideoCapture(RTSP)
# read frame
# while mediapipe detect
#   cv2.VideoWriter write frame
# store file


  


  Recently I want to add audio recording support. I have done some research that it is not possible to record audio with OpenCV. It has to be done with FFMPEG or PyAudio.

  


  I am facing these difficulities.

  


  


  1. When a person walk through in front of the camera, it takes maybe less than 2 seconds. For the RTSP stream being read by OpenCV, human is detected with MediaPipe, and start FFMPEG for recording, that human should have walked far far away already. So FFMPEG method seems not working for me.

     


  


  2. For PyAudio method I am currently studying, I need to create 2 threads establishing individual RTSP connections. One thread is for video to be read by OpenCV and MediaPipe. The other thread is for audio to be recorded when the OpenCV thread notice human is detected. I have tried using several devices to read the RTSP streams. The devices are showing timestamps (watermark on the video) with several seconds in difference. So I doubt if I can get video from OpenCV and audio from PyAudio in sync when merging them into one single video.

     


  


  


  Is there any suggestion how to solve this problem ?

  


  Thanks.

  


• Imagemagick & Pillow generate malformed GIF frames

  1er juin 2016, par RiTu

  I need to extract the middle frame of a gif animation.

  Imagemagick :

  convert C:\temp\orig.gif -coalesce C:\temp\frame.jpg

  generates the frames properly :

  

  However when I extract a single frame :

  convert C:\temp\orig.gif[4] -coalesce C:\temp\frame.jpg

  then the frame is malformed, as if the -coalesce option was ignored :

  

  Extraction of individual frames with Pillow and ffmpeg also results in malformed frames, tested on a couple of gifs.

  Download gif : https://i.imgur.com/Aus8JpT.gif

  I need to be able to extract middle frames of every gif version in either PIL, Imagemagick of ffmpeg (ideally PIL).

• libavformat : Improve ff_configure_buffers_for_index for excessive deltas

  21 mars 2023, par Martin Storsjö

  libavformat : Improve ff_configure_buffers_for_index for excessive deltas
  Previously, the ff_configure_buffers_for_index function had
  
  upper sanity limits of 16 MB (1<<24) for buffer_size and
  
  8 MB (1<<23) for short_seek_threshold.
  However, if the index contained entries with a much larger
  
  delta, setting pos_delta to a value larger than the sanity
  
  limit, we would end up not increasing the buffer size at all.
  Instead, ignore the individual deltas that are excessive, but
  
  increase the buffer size based on the deltas that are below the
  
  sanity limit.
  Only count deltas that are below 1<<23, 8 MB ; pos_delta gets doubled
  
  before setting the buffer size - this matches the previous maximum
  
  buffer size of 1<<24, 16 MB.
  This can happen e.g. with a mov file with some tracks containing
  
  some samples that belong in the start of the file, at the end of
  
  the mdat, while the rest of the file is mostly reasonably interleaved ;
  
  previously those samples caused the maximum pos_delta to skyrocket,
  
  skipping any buffer size enlargement.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavformat/seek.c