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• Sync a video stream at two separate receivers

  2 septembre 2019, par Quasar

  I want to use two separate receivers which both are receiving the same video stream. One of the receivers does some processing tasks and pass the results to the other receiver (using web-socket or a RESTFUL API) so that the second receiver displays the results and play the video(the frames and result values should be synchronized in the second receiver). The actual issue is how to synchronize these receivers over the IP network.
  Note that it is highly preferred that each one can read the stream by its own and I want to prevent resending the stream to the other receiver. A possible solution can be extracting timestamp in both receivers but I am not sure if it is possible. Can anyone help me how I can find a good solution for this ? Thanks in advance.

• openCV image Stitching wide angle 160 degrees

  4 janvier 2020, par a.masri

  I’m trying to Stitching image wide angle 160.5 degree but the result is not a good

  i’m using OpenCV 4 and ffmpeg to get frames from video

  ffmpeg command to get 15 frame per sec :

  ffmpeg -i first.mp4 -vf fps=15  preview%05d.jpg

  OpenCV Stitching code

  import cv2
  
  import numpy as np
  
  
  
  images = []
  
  for i in range(70):
  
      name = ('preview%05d.jpg' % (i+1))
  
      print(name)
  
      images.append(cv2.imread(name , cv2.IMREAD_COLOR))
  
  
  
  
  
  print("start ")
  
  stitcher = cv2.Stitcher_create()
  
  ret, pano = stitcher.stitch(images)
  
  
  
  if ret == cv2.STITCHER_OK:
  
      cv2.imshow('panorama', pano)
  
      cv2.waitKey()
  
      cv2.destroyAllWindows()
  
  else:
  
      print(cv2.STITCHER_ERR_NEED_MORE_IMGS)
  
      print(cv2.STITCHER_ERR_HOMOGRAPHY_EST_FAIL)
  
      print(cv2.STITCHER_ERR_CAMERA_PARAMS_ADJUST_FAIL)
  
      print(ret)
  
      print('Error during stiching')

  actual result :

  

  expected result :

  

• How do I capture all keyframes and scale down to 320px wide ?

  6 janvier 2020, par DwarfMacmillan

  I’m trying to use ffmpeg to output all key-frames from a video file and scale them down to 320px wide while maintaining aspect ratio.
  I know I could do this with two separate commands but I am trying to find a way to do it tidily in one.

  I’ve already succeeded in each of the steps individually using the following commands.

  Output the keyframes :

  .\ffmpeg -i input.mp4 -q:v 2 -vf select="eq(pict_type\,PICT_TYPE_I)" -vsync 0 thumb%07d.png

  Scale images :

  .\ffmpeg -i input.mp4 -vf scale=320:-1 thumb%07d.png

  I won’t share everything i’ve tried, but here’s three failures at combining them.

  //fail, not just keyframes, scaled
  .\ffmpeg -i input.mp4  -q:v 2 -vf select="eq(pict_type\,PICT_TYPE_I)" -vsync 0 -vf scale=320:-1 thumb%07d.png -hide_banner

  //fail, can’t find suitable output format for scale command, invalid argument
  .\ffmpeg -i input.mp4  -q:v 2 -vf select="eq(pict_type\,PICT_TYPE_I)" -vsync 0, scale=320:-1 thumb%07d.png -hide_banner

  //fail
  .\ffmpeg -i input.mp4 -q:v 2 -vf scale=320:-1, -vf select="eq(pict_type\,PICT_TYPE_I)" -vsync 0 thumb%07d.png -hide_banner

  I’ve tried many different things, moving commands, combining using commas etc... But I have not had any success at combining the get key-frames and scale commands.
  So how would I go about combining the get key-frames and scale commands so that it works ?

  thanks.