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• Generate individual HLS-compatible .ts segments on-demand by downloading as little bytes as possible from a remote input file

  27 janvier 2017, par Romain Cointepas

  I’m trying to generate individual HLS-compatible .ts segments on-demand by downloading/reading as little bytes as possible from a remote input file (hosted on a server supporting byte-ranges requests).

  One of the application for this would be to be able to transcode and play on Apple TV (via Airplay) a remote file that is not Airplay compatible, without having to download the entire file first.

  I am generating the playlist myself, and I have access to the ffprobe results for the remote file (that gives video duration, etc.).

  I have something working that plays via Airplay but with small video and audio glitches between each segments when I use the following command to generate each segment :

  ffmpeg -ss 60 -t 6 -i http://s3.amazonaws.com/misc-12345/avicii.vob -f mpegts -map 0:v:0 -map 0:a:0 -c:v libx264 -bsf:v h264_mp4toannexb -force_key_frames "expr:gte(t,n_forced*6)" -forced-idr 1 -pix_fmt yuv420p -colorspace bt709 -c:a aac -async 1 -preset ultrafast pipe:1

  Note : above command is for segment 11.ts, and in the m3u8 playlist I advertise each segment duration as 6 seconds.

  Here is a Youtube video showing the audio/video glitches between segments :
  https://www.youtube.com/watch?v=0vMwgbSfsu0

  The segment or hls modules of ffmpeg can’t be used because they both generate all the segments at once.

  I’ve been struggling on this for some days now and I would really appreciate some help !

• How to use v4l2 scrcpy virtual webcam ?

  2 mars 2024, par Emma bundy

  I created a virtual camera v4l2 /dev/video21 and linked it to my notebook's default webcam /dev/video1 and it started working so far ok, then I mirrored the webcam I created in OBS-studio.

  


  and now I want to connect in scrcpy the virtual camera that I created that is active /dev/video21, but I don't know how to do that, what commands to give to use the v4l2 /dev/video21 camera from the computer on my cell phone.

  


  which is already mirrored on the computer screen via wireless

  


  I need help, who can help me I thank you immensely ! This is for my college studies

  


  I tried to do this several times but I couldn't, I use Fedora 37 gnome, I used ffmpeg to link the webcam /dev/video1 + /dev/video21, and I mirrored it in OBS-studio, but I don't know which command to give to send the /dev/video21 video stream to my cell phone, use the virtual camera created on the cell phone.

  


• Saving frames from multiple videos in a specific location using openCV/ffmpeg and Python

  15 janvier 2019, par Sparkiepandas

  I am trying to extract and save the first frame from multiple videos in a specific folder. For now I got the extraction part working but my saving is in BGR instead of the preferred RGB (if I am right).Although, the frames are shown in my notebook as RGB but not as BGR. Also I need to add some variable filename,because at the moment it saves the frames but keeps overwriting the same frame. Can you guys help me with the two specific problems ? This is what I got so far :

  SOLVED : I got the saving working, output file and colouring

  img_rows,img_cols=200,200 
  
  
  
  listing = os.listdir(r'C:\Users/Me\SVWnew\archery\train')
  
  
  
  # Create a counter
  
  counter = 0
  
  for vid in listing:
  
      vid = r"C:/Users/Me/SVWnew/archery/train/"+vid
  
      cap = cv2.VideoCapture(vid)
  
  
  
      for k in range(1):
  
          ret, frame = cap.read()
  
          rgb =cv2.resize(frame,(img_rows,img_cols))
  
          plt.imshow(rgb)
  
          plt.xticks([]), plt.yticks([])  
  
          plt.show()
  
          pathOut = r"C:/Users/Me/SVWnew - Copy/archery/train"
  
          cv2.imwrite(pathOut + "/frame%d.jpg" % counter, rgb) 
  
          counter += 1
  
          if cv2.waitKey(1) & 0xFF == ord('q'):
  
              break
  
  
  
      cap.release()
  
      cv2.destroyAllWindows()