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• mplayer or ffmpeg to display video that is beeing pushed to the player ?

  18 décembre 2020, par Sebastian Heyn

  I am planning an application, where an outside video camera should be displayed using mplayer (or any other lightweight video player).

  


  However, instead of connecting the mplayer to the camera server (ffmpeg or something), I want the camera to push the video to the player.

  


  The camera will be on an unstable network, and it will be natted so I cannot access without using a VPN or ssh tunnel. Those tunnels will consume CPU power, bandwidth and connection establish time.

  


  Ideally, the last received frame will be displayed, until the next frame is received, without closing the window.

  


  Does anyone know a way to achieve this using existing software ? BTW : The camera will be connected to a raspberry or simillar.

  


• stream usb webcam via http using vlc without transcoding using mjpeg signal from webcam

  10 novembre 2020, par Peter Nußreiner

  I wanna stream my (Microsoft live) USB webcam using vlc from a raspberry.
While it works perfectely fine with transcoding my raspberry does not have enough power.

  


  So I checked the output formats of my webcam using :

  


  ffmpeg -f v4l2 -list_formats all -i /dev/video0


  


  wich gives me the following output :

  


  [video4linux2,v4l2 @ 0x559d5aee36c0] Raw       :     yuyv422 :           YUYV 4:2:2 : 640x480 1280x720 960x544 800x448 640x360 424x240 352x288 320x240 800x600 176x144 160x120 1280x800
[video4linux2,v4l2 @ 0x559d5aee36c0] Compressed:       mjpeg :          Motion-JPEG : 640x480 1280x720 960x544 800x448 640x360 800x600 416x240 352x288 176x144 320x240 160x120
/dev/video0: Immediate exit requested


  


  when running my streaming command :

  


  cvlc v4l2:///dev/video0:chroma=h264:width=1280:height=720 --sout '#standard{access=http,mux=ts,dst=192.168.178.27:8080,name=stream,mime=video/ts}' -vvv


  


  I get the following error :

  


  mux_ts mux warning: rejecting stream with unsupported codec YUY2
main mux error: cannot add this stream
main decoder error: cannot create packetizer output (YUY2)


  


  along with many other lines of information.
As far as I can interpret the error, vlc wants to use the YUY2 RAW signal of my webcam.
Is there any way I can force vlc to use the mjpg output of my camera ?

  


  I've already tried to use 'chroma=mjpg' without success.
Transcoding is not an alternative as my raspi has by far not enough power.

  


  I've also read about using ffmpeg for streaming, maybe someone has an alternative solution since I'm very new to the whole topic of websites and stuff

  


  It will (or should) be used as a live webcam for a windsurfing spot.
Therefore I need a fluent video with at least 10fps to judge the situation. A delay of a minute or so is no problem.
The basic idea was to stream the video to a webserver and embed the image in a website. I've got good internet connection at the spot.

  


  But for now I want to try it locally on my pc.

  


• Input seeking for frame at specified timestamp with Py-AV

  9 décembre 2019, par neonScarecrow

  I have a project already using Py-AV and am trying to replicate a specific ffmpeg command. The goal is to get a frame roughly around the specified timestamp.

  Here’s the ffmpeg commmand :
  https://trac.ffmpeg.org/wiki/Seeking

  ffmpeg -ss 14 -i https://some_url.mp4 -frames:v 1 frame_at_14_seconds.jpg

  Here’s my code :

      #return one frame around 14 seconds into the movie
  
      target_sec = 14 
  
      container = av.open('https://some_url.mp4', 'r')
  
      container.streams.video[0].thread_type = 'AUTO'
  
      video_stream = next(s for s in container.streams if s.type == 'video')
  
      time_base = float(video_stream.time_base)
  
      target_timestamp = int(target_sec / time_base) + video_stream.start_time
  
      video_stream.seek(target_timestamp)
  
      for frame in container.decode(video_stream):
  
          frame.to_image().save('frame_at_14_seconds.jpg')
  
          break

  Additionally, I have found any documentation about this, but does anyone know if either command (ffmpeg/av.open) is downloading the entire file to a tmp file behind the scenes. I’m looking for a less memory-intensive way to read a frame for every second in an up to 60 second video.