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• Streaming webcam from ffmpeg to Electron app

  28 mars 2017, par potatoes

  I’m working on a prototype application that consists of an Electron app that talks to a local Flask-based Python service (both on the same machine). On the electron app I want to have a "start" button that has starts to record the machine’s desktop (screencast). I do this by using ffmpeg at the Python backend. In a python subprocess I issue the following command :

  ffmpeg -f gdigrab -framerate 30 -i desktop `outputFile`

  Similarly, I’m able to record the webcam with ffmpeg as follows :

  ffmpeg -f dshow -i video="Integrated Webcam" `outputFile`

  However, I want to be able to stream the webcam to the electron app while recording simultaneously. This is to show a "screencasting" experience at the electron end. So basically my question boils down to streaming to an html5 video element while simultaneously recroding it in ffmpeg. I’ve searched for a way to do so and this page suggest that I can do it over a VLC streaming server locally ? I found a few links but I’m not sure whether I should be starting some kind of RTP server locally and streaming the webcam from ffmpeg to that server which will distribute the stream ? I’m confused about what is needed to make this happen, and any pointers are appretiated ! Thanks !

• avdevice/xcbgrab : don't assume xserver endianness

  31 janvier 2021, par Andriy Gelman

  avdevice/xcbgrab : don't assume xserver endianness
  xserver defines the endianness of the grabbed images. Use this information
  
  to set the correct pixel format.
  This also fixes format selection in configuration depth=32/bpp=32 with
  
  xserver on a little endian machine. Before the patch, the big endian
  
  layout 0RGB was always selected which is incorrect because BGR0 should
  
  be used. RGB24 was also incorrectly assumed (but this format was removed
  
  in xserver 1.20).
  The big-endian settings can be tested using docker+qemu from a little-endian
  
  machine :
  $ docker run —rm —privileged multiarch/qemu-user-static —reset -p yes
  
  $ docker run —rm -it -v /tmp :/tmp powerpc64/debian /bin/bash
  In docker container
  
  $ apt-get update
  
  $ apt-get install xvfb
  
  $ apt-get install x11-apps
  To test AV_PIX_FMT_0RGB32
  
  $ Xvfb :2 -screen 0 720x480x24 &
  
  $ export DISPLAY=:2
  
  $ xclock -geometry 720x480 -bg green #test different colors
  On your host machine grab the frames using the following
  
  command. View output to check that colors are rendered correctly
  
  $ ./ffmpeg -y -f x11grab -i :2.0 -codec:v mpeg2video out.mp4
  Other pixel formats can be tested by modifying how Xvfb is started in the docker
  
  container :
  AV_PIX_FMT_RGB565
  
  $ Xvfb :2 -screen 0 720x480x16
  AV_PIX_FMT_RGB555
  
  $ Xvfb :2 -screen 0 720x480x15
  AV_PIX_FMT_BGR24 / AV_PIX_FMT_RGB24
  
  This is difficult to test because bpp=24 support was removed in xserver 1.20
  
  https://lists.x.org/archives/xorg-devel/2018-February/056175.html?hmsr=joyk.com&utm_source=joyk.com&utm_medium=referral
  
  However, I was able to run previous version of Xvfb (with some
  
  modifications to force 24bpp) to check that images are rendered correctly.
  Reviewed-by : Carl Eugen Hoyos <ceffmpeg@gmail.com>
  
  Signed-off-by : Andriy Gelman <andriy.gelman@gmail.com>
  

  • [DH] libavdevice/xcbgrab.c

• Webcam - Publishing and Archiving on line video files

  11 novembre 2014, par Emmanuel Brunet

  I want to publish an ASF live video stream over the internet and also copy the backup to disk (without sound to spare disk space)

  I’m running debian 7.7 wheezy / ffmpeg 2.2 and ffserver 1.2.9.

  ---

  The IP camera video streams specifications are

  Input #0, asf, from 'http://account:password@webcam/videostream.asf':
  
    Duration: N/A, start: 0.000000, bitrate: 32 kb/s
  
      Stream #0:0: Video: mjpeg (MJPG / 0x47504A4D), yuvj422p(pc), 640x480, 50 tbr, 1k tbn, 1k tbc
  
      Stream #0:1: Audio: adpcm_ima_wav ([17][0][0][0] / 0x0011), 8000 Hz, 1 channels, s16p, 32 kb/s

  To achieve this I have set up a /etc/ffserver.conf configuration

  Port 11000
  
  
  
  BindAddress 0.0.0.0
  
  
  
  MaxClients 1000
  
  
  
  MaxBandwidth 40000
  
  
  
  CustomLog -
  
  
  
  <feed>
  
  File /tmp/feed1.ffm
  
  FileMaxSize 200K
  
  ACL allow localhost
  
  ACL allow 192.168.1.1 192.168.255.255
  
  
  
  </feed>
  
  
  
  
  
  # --------------------------- ASF ----------------------
  
  
  
  <stream>
  
  Feed feed1.ffm
  
  Format asf
  
  
  
  AVOptionVideo flags +global_header
  
  VideoFrameRate 25
  
  VideoSize 640x480
  
  VideoBitRate 1024
  
  VideoBufferSize 1024
  
  StartSendOnKey
  
  NoAudio
  
  </stream>
  
  
  
  # ------------ Server status -------------------
  
  
  
  <stream>
  
  Format status
  
  
  
  # Only allow local people to get the status
  
  ACL allow localhost
  
  ACL allow 192.168.0.0 192.168.255.255
  
  
  
  #FaviconURL http://pond1.gladstonefamily.net:8080/favicon.ico
  
  </stream>
  
  
  
  
  
  # ---------- Redirect --------------------
  
  
  
  <redirect>
  
  URL http://www.ffmpeg.org/
  
  </redirect>

  To connect the feed I run

  to start the ffserver

  ffserver -f /etc/ffserver.conf

  to collect the stream from the camera

  ffmpeg -i http://account:password@webcam/videostream.asf -c:v libx264 -an http://localhost:11000/feed1.ffm

  and all works like a charm.

  ---

  My questions are :

  • How in the same time having the stream saved to disk ?

  (as done by the command)

  ffmpeg -i http://account:password@webcam/videostream.asf -preset veryfast -t 00:60:00 -b:v 512K -c:v libx264 -pix_fmt yuv420p -an /var/backup/videos/YYY-MM-DD.mp4

  Note that the output .mp4 file names should rotate to get multiple timestamped output archives

  • How can I published video over RTSP ?

  I’ve found examples on the internet but none worked for me

  Thanks in advance

  regards