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• How to grab laptop webcam video with ffmpeg in windows

  25 août 2018, par Ofer Sadan

  I have a small python program that works very well to capture short videos from webcams in linux (at least for laptops that have built-in webcams) using a sub-process with ffmpeg.

  Now i’m trying to write the same program to capture webcams in windows, and i know i can’t use the generic "/dev/video0" that works pretty well in linux, but i thought something like naming it "Integrated Camera" should be enough, but it fails.

  Here’s my linux code (that works) :

      import sys
  
      from subprocess import call
  
      from datetime import datetime
  
      def record_webcam(seconds):
  
          cam = '/dev/video0'
  
          timestamp = datetime.now().strftime('%Y%m%d-%H%M%S')
  
          filename = timestamp + 'something.mkv' #generated with more complexity in the actual code, but that isn't important
  
          ffmpeg_cmd = 'ffmpeg -t {} -an -i {} -c:v libx264 -preset veryslow -crf 25 {}'.format(seconds, cam, filename).split()
  
          p = call(ffmpeg_cmd)
  
          return filename if p == 0 else False
  
  
  
      if __name__ == '__main__':
  
          record_webcam(sys.argv[1])

  I have looked at the documentation for ffmpeg and tried to search for solution but so far i’m lost...

  I know that "Integrated Camera"s are only available on some laptops and not others, and that it won’t capture other cameras connected, but it’s enough for my use case... but if you want a challenge I would also like to know how to apply it to any windows-pc with a camera regardless of what it’s called.

  Also, is it easier or more recommended to do what i’m trying here only with python tools, like OpenCV ?

  Thanks in advance !
  Edit : I answered my own question with a partial solution if anyone is interested based on a comment from @Mulvya, but if anyone can still explain to me the part about OpenCV I would still like to hear it...

  Follow up question here : ffmpeg through python subprocess fails to find camera

• rtp : rfc4175 : add handler for YCbCr-4:2:2

  31 mars 2017, par Damien Riegel

  rtp : rfc4175 : add handler for YCbCr-4:2:2
  This adds partial support for the RFC 4175 (raw video over RTP). The
  
  only supported formats are the YCbCr-4:2:2 8 bit because it’s natively
  
  supported by FFmpeg with pixel format UYVY, and 10 bit which requires
  
  the vrawdepay codec to convert the payload in a format handled by
  
  FFmpeg.
  Signed-off-by : Damien Riegel <damien.riegel@savoirfairelinux.com>
  
  Reviewed-by : Rostislav Pehlivanov <atomnuker@gmail.com>
  

  • [DH] libavformat/Makefile
  • [DH] libavformat/rtpdec.c
  • [DH] libavformat/rtpdec_formats.h
  • [DH] libavformat/rtpdec_rfc4175.c

• Use ffmpeg to downscale, tonemap, downmix and re encode mkv

  1er février 2021, par nikartz

  I try to use ffmpeg to downscale a 4k and tonemap a 4k HDR mkv to a 1080p SDR mkv with this code :

  


  ffmpeg -i "Input.mkv" -vf zscale=t=linear:npl=100,format=gbrpf32le,zscale=p=bt709,tonemap=tonemap=hable:desat=0,zscale=t=bt709:m=bt709:r=tv,format=yuv420p -c:v hevc_nvenc -b:v 12M -preset slow "Output.mkv"


  


  The problem is, that only the first audio track (of four) is copied to the new mkv and the subtitle tracks are missing :

  


  Input :

  


  Stream #0:0: Video: hevc (Main 10), yuv420p10le(tv, bt2020nc/bt2020/smpte2084), 3840x2160 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn, 23.98 tbc (default)
Stream #0:1(ger): Audio: eac3, 48000 Hz, 7.1, fltp (default)
Stream #0:2(ger): Audio: dts (DTS-HD MA), 48000 Hz, 7.1, s16p
Stream #0:3(eng): Audio: truehd, 48000 Hz, 7.1, s32 (24 bit)
Stream #0:4(eng): Audio: ac3, 48000 Hz, 5.1(side), fltp, 640 kb/s
Stream #0:5(ger): Subtitle: subrip (default) (forced)
Stream #0:6(ger): Subtitle: dvd_subtitle, 1920x1080 (forced)
Stream #0:7(ger): Subtitle: hdmv_pgs_subtitle, 1920x1080 (forced)
Stream #0:8(ger): Subtitle: dvd_subtitle, 1920x1080
Stream #0:9(ger): Subtitle: hdmv_pgs_subtitle
Stream #0:10(eng): Subtitle: dvd_subtitle, 1920x1080
Stream #0:11(eng): Subtitle: hdmv_pgs_subtitle


  


  Output :

  


  Stream #0:0: Video: hevc (Main), yuv420p(tv), 3840x2160 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn, 23.98 tbc (default)
Stream #0:1(ger): Audio: vorbis, 48000 Hz, 7.1, fltp (default)
Stream #0:2(ger): Subtitle: ass (default) (forced)


  


  I would like to have an mkv as output converts all the audio tracks to aac Stereo (but keeps all four of them), copies the subtitle tracks and tonemaps/downscales the video track.

  


  I have tried to use the -map 0 or -map 0:a:0 -map 0:a:1 ... commands (and some similiar to those, however I seemingly end up with either one audio track, no video track or a video track that is just copied.

  


  I possible, I would also like to use nvenc with a high quality preset, which is the reason for -c:v hevc_nvenc -b:v 12M -preset slow in my command, however I have no idea, if this is done right, since the ouput mkv also as a 4k video track instead of a 1080p. Maybe this is caused by the -c:v because it overrides -vf ? Sorry, I am feeling dumb and am just getting started with ffmpeg.

  


  There is so much information about ffmpeg out there, but it is either too complicated for me, or not answering my questions.

  


  Thanks for your help !