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• Webcam streaming from Mac using FFmpeg

  22 juillet 2016, par Galaxy

  I want to stream my webcam from Mac using FFmpeg.

  First I checked the supported devices using ffmpeg -f avfoundation -list_devices true -i ""

  Output :

  [AVFoundation input device @ 0x7fdf1bd03000] AVFoundation video devices:
  
  [AVFoundation input device @ 0x7fdf1bd03000] [0] USB 2.0 Camera #2
  
  [AVFoundation input device @ 0x7fdf1bd03000] [1] FaceTime HD Camera
  
  [AVFoundation input device @ 0x7fdf1bd03000] [2] Capture screen 0
  
  [AVFoundation input device @ 0x7fdf1bd03000] [3] Capture screen 1
  
  [AVFoundation input device @ 0x7fdf1bd03000] AVFoundation audio devices:
  
  [AVFoundation input device @ 0x7fdf1bd03000] [0] Built-in Microphone

  The device[0] is the webcam I want to use.

  ---

  Then I tried to capture the webcam using ffmpeg -f avfoundation -i "0" out.mpg

  Output :

  [avfoundation @ 0x7fe7f3810600] Selected framerate (29.970030) is not supported by the device
  
  [avfoundation @ 0x7fe7f3810600] Supported modes:
  
  [avfoundation @ 0x7fe7f3810600]   320x240@[120.101366 120.101366]fps
  
  [avfoundation @ 0x7fe7f3810600]   640x480@[120.101366 120.101366]fps
  
  [avfoundation @ 0x7fe7f3810600]   800x600@[60.000240 60.000240]fps
  
  [avfoundation @ 0x7fe7f3810600]   1024x768@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7fe7f3810600]   1280x720@[60.000240 60.000240]fps
  
  [avfoundation @ 0x7fe7f3810600]   1280x1024@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7fe7f3810600]   1920x1080@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7fe7f3810600]   320x240@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7fe7f3810600]   640x480@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7fe7f3810600]   800x600@[20.000000 20.000000]fps
  
  [avfoundation @ 0x7fe7f3810600]   1024x768@[6.000002 6.000002]fps
  
  0: Input/output error

  ---

  After that, I tried stream this webcam from my Mac using ffmpeg -f avfoundation -framerate 30 -i "0" -f mpeg1video -b 200k -r 30 -vf scale=1920:1080 http://127.0.0.1:8082/

  Output :

  [avfoundation @ 0x7f8515012800] An error occurred: The activeVideoMinFrameDuration passed is not supported by the device.  Use -activeFormat.videoSupportedFrameRateRanges to discover valid ranges.0: Input/output error

  ---

  I cannot capture or stream this webcam. However when I used the Facetime camera instead of this webcam, everything was OK. I’ve been searching for this problem for a few days, but still cannot fix it. Does anyone have experience with webcam and FFmpeg on Mac ?

• ffmpeg get frame time stamp

  19 novembre 2018, par Anshul G.

  I am trying to record a webcam video using ffmpeg. I have a logitech c922 Pro Stream Webcam. This is the command that I use :

  ffmpeg -f v4l2 -framerate 60 -video_size 1280x720 -input_format mjpeg -i /dev/video1 out.mp4

  My application requires me to get the exact timestamp for every frame. While I could use my knowledge of the framerate and frame number to add the required interval to the start time, I am afraid that this might not be completely accurate.

  Firstly, I have noticed that while recording, the console seems to initially display a far higher fps than the one I have set :

  Press [q] to stop, [?] for help
  
  frame=  177 fps= 85 q=-1.0 Lsize=     502kB time=00:00:02.91 bitrate=1410.8kbits/s dup=144 drop=0    

  Also, I think that ffmpeg drops frames in between sometimes.

  However, my videos seem to have the correct number of frames so I think that the fps value displayed could instead be referring to the encoding/ decoding speed. I am not sure about frame dropping.

  I would be happy of you could let me know what you think, or suggest an alternative so that I can timestamp my frames accurately. Thanks !

  Edit :

  I have understood that frame rate is correlated to ambient light which can lead to high duplication in frames. I am currently recording on windows and have set frame rate as the priority in logitech gaming software. However there is still the occasional drop in frame or duplication. Does this affect time stamp of the frames ? Or can I extrapolate from the start time ?

• avfoundation error. Cannot detect list_devices

  12 septembre 2016, par xiaose

  I need to get ID for current screen and, as it said here, I tried to get list of all available input devices...

  Whith command ffmpeg -f avfoundation -list_devices true -i ''

  It works fine on two my Mac but on the third, with OSX 10.7.5 it does not works :

  $ ./ffmpeg -f avfoundation -list_devices true -i ''
  
  ffmpeg version 3.1.1 Copyright (c) 2000-2016 the FFmpeg developers
  
  ...
  
  Unrecognized option 'list_devices'.

  I got

  Unrecognized option ’list_devices’

  there and don’t know how to fix it. Could you help me with that ?

  Like I understand this situation, there is issue with avfoundation. It just doesn’t works correctly...

  From another side it gives me error :

  Unknown format ’avfoundation’

  $ ./ffmpeg -h demuxer=avfoundation
  
  ffmpeg version 3.1.1 Copyright (c) 2000-2016 the FFmpeg developers
  
  ...
  
  Unknown format 'avfoundation'.

  UPD : issue was in ffmpeg. That version what I used just does not support interaction with avfoundation