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• Trouble with the ffmpeg -ss flag when capturing one frame from a Macbook iSight webcam

  1er mars 2014, par Andy

  For about five years I've used ffmpeg in a shell script to grab one frame from my linux'd-up Macbook's iSight :

  ffmpeg -f video4linux2 -s 640x480 -r 15 -i /dev/video0 -an -vframes 1 -vcodec mjpeg -y -sameq -ss 1.5 snapshot.jpg

  I just upgraded my Ubuntu distro from Lucid to Natty (ffmpeg ver. 0.6.2-4:0.6.2-1ubuntu1).
  Now that syntax turns the iSight on but hangs indefinitely.

  [output snipped, ending with:]
  
  frame=    0 fps=  0 q=0.0 Lsize=      -0kB time=10000000000.00 bitrate=  -0.0kbits/s    
  
  video:0kB audio:0kB global headers:0kB muxing overhead -inf%

  Without the '-ss' flag it seems to successfully grab the first frame and exit immediately - the only difference in output being :

  frame=    1 fps=  0 q=0.0 Lsize=      -0kB time=0.07 bitrate=  -2.6kbits/s    
  
  video:16kB audio:0kB global headers:0kB muxing overhead -100.132730%

  However, the '-ss 1.5' was necessary to delay the frame capture by 1.5 seconds to allow the cam sufficient time to adjust the exposure.

  The -itsoffset flag seemed promising, but doesn't seem to change ffmpeg's behavior (ie doesn't hang, but no delay).

  Any ideas ?

• Trouble with the ffmpeg -ss flag when capturing one frame from a Macbook iSight webcam

  31 août 2011, par Andy

  For about five years I've used ffmpeg in a shell script to grab one frame from my linux'd-up Macbook's iSight :

  ffmpeg -f video4linux2 -s 640x480 -r 15 -i /dev/video0 -an -vframes 1 -vcodec mjpeg -y -sameq -ss 1.5 snapshot.jpg

  I just upgraded my Ubuntu distro from Lucid to Natty (ffmpeg ver. 0.6.2-4:0.6.2-1ubuntu1).
  Now that syntax turns the iSight on but hangs indefinitely.

  [output snipped, ending with:]
  
  frame=    0 fps=  0 q=0.0 Lsize=      -0kB time=10000000000.00 bitrate=  -0.0kbits/s    
  
  video:0kB audio:0kB global headers:0kB muxing overhead -inf%

  Without the '-ss' flag it seems to successfully grab the first frame and exit immediately - the only difference in output being :

  frame=    1 fps=  0 q=0.0 Lsize=      -0kB time=0.07 bitrate=  -2.6kbits/s    
  
  video:16kB audio:0kB global headers:0kB muxing overhead -100.132730%

  However, the '-ss 1.5' was necessary to delay the frame capture by 1.5 seconds to allow the cam sufficient time to adjust the exposure.

  The -itsoffset flag seemed promising, but doesn't seem to change ffmpeg's behavior (ie doesn't hang, but no delay).

  Any ideas ?

• 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