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• FFmpeg extracts different number of frames when using -filter_complex together with the split filter

  14 juin 2016, par Konstantin

  I am fiddling with ffmpeg, extracting jpg pictures from videos. I am splitting the input stream into two output stream with -filter_complex, because I process my videos from direct http link (scarce free space on VPS), and I don’t want to read through the whole video twice (traffic quota is also scarce). Furthermore I need two series of pitcures, one for applying some filters (fps changing, scale, unsharp, crop, scale) and then selecting from them by naked eye, and the other series being untouched (expect fps changing, and cropping the black borders), using them for furter processing after selecting from the first series. I call my ffmpeg command from Ruby script, so it contains some string interpolation / substitution in the form #{}. My working command line looked like :

  ffmpeg -y -fflags +genpts -loglevel verbose -i #{url} -filter_complex "[0:v]fps=fps=#{new_fps.round(5).to_s},split=2[in1][in2];[in1]crop=iw-#{crop[0]+crop[2]}:ih-#{crop[1]+crop[3]}:#{crop[0]}:#{crop[1]},scale=#{thumb_width}:-1:flags=lanczos,unsharp,lutyuv=y=gammaval(#{gammaval})[out1];[in2]crop=iw-#{crop[0]+crop[2]}:ih-#{crop[1]+crop[3]}:#{crop[0]}:#{crop[1]}[out2]" -f #{format} -c copy #{options} -map_chapters -1 - -map '[out1]' -f image2 -q 1 %06d.jpg -map '[out2]' -f image2 -q 1 big_%06d.jpg

  #options is set when output is MP4, then its value is "-movflags frag_keyframe+empty_moov" so I can send it to standard output without seeking capability and uploading the stream somewhere without making huge temporary video files.
  So I get two series of pictures, one of them is filtered, sharpened, the other is in fact untouched. And I also get an output stream of the video on the standard output which is handled by Open3.popen3 library connecting the output stream of the input of two other commands.

  Problem arise when I would like to seek in the video to a given point and omitting the streamed video output on the STDOUT. I try to apply combined seeking, fast seek before the given time code and the slow seek to the exact time code, given in floating seconds :

  ffmpeg -report -y -fflags +genpts -loglevel verbose -ss #{(seek_to-seek_before).to_s} -i #{url} -ss #{seek_before.to_s} -t #{t_duration.to_s} -filter_complex "[0:v]fps=fps=#{pics_per_sec},split=2[in1][in2];[in1]crop=iw-#{crop[0]+crop[2]}:ih-#{crop[1]+crop[3]}:#{crop[0]}:#{crop[1]},scale=#{thumb_width}:-1:flags=lanczos,unsharp,lutyuv=y=gammaval(#{gammaval})[out1];[in2]crop=iw-#{crop[0]+crop[2]}:ih-#{crop[1]+crop[3]}:#{crop[0]}:#{crop[1]}[out2]" -map '[out1]' -f image2 -q 1  %06d.jpg -map '[out2]' -f image2 -q 1  big_%06d.jpg

  Running this command I get the needed two series of pictures, but they contains different number of images, 233 vs. 484.

  Actual values can be read from this interpolated / substituted command line :

  ffmpeg -report -y -fflags +genpts -loglevel verbose -ss 1619.0443599999999 -i fabf.avi -ss 50.0 -t 46.505879999999934 -filter_complex "[0:v]fps=fps=5,split=2[in1][in2];[in1]crop=iw-0:ih-0:0:0,scale=280:-1:flags=lanczos,unsharp,lutyuv=y=gammaval(0.526316)[out1];[in2]crop=iw-0:ih-0:0:0[out2]" -map '[out1]' -f image2 -q 1  %06d.jpg -map '[out2]' -f image2 -q 1  big_%06d.jpg

  Detailed log can be found here : http://www.filefactory.com/file/1yih17k2hrmp/ffmpeg-20160610-223820.txt
  Before last line it shows 188 duplicated frames.

  I also tried passing "-vsync 0" option, but didn’t help. When I generate the two series of images in two consecutive steps, with two different command lines, then no problem arises, I get same amount of pictures in both series of course. So my question would be, how can I use the later command line, generating the two series of images by only one reading / parsing of the remote video file ?

• Invalid buffer size, packet size 1447 expected frame_size 460800

  24 février 2017, par Thiruvarangan Vedantham

  I am trying to display raw video being captured from a capturing device using ffplay. The following command works fine :

  ’ffplay -fs -i /dev/video1’

  However, I need to rename the capture device to ’webcam’ and have added necessary UDEV rules and then trying to play using the following command :

  ’ffplay -s cif -pix_fmt yuv420p -f rawvideo /dev/webcam’

  This command gives me the following error :

  Invalid buffer size, packet size 1447 < expected frame_size 460800.
  Also tried :

  ’ffplay -fs -i /dev/web-cam’

  which gives me the following error :

  Invalid data found when processing input. Please help.

  Thanks in advance.

• doc/filters : re-edit notes on filtergraph escaping

  24 janvier 2014, par Stefano Sabatini

  doc/filters : re-edit notes on filtergraph escaping
  State the escaping rules more explicitly, reword various sentences and
  
  drop confusing quoting example.
  Should fix trac issue #3334.
  

  • [DH] doc/filters.texi