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• Need explanation of details of ffmpeg and pipes comand

  6 décembre 2011, par Don Nummer Jr

  Got the following from FFmpeg FAQ :

  mkfifo intermediate1.mpg
  
  mkfifo intermediate2.mpg
  
  ffmpeg -i input1.avi -sameq -y intermediate1.mpg < /dev/null &
  
  ffmpeg -i input2.avi -sameq -y intermediate2.mpg < /dev/null &
  
  cat intermediate1.mpg intermediate2.mpg |\
  
  ffmpeg -f mpeg -i - -sameq -vcodec mpeg4 -acodec libmp3lame output.avi

  Before i use or modify it I would like to understand it completely.

  What does the < /dev/null & do ?

  I understand | is pipe but why |\ ?

  What is the -f mpeg after ffmpeg (Seems, it tells ffmpeg to accept the piped in output from the cat(?) )

• Getting incorrect output resolution ffmpeg

  29 octobre 2011, par Adam

  I am capturing an RTSP stream from a security camera, and transcoding it for (live streaming) to iphone, using OSX as the encoding platform.
  I have it working correctly, and Im tuning it.
  However, it seems that it is not outputting the requested resolution. This is my script

  /Applications/SecurityCamera/openRTSP -v -c -t rtsp://10.0.1.118/ch1-s1 | \
  
      /Applications/SecurityCamera/ffmpeg \
  
      -r 10 -i - \
  
      -y -an -ab 64000 -f mpegts -vcodec copy -s 960x640 \
  
      -flags +loop -cmp +chroma -partitions +parti4x4+partp8x8+partb8x8 \
  
      -subq 5 -trellis 1 -refs 1 -coder 0 -me_range 16  -keyint_min 25 -sc_threshold 40 \
  
      -i_qfactor 0.71 -bt 400k -maxrate 524288 -bufsize 524288 \
  
      -qcomp 0.6 -qmin 10 -qmax 51 -qdiff 4 -level 30 \
  
      -aspect 960:640 -r 10 -g 10 -async 2 -\
  
      | /Applications/SecurityCamera/mediastreamsegmenter -b http://hydracam.dyndns.org:8080/ -f /Library/WebServer/Documents/ -i stream.m3u8 -t 10 -s 4 -D

  This is the status report :

  Input #0, h264, from 'pipe:':
  
  
  
    Duration: N/A, bitrate: N/A
  
    Stream #0.0: Video: h264, yuv420p, 1600x1200, 10 fps, 10 tbr, 1200k tbn, 20 tbc
  
    [mpegts @ 0x10100c200] muxrate VBR, pcr every 1 pkts, sdt every 200, pat/pmt every 40 pkts
  
    Output #0, mpegts, to 'pipe:':
  
    Metadata:
  
      encoder         : Lavf52.93.0
  
      Stream #0.0: Video: libx264, yuv420p, 1600x1200 [PAR 1:1 DAR 4:3], q=2-31, 90k tbn, 10 tbc
  
  Stream mapping:
  
    Stream #0.0 -> #0.0

  You can see that its working, but it is outputting 1600x1200 for some reason.

  If I change the -vcodec copy to -vcodec libx264 then I get the correct status report (stating 960x640, correct), but the streaming halts after 54 frames (see output below)

  Seems stream 0 codec frame rate differs from container frame rate: 20.00 (20/1) -> 10.00 (20/2)
  
  Input #0, h264, from 'pipe:':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0.0: Video: h264, yuv420p, 1600x1200, 10 fps, 10 tbr, 1200k tbn, 20 tbc
  
  [buffer @ 0x100d02420] w:1600 h:1200 pixfmt:yuv420p
  
  [scale @ 0x100d026f0] w:1600 h:1200 fmt:yuv420p -> w:960 h:640 fmt:yuv420p flags:0x4
  
  [libx264 @ 0x10100d400] using SAR=1/1
  
  [libx264 @ 0x10100d400] frame MB size (60x40) > level limit (1620)
  
  [libx264 @ 0x10100d400] using cpu capabilities: MMX2 SSE2Fast SSSE3 Cache64 SlowCTZ SlowAtom
  
  [libx264 @ 0x10100d400] profile Constrained Baseline, level 3.0
  
  [mpegts @ 0x10100c200] muxrate VBR, pcr every 1 pkts, sdt every 200, pat/pmt every 40 pkts
  
  Output #0, mpegts, to 'pipe:':
  
    Metadata:
  
      encoder         : Lavf52.93.0
  
      Stream #0.0: Video: libx264, yuv420p, 960x640 [PAR 1:1 DAR 3:2], q=10-51, 200 kb/s, 90k tbn, 10 tbc
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
  read pmap fffps=  3 q=37.0 size=      37kB time=0.10 bitrate=3008.0kbits/s    bits/s    
  
  video pid set at 100
  
  found sequence start
  
    next segment value 1026000
  
  written bytes 376 skipped 0
  
  frame=   54 fps=  2 q=-1.0 Lsize=     160kB time=5.40 bitrate= 242.0kbits/s    
  
  video:141kB audio:0kB global headers:0kB muxing overhead 12.872737%
  
  frame I:6     Avg QP:34.68  size: 23524
  
  [libx264 @ 0x10100d400] frame P:48    Avg QP:41.53  size:    75
  
  [libx264 @ 0x10100d400] mb I  I16..4: 63.9%  0.0% 36.1%
  
  [libx264 @ 0x10100d400] mb P  I16..4:  0.1%  0.0%  0.0%  P16..4:  0.8%  0.1%  0.0%  0.0%  0.0%    skip:99.0%
  
  [libx264 @ 0x10100d400] final ratefactor: 38.54
  
  [libx264 @ 0x10100d400] coded y,uvDC,uvAC intra: 57.7% 22.3% 2.0% inter: 0.0% 0.1% 0.0%
  
  [libx264 @ 0x10100d400] i16 v,h,dc,p: 23% 35% 27% 15%
  
  [libx264 @ 0x10100d400] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 23% 32% 16%  4%  3%  3%  7%  4%  8%
  
  [libx264 @ 0x10100d400] i8c dc,h,v,p: 83% 11%  5%  0%
  
  [libx264 @ 0x10100d400] kb/s:214.43

• FFmpeg drawtext over multiple lines

  22 novembre 2015, par Jared Glass

  I have the code :

  import subprocess , os
  
  
  
  ffmpeg = "C:\\ffmpeg_10_6_11.exe"
  
  inVid = "C:\\test_in.avi"
  
  outVid = "C:\\test_out.avi"
  
  
  
  if os.path.exists( outVid ):
  
  os.remove( outVid )
  
  proc = subprocess.Popen(ffmpeg + " -i " + inVid + ''' -vf drawtext=fontfile=/Windows/Fonts/arial.ttf:text="onLine1 onLine2 onLine3":fontcolor=white:fontsize=20 -y ''' + outVid , shell=True, stderr=subprocess.PIPE)
  
  proc.wait()
  
  print proc.stderr.read()
  
  os.startfile( outVid )

  to write text to a video file. But I want to write out many lines of text instead of just having it all on the one line.

  Pls help. Thanks