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• FFMPEG - Scale video filter not providing expected results

  11 novembre 2011, par dpassera

  Apologies if this question has been asked. I couldn't find it, but if it has, please let me know and I'll close this out.

  I'm attempting a simple scale of a video whose original dimensions are 480x360 and whose target dimensions are 400x300. The video starts as an FLV and eventually needs to end up as an MPEG. I'm using the following command line to do this :

  ffmpeg -i user.flv -vf "scale=400:300" user_scaled.mpg

  When I play the scaled video in MPEG Streamclip, the scale is correct and the video info shows that the dimensions are 400x300. However, when I play the scaled video in Quicktime, the video is scaled to 478x359. More importantly, FFMPEG, itself, treats the video as being 478x359, so any future commands (trimming, conversion, overlaying, etc) executed on it result in a video of 478x359.

  The initial workflow required an FLV to MPEG conversion, but I've tried this with several different in and out formats (FLV -> FLV, FLV -> MPEG, MPEG -> MPEG, etc) all with the same results. As long as I can end up with an MPEG, though, I can deal with however many steps and conversions it would take to get this scaling working.

  I'll paste the command-line output below, and a sample input video is also linked below, if you'd like it. Thank you very much for any help.

  http://www.monkeydriver.com/dpassera/stack_flv.zip

  Command-line output :

  ffmpeg -i user.flv -vf "scale=400:300" user_scaled.mpg
  
  
  
  ffmpeg version 0.7-rc1, Copyright (c) 2000-2011 the FFmpeg developers
  
    built on May 21 2011 22:13:19 with gcc 4.1.2 20080704 (Red Hat 4.1.2-50)
  
    configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 
  
   --mandir=/usr/share/man --incdir=/usr/include --disable-avisynth
  
   --extra-cflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
  
   -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -fPIC'
  
   --enable-avfilter --enable-libdirac --enable-libgsm --enable-libmp3lame
  
   --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libx264
  
   --enable-gpl --enable-postproc --enable-pthreads --enable-shared
  
   --enable-swscale --enable-vdpau --enable-version3 --enable-x11grab
  
   --disable-yasm --enable-filters --enable-filter=movie
  
  
  
    libavutil    50. 40. 1 / 50. 40. 1
  
    libavcodec   52.120. 0 / 52.120. 0
  
    libavformat  52.108. 0 / 52.108. 0
  
    libavdevice  52.  4. 0 / 52.  4. 0
  
    libavfilter   1. 77. 0 /  1. 77. 0
  
    libswscale    0. 13. 0 /  0. 13. 0
  
    libpostproc  51.  2. 0 / 51.  2. 0
  
  
  
  [flv @ 0x11dd3b30] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, flv, from 'user.flv':
  
  
  
    Metadata:
  
      duration        : 5
  
      videocodecid    : 2
  
      audiocodecid    : 6
  
      canSeekToEnd    : true
  
      createdby       : FMS 4.0
  
      creationdate    : Mon Oct 31 11:43:44 2011
  
  
  
    Duration: 00:00:04.62, start: 0.000000, bitrate: N/A
  
      Stream #0.0: Video: flv, yuv420p, 640x480, 1k tbr, 1k tbn, 1k tbc
  
      Stream #0.1: Audio: nellymoser, 44100 Hz, mono, s16
  
  
  
  [buffer @ 0x11ddc950] w:640 h:480 pixfmt:yuv420p
  
  
  
  [scale @ 0x11dda610] w:640 h:480 fmt:yuv420p -> w:400 h:300 fmt:yuv420p flags:0xa0000004
  
  
  
  [mpeg @ 0x11dd6bd0] VBV buffer size not set, muxing may fail
  
  
  
  Output #0, mpeg, to 'user_scaled.mpg':
  
    Metadata:
  
      duration        : 5
  
      videocodecid    : 2
  
      audiocodecid    : 6
  
      canSeekToEnd    : true
  
      createdby       : FMS 4.0
  
      creationdate    : Mon Oct 31 11:43:44 2011
  
      encoder         : Lavf52.108.0
  
  
  
      Stream #0.0: Video: mpeg1video, yuv420p, 400x300, q=2-31, 200 kb/s, 90k tbn, 60 tbc
  
  
  
      Stream #0.1: Audio: mp2, 44100 Hz, mono, s16, 64 kb/s
  
  
  
  Stream mapping:
  
  Stream #0.0 -> #0.0
  
  Stream #0.1 -> #0.1
  
  
  
  Press [q] to stop encoding
  
  frame=  230 fps=  0 q=10.2 size=     366kB time=3.82 bitrate= 785.6kbits/s dup=175 drop=0 
  
  frame=  267 fps=  0 q=10.7 Lsize=     412kB time=4.43 bitrate= 761.3kbits/s dup=203 drop=0    
  
  
  
  video:370kB audio:36kB global headers:0kB muxing overhead 1.568959%

• Start/Stop Ffmpeg video capture

  2 novembre 2011, par Dasas

  I'm currently using ffmpeg for recording video from a webcam source.

  At the moment i use java to call for ffmpeg to execute.

  The code is pretty straightforward

  ffmpeg -f dshow -i video="Dualpix HD720p for Notebooks" -s cif -r 20 -f flv TEST.FLV
  
  Runtime.getRuntime().exec("rundll32 SHELL32.DLL,ShellExec_RunDLL " + cmd);

  and it works fine.

  The only real issue occour when when i need to stop the recording process.

  I know that i can press q or even ctrl+c in the CMD but i need to stop the process without keyboard input.

  That would be pretty easy to achive by killing the process but in this case ffmpeg do not finalize the video leaving me with a corrupt, need to fix, output.

  Is there any way to trigger the finalizing process "remotely".

  Thx,
  D.

  *******EDIT**********

  Thx for the prompt answer, i think you're referring to

  Process.getOutputStream()

  As for this case i have tried with this code :

  public Process doCommand(String cmd) throws Exception {
  
  
  
      rt = Runtime.getRuntime();
  
      Process proc = rt.exec(cmd);
  
      recOS= proc.getOutputStream();
  
      regcIS= proc.getInputStream();
  
  
  
      return proc;
  
  
  
  }
  
  
  
     receOS.write(("q/n".getBytes()));
  
     recOS.flush();

  I'm still getting an error, to be more specific, java.io.ioexception The pipe is being closed ...

• Extract audio amplitude from video

  11 janvier 2012, par Andrew

  I need to process >200 videos by getting several snapshots from each one.
  Each snapshot will be taken if the volume is higher than 'x'.
  So I can make snapshots with FFMPEG but I don't know how to extract the amplitude graph.
  How can I get an array with the audio volume of each frame ?