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• Passing python's file like object to ffmpeg via subprocess

  3 juillet 2012, par tejinderss

  I have a django FileField, which i use to store wav files on the Amazon s3 server. I have set up the celery task to read that file and convert it to mp3 and store it to another FileField. Problem i am facing is that i am unable to pass the input file to ffmpeg as the file is not the physical file on the hard disk drive. To circumvent that, i used stdin to feed the input stream of the file with the django's filefield. Here is the example :

  output_file = NamedTemporaryFile(suffix='.mp3')
  
  subprocess.call(['ffmpeg', '-y', '-i', '-', output_file.name], stdin=recording_wav)

  where recording_wav file is : , which is actually stored on the amazon s3 server.
  The error for the above subprocess call is :

  AttributeError: 'cStringIO.StringO' object has no attribute 'fileno'

  How can i do this ? Thanks in advance for the help.

  Edit :

  Full traceback :

  [2012-07-03 04:09:50,336: ERROR/MainProcess] Task api.tasks.convert_audio[b7ab4192-2bff-4ea4-9421-b664c8d6ae2e] raised exception: AttributeError("'cStringIO.StringO' object has no attribute 'fileno'",)
  
  Traceback (most recent call last):
  
    File "/home/tejinder/envs/tmai/local/lib/python2.7/site-packages/celery/execute/trace.py", line 181, in trace_task
  
      R = retval = fun(*args, **kwargs)
  
    File "/home/tejinder/projects/tmai/../tmai/apps/api/tasks.py", line 56, in convert_audio
  
      subprocess.Popen(['ffmpeg', '-y', '-i', '-', output_file.name], stdin=recording_wav)
  
    File "/usr/lib/python2.7/subprocess.py", line 672, in __init__
  
      errread, errwrite) = self._get_handles(stdin, stdout, stderr)
  
    File "/usr/lib/python2.7/subprocess.py", line 1043, in _get_handles
  
      p2cread = stdin.fileno()
  
    File "/home/tejinder/envs/tmai/local/lib/python2.7/site-packages/django/core/files/utils.py", line 12, in <lambda>
  
      fileno = property(lambda self: self.file.fileno)
  
    File "/home/tejinder/envs/tmai/local/lib/python2.7/site-packages/django/core/files/utils.py", line 12, in <lambda>
  
      fileno = property(lambda self: self.file.fileno)
  
  AttributeError: &#39;cStringIO.StringO&#39; object has no attribute &#39;fileno&#39;
  
  </lambda></lambda>

• ffmpeg splitting RGB and Alpha channels using filter

  29 juin 2012, par Dow

  I'm trying to use ffmpeg to split an input file into two separate files :

  1. An MP4 with only R,G and B channels
  2. An MP4 with the "extracted" A channel (a so-called Key clip, see http://ffmpeg-users.933282.n4.nabble.com/quot-Extracting-quot-Alpha-Channel-td3700227.html)

  I've managed to do both, but now I want to combine them into one single command. Here's what I do :

  ffmpeg -r $FPS -y -i input.flv -vcodec libx264 -vpre ipod640 -acodec libfaac -s 256x256 -r $FPS -filter_complex INSERT_FILTER_HERE rgb.mp4 alpha.mp4

  where INSERT_FILTER_HERE is :

  format=rgba, split [rgb_in][alpha_in];
  
  [rgb_in] fifo, lutrgb=a=minval [rgb_out];
  
  [alpha_in] format=rgba, split [T1], fifo, lutrgb=r=maxval:g=maxval:b=maxval, [T2] overlay [out];
  
  [T1] fifo, lutrgb=r=minval:g=minval:b=minval [T2]

  In short, I split the file into two streams, for the first stream, I "remove" the alpha channel, for the second stream, I extract a grayscale representation of the alpha channel. When I put this through graph2dot, it works fine, with a nullsink as output.

  However, when I run it in ffmpeg with -filter_complex, I get :

  ffmpeg version N-41994-g782763e Copyright (c) 2000-2012 the FFmpeg developers
  
    built on Jun 28 2012 17:45:15 with gcc 4.6.3
  
    configuration: --enable-gpl --enable-nonfree --enable-pthreads --enable-filters --enable-libfaac --enable-libmp3lame --enable-libx264 --enable-libtheora --enable-libvpx --enable-postproc --enable-avfilter
  
    libavutil      51. 63.100 / 51. 63.100
  
    libavcodec     54. 29.101 / 54. 29.101
  
    libavformat    54. 11.100 / 54. 11.100
  
    libavdevice    54.  0.100 / 54.  0.100
  
    libavfilter     3.  0.100 /  3.  0.100
  
    libswscale      2.  1.100 /  2.  1.100
  
    libswresample   0. 15.100 /  0. 15.100
  
    libpostproc    52.  0.100 / 52.  0.100
  
  Input #0, flv, from 'input.flv':
  
    Metadata:
  
      audiodelay      : 0
  
      canSeekToEnd    : true
  
    Duration: 00:01:10.56, start: 0.000000, bitrate: 1964 kb/s
  
      Stream #0:0: Video: vp6a, yuva420p, 800x950, 1536 kb/s, 25 tbr, 1k tbn, 1k tbc
  
      Stream #0:1: Audio: mp3, 44100 Hz, stereo, s16, 128 kb/s
  
  [graph 0 input from stream 0:0 @ 0x2e4c6e0] w:800 h:950 pixfmt:yuva420p tb:1/30 fr:30/1 sar:0/1 sws_param:flags=2
  
  Output pad "default" for the filter "Parsed_lutrgb_3" of type "lutrgb" not connected to any destination

  Any ideas on how I make ffmpeg recognize that it has to write [rgb_out] to rgb.mp4 and [out] to alpha.mp3 ?

  Thanks in advance !

• Open .avi with OpenCV 2.4 & Ubuntu 11.04

  25 juin 2012, par CTZStef

  I try to open and read video files in .avi format using OpenCV. Here is my code :

  void MainWindow::on_actionOuvrir_fichier_triggered()
  
   140    +   {
  
   141    +    //mettre a -1 streamId
  
   142    +    streamId = -1;
  
   143    +    //ouvrir fenetre navigation fichiers pour recuperer path vers .avi
  
   144    +    QString fileName = QFileDialog::getOpenFileName(this,tr("Ouvrir fichier video"),"/home",
  
   145    +    tr("Videos (*.avi)"));
  
   146    +    std::string utf8_text = fileName.toUtf8().constData();
  
   147    +    //ouvrir .avi
  
   148    +    capture = new VideoCapture(utf8_text);
  
   149    +    //check ouverture
  
   150    +    if(!capture->isOpened())
  
   151    +    cout << "probleme ouverture fichier video" << endl;
  
   152    +    //calculer delay between each frame in ms
  
   153    +    rate = capture->get(CV_CAP_PROP_FPS);
  
   154    +    delay = 1000 / rate;
  
   155    +    //demarrer timer recordId
  
   156    +    recordId = startTimer(delay);
  
   157    +    //capture premiere frame
  
   158    +    if(!capture->read(in))
  
   159    +    cout << "probleme lecture frame fichier video" << endl;
  
   160    +   }

  I get no problem at compilation time, but I can't open a video file. While in debug mode I saw that string utf8_text had the good absolute path to my video, so obviously the problem comes from the constructor of the VideoCapture object. Then, I tried to install every codec pack I could or thought was relevant. But the problem is still there, capture->isOpened() still returns false, and in debug mode I can see that capture contains nothing.

  I am lost here, don't know what to try next. Any idea ??

  Thanks !!!

  [EDIT]
  Just in case, here is the output of ffmpeg -i myFile.avi

  faraday@faraday-Compaq-Evo-D510-e-pc:~/QtProjects/visionDev$ ffmpeg -i 1.avi
  
  FFmpeg version 0.6.6-4:0.6.6-0ubuntu0.11.04.1, Copyright (c) 2000-2010 the Libav developers
  
    built on Jun 12 2012 16:28:21 with gcc 4.5.2
  
    configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
  
    WARNING: library configuration mismatch
  
    libavutil   configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libavcodec  configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libavformat configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libavdevice configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libavfilter configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libswscale  configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libpostproc configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libavutil     50.15. 1 / 50.15. 1
  
    libavcodec    52.72. 2 / 52.72. 2
  
    libavformat   52.64. 2 / 52.64. 2
  
    libavdevice   52. 2. 0 / 52. 2. 0
  
    libavfilter    1.19. 0 /  1.19. 0
  
    libswscale     0.11. 0 /  0.11. 0
  
    libpostproc   51. 2. 0 / 51. 2. 0
  
  Input #0, avi, from '1.avi':
  
    Duration: 00:02:35.39, start: 0.000000, bitrate: 110595 kb/s
  
      Stream #0.0: Video: rawvideo, bgr24, 640x480, 15 tbr, 15 tbn, 15 tbc
  
  At least one output file must be specified

  I do not see anything wrong here, but I thought maybe someone will.

  I really need this to work soon, and right now it's a dead end...

  thanks

  [EDIT 2]

  I have just read this in the book OpenCV 2 Computer Vision Application Programming Cookbook by R. Laganiere :

  It is important to note that in order to open the specified video
  file, your computer must have the corresponding codec installed,
  otherwise cv::VideoCapture will not be able to understand the input
  file. Normally, if you are able to open your video file with a video
  player on your machine (such as the Windows Media Player), then OpenCV
  should also be able to read this file.

  Well, on my machine it is not that easy mister Laganiere... I hate this book.