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• How do I properly enable ffmpeg for matplotlib.animation ?

  7 mars 2017, par spanishgum

  I have covered a lot of ground on stack so far trying to get ffmpeg going so I can make a timelapse video.

  I am on a CentOS 7 machine, running python3.7.0a0.

  python3
  
  >>> import numpy as np
  
  >>> np.__version__
  
  '1.12.0'
  
  >>> import matplotlib as mpl
  
  >>> mpl.__version__
  
  '2.0.0'
  
  >>> import mpl_toolkits.basemap as base
  
  >>> base.__version__
  
  '1.0.7'

  I found this github gist on installing ffmpeg. I used the chromium source, and installed without a prefix option (using the default).

  I have confirmed that ffmpeg is installed, although I don’t know anything about testing whether it works.

  which ffmpeg
  
  /usr/local/bin/ffmpeg
  
  
  
  ffmpeg -version
  
  ffmpeg version N-83533-gada281d Copyright (c) 2000-2017 the FFmpeg dev elopers
  
  built with gcc 4.8.5 (GCC) 20150623 (Red Hat 4.8.5-11
  
  configuration:
  
  libavutil      55. 47.100 / 55. 47.100
  
  libavcodec     57. 80.100 / 57. 80.100
  
  libavformat    57. 66.102 / 57. 66.102
  
  libavdevice    57.  2.100 / 57.  2.100
  
  libavfilter     6. 73.100 /  6. 73.100
  
  libswscale      4.  3.101 /  4.  3.101
  
  libswresample   2.  4.100 /  2.  4.100

  I tried to run a few sample examples I found online :

  [1] http://matplotlib.org/examples/animation/basic_example_writer.html

  [2] http://stackoverflow.com/a/23098090/3454650

  Everything works fine up until I try to save the animation file.

  [1]

   anim.save('basic_animation.mp4', writer = FFwriter, fps=30, extra_args=['-vcodec', 'libx264'])

  [2]

  im_ani.save('im.mp4', writer=writer)

  I found here that explictly setting the path to ffmpeg might be necessary so I added this to the top of the test scripts :

  plt.rcParams['animation.ffmpeg_path'] = '/usr/local/bin/ffmpeg'

  I tried a few more tweaks in the code but always get the same response, which I do not know how to begin deciphering :

  Traceback (most recent call last):
  
    File "testanim.py", line 27, in <module>
  
      writer.grab_frame()
  
    File "/usr/local/lib/python3.7/contextlib.py", line 100, in __exit__
  
      self.gen.throw(type, value, traceback)
  
    File "/usr/local/lib/python3.7/site-packages/matplotlib/animation.py", line 256, in saving
  
      self.finish()
  
    File "/usr/local/lib/python3.7/site-packages/matplotlib/animation.py", line 276, in finish
  
      self.cleanup()
  
    File "/usr/local/lib/python3.7/site-packages/matplotlib/animation.py", line 311, in cleanup
  
      out, err = self._proc.communicate()
  
    File "/usr/local/lib/python3.7/subprocess.py", line 836, in communicate
  
      stdout, stderr = self._communicate(input, endtime, timeout)
  
    File "/usr/local/lib/python3.7/subprocess.py", line 1474, in _communicate
  
      selector.register(self.stdout, selectors.EVENT_READ)
  
    File "/usr/local/lib/python3.7/selectors.py", line 351, in register
  
      key = super().register(fileobj, events, data)
  
    File "/usr/local/lib/python3.7/selectors.py", line 237, in register
  
      key = SelectorKey(fileobj, self._fileobj_lookup(fileobj), events, data)
  
    File "/usr/local/lib/python3.7/selectors.py", line 224, in _fileobj_lookup
  
      return _fileobj_to_fd(fileobj)
  
    File "/usr/local/lib/python3.7/selectors.py", line 39, in _fileobj_to_fd
  
      "{!r}".format(fileobj)) from None
  
  ValueError: Invalid file object: &lt;_io.BufferedReader name=6>
  
  </module>

  Is there something with my configuration that is malformed ? I searched google for this error for some time but never found anything relevant to animations / ffmpeg. Any help would be greatly appreciated.

  ---

  UPDATE :

  @LordNeckBeard pointed me here : https://trac.ffmpeg.org/wiki/CompilationGuide/Centos

  I ran into problems with installing the x264 encoding dependency. Some files in libavcodec/*.c (in the make output) were reporting undefined references to several functions. After a wild goose chase found this : https://mailman.videolan.org/pipermail/x264-devel/2015-February/010971.html

  To fix the x264 installation, I simply added some configure flags :

  ./configure --enable-static --enable-shared --extra-ldflags="-lswresample -llzma"

  ---

  UPDATE :

  So everything installed fine after fixing the libx264 problems. I went ahead and copied the ffmpeg binary from the ffmpeg_build folder into /usr/local/bin/ffmpeg.

  After running the script I was getting problems where ffmpeg could not find the libx264 shared object. I think I will have to recompile everything using different prefixes. My intuition tells me there are old files laying around after I have messed with everything, using some configuration that is broken.

  So I decided maybe I should just try to use NUX : http://linoxide.com/linux-how-to/install-ffmpeg-centos-7/
  I installed ffmpeg using the new rpm, but to no avail. I still was not able to run ffmpeg because of a missing shared object.

  Finally, instead of usiong files copied into my /usr/local/bin folder, I ran ffmpeg directly from the build bin directory. Turns out that this does work properly !

  So in essence, if I want to install ffmpeg system wide, I need to manually compile from sources again but using a nonlocal prefix.

• Fluent-ffmpeg Node.js overlay audio

  10 avril 2017, par Dineshkarthik Raveendran

  Using fluent-ffmpeg am trying to merge a set of videos into a single video, which am able to achieve with the following code :

     var ffmpeg = require('fluent-ffmpeg'),
  
          command = ffmpeg(), 
  
          videoNames = ['video1.mp4', 'video2.mp4', 'video3.mp4'];
  
  
  
      videoNames.forEach(function(videoName){
  
          command = command.addInput(videoName);
  
      });
  
      command.mergeToFile('output.mp4')
  
      .on('error', function(err) {
  
          console.log('Error ' + err.message);
  
      })
  
      .on('end', function() {
  
          console.log('Finished!');
  
      });

  In additon to the above am trying to overlay an audio to the merged video without removing the existing audio. What am trying to do is replicate the following command line using fluent-ffmpeg wrapper

  ffmpeg -i io1.mp4 -i io2.mp4 -i io3.mp4 -i io4.mp4 -i io5.mp4 -i io6.mp4 -i audio.mp3 -filter_complex '[0:a][1:a][2:a][3:a][4:a][5:a]concat=n=7:v=0:a=1,volume=1[aout];[6]volume=0.1[bout];[aout][bout]amerge=[tout];[0:v][1:v][2:v][3:v][4:v][5:v]concat=n=6:v=1:a=0[v1]' -map [v1] -map [tout] -c:a aac -b:a 96K  -shortest -y out.mp4

  Tried the following but unable to implement the filter_complex with streams properly

  var ffmpeg = require('fluent-ffmpeg'),
  
      command = ffmpeg(), 
  
      videoNames = ['video1.mp4', 'video2.mp4', 'video3.mp4'];
  
  
  
  videoNames.forEach(function(videoName){
  
      command = command.addInput(videoName);
  
  });
  
  command.addInput("myAudio.mp3")
  
          .audioFilters('volume=0.1'); // trying to overlay new audio without removing existing audio
  
  command.mergeToFile('output.mp4')
  
  .on('error', function(err) {
  
      console.log('Error ' + err.message);
  
  })
  
  .on('end', function() {
  
      console.log('Finished!');
  
  });

  Which throw the error Error ffmpeg exited with code 1: Cannot find a matching stream for unlabeled input pad 6 on filter Parsed_concat_0

• avio_open crashes, avcodec_copy_context doesn't work

  5 mars 2017, par Nulano

  I’m trying to port https://ffmpeg.org/doxygen/trunk/doc_2examples_2remuxing_8c-example.html to JavaCPP Presets for FFmpeg https://github.com/bytedeco/javacpp-presets/tree/master/ffmpeg.

  I have this so far :

  av_register_all();
  
  
  
  AVFormatContext inFmtCtx = new AVFormatContext(null);
  
  if (avformat_open_input(inFmtCtx, "file.ts", null, null) != 0)
  
      throw new Exception("Could not open input file");
  
  if (avformat_find_stream_info(inFmtCtx, (PointerPointer)null) != 0)
  
      throw new Exception("Failed to retrieve input stream information");
  
  av_dump_format(inFmtCtx, 0, "file.ts", 0);
  
  
  
  AVFormatContext outFmtCtx = new AVFormatContext(null);
  
  avformat_alloc_output_context2(outFmtCtx, null, null, "file2.ts");
  
  AVOutputFormat outFmt = outFmtCtx.oformat();
  
  for (int i = 0; i < inFmtCtx.nb_streams(); i++) {
  
      AVStream inStr = inFmtCtx.streams(i);
  
      AVStream outStr = avformat_new_stream(outFmtCtx, inStr.codec().codec());
  
      if (outStr.isNull()) throw new Exception("Failed allocating output stream");
  
      if (avcodec_copy_context(outStr.codec(), inStr.codec()) != 0)
  
          throw new Exception("Failed to copy context from input to"+
  
                              " output stream codec context");
  
      if ((outFmtCtx.oformat().flags() & AVFMT_GLOBALHEADER) != 0)
  
          outStr.codec().flags(outStr.codec().flags() | CODEC_FLAG_GLOBAL_HEADER);
  
  }
  
  av_dump_format(outFmtCtx, 0, "file2.ts", 1);
  
  
  
  if ((outFmt.flags() & AVFMT_NOFILE) == 0)
  
      if (avio_open(outFmtCtx.pb(), "file2.ts", AVIO_FLAG_WRITE) != 0)
  
          throw new Exception("Could not open output file");

  The problem is, that the avio_open call causes the JVM to crash with an access violation.

  Stack: [0x00000000037e0000,0x00000000038e0000],  sp=0x00000000038df6d0,  free space=1021k
  
  Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
  
  C  [avformat-57.dll+0x28877]
  
  C  [jniavformat.dll+0x383cb]
  
  C  0x0000000003bcdfcc
  
  
  
  Java frames: (J=compiled Java code, j=interpreted, Vv=VM code)
  
  j  org.bytedeco.javacpp.avformat.avio_open(Lorg/bytedeco/javacpp/avformat$AVIOContext;Ljava/lang/String;I)I+0
  
  j  TestRemuxer.main([Ljava/lang/String;)V+226
  
  v  ~StubRoutines::call_stub

  This is the output (without the crash message) :

  Input #0, mpegts, from 'file.ts':
  
    Duration: 00:00:17.60, start: 0.000000, bitrate: 1016 kb/s
  
    Program 1 
  
      Stream #0:0[0x100]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p(progressive), 636x480 [SAR 900:901 DAR 45:34], 23.98 fps, 23.98 tbr, 90k tbn, 47.95 tbc
  
      Stream #0:1[0x101]: Audio: aac (LC) ([15][0][0][0] / 0x000F), 44100 Hz, stereo, fltp, 194 kb/s
  
  Output #0, mpegts, to 'file2.ts':
  
      Stream #0:0: Unknown: none
  
      Stream #0:1: Unknown: none

  I suspect the cause of the access violation is the same as what causes the output streams to be unknown. However, if I pause debugging on the second av_dump_format call, I can use Evaluate to verify, that the codecs were copied properly. (I checked the FFmpeg sources, and I know that a stream is dumped as Unknown, if and only if its codec_type is set to an invalid value, however the value is correctly 0 for the first stream and 1 for the second stream.)