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• JavaCV on Android : UnsatisfiedLinkError from libjniavdevice.so / dlopen failed cannot locate symbol "av_input_audio_device_next"

  8 septembre 2014, par liorg

  I am trying to work with JavaCV’s FFmpegFrameGrabber on Android 4.4.2 / 4.3.1 .

  Inside the onCreate(...) method I am calling :

  FFmpegFrameGrabber grabber = new FFmpegFrameGrabber(path)

  This causes the following runtime error :

  dlopen("/data/app-lib/com.example.testjavacv-1/libjniavdevice.so")
  
  failed: dlopen failed: cannot locate symbol "av_input_audio_device_next"
  
  referenced by "libjniavdevice.so"

  Other (possible) relevant information :

  1) I have included all the JavaCV .so libraries inside the libs/armeabi and libs/x86 folders.

  2) I have given the application permissions to read/write to external storage and access the camera and microphone.

  3) I am NOT statically loading any of the JavaCV native libraries before instantiating FFmpegFrameGrabber. This is because,

  • Some of the libraries cause runtime exceptions when I attempt to load them statically by myself.
  • I get the impression that JavaCV handles it’s own native library loading - for example the error I get ocurrs even though I have not requested to load the jniavdevice.so library and happens only if the ... new FFmpegFrameGrabber(...) ... code is present.

  4) I have taken a look at : https://groups.google.com/forum/# !topic/javacv/bgB5rCv_fVM which seems to address a similar issue, but the suggested solutions don’t seem to work.

  Any help on this issue would be much appreciated,
  Cheers !

• Serve a single frame of a video to a user as an image (efficiently)

  23 juillet 2014, par JoeRocc

  Problem :

  I have multiple 60 minute videos on my server (shared hosting). I need to serve a single frame of any one of these videos to a user instantly and efficiently. Expected maximum load is about 100 requests per minute.

  Notes :

  • I am on a shared hosting service, so FFmpeg is not a possibility (is FFmpeg efficient enough for 100 requests per minute anyway ?).
  • I don’t want to store hundreds of thousands of images on my server (my inodes are limited).

  Possible Solutions :

  • Load the video onto the client-side and then extract a frame and paint it to a canvas as per this article. Though I don’t want the user to have to download the whole video just to get a frame (will they have to do this ?).
  • Use some efficient server-side library to efficiently extract a frame and then serve it to the user.
  •  ???

• shell script : ffmpeg can't either read arguments or filenames, if spaces in path- or filename

  9 juillet 2014, par Nicolas

  I’m currently working on a bash shell script on OS X to get a custom tailored Pashua GUI/automatization package, using ffmpeg in the back, to transcode videos, label them, zip them, upload them, organize them and so on. Everything is working like a charm so far.

  My problem now is that I can’t make ffmpeg take files or paths that have spaces in them IF I use variables in variables. But that (I think) is a must in order to get ffmpeg to transcode multiple files at once depending on the formats and checkboxes the user ticks on.

  I made a little example snippet so you can see my dilemma.

  No spaces in path or filename / works great :

  #!/bin/bash
  
  
  
  infile='/Users/nicolas/Desktop/MASTER_[DE]_Test_140626.mov'
  
  
  
  gen_outfile () {
  
      outfile="${1/MASTER/TRANSCODE}"
  
      ffmpeg_cl="-s $2 -c:v libx264 -preset slow -crf 18 -pix_fmt yuv420p -c:a aac -b:a 240k -strict -2 $outfile"
  
  }
  
  
  
  gen_outfile "$infile" 1920x1080
  
  
  
  ./ffmpeg_stat -i "$infile" $ffmpeg_cl

  The output is as expected and the file is called "TRANSCODE_[DE]_Test_140626.mov"

  Filename variable with spaces - directly fed to ffmpeg :

  This works as well but isn’t really usable for me because I need to have the option of variable numbers of output files and arguments generated dynamically.

  #!/bin/bash
  
  
  
  infile_full='/Users/nicolas/Google Drive/encode-o-mat/MASTER_[DE] Test  140626.mov'
  
  
  
  gen_outfile () {
  
      outfile="${1/MASTER/TRANSCODE}"
  
      ffmpeg_cl="-s $2 -c:v libx264 -preset slow -crf 18 -pix_fmt yuv420p -c:a aac -b:a 240k -strict -2"
  
  }
  
  
  
  gen_outfile "$infile_full" 1920x1080
  
  
  
  ./ffmpeg_stat -i "$infile_full" $ffmpeg_cl "$outfile"

  The output is as expected and the file is called "TRANSCODE_[DE] Test 140626.mov".
  But this way is just not an option.

  This here does not work ! Filename is split up and incomplete :

  #!/bin/bash
  
  
  
  infile_full='/Users/nicolas/Google Drive/encode-o-mat/MASTER_[DE] Test  140626.mov'
  
  
  
  gen_outfile () {
  
      outfile="${1/MASTER/TRANSCODE}"
  
      ffmpeg_cl="-s $2 -c:v libx264 -preset slow -crf 18 -pix_fmt yuv420p -c:a aac -b:a 240k -strict -2 $outfile"
  
  }
  
  
  
  gen_outfile "$infile_full" 1920x1080
  
  
  
  ./ffmpeg_stat -i "$infile_full" $ffmpeg_cl

  Ffmpeg gives this error : "Unable to find a suitable output format for ’/Users/nicolas/Google’".
  Of course.

  This doesn’t work as well ! Quoting and such :

  ./ffmpeg_stat -i "$infile_full" "$ffmpeg_cl"

  If I put the $ffmpeg_cl variable in various quotes ffmpeg doesn’t understand the arguments anymore ! This is one example output :

  "Unrecognized option ’s 1920x1080 -c:v libx264 -preset slow -crf 18 -pix_fmt yuv420p -c:a aac -b:a 240k -strict -2 /Users/nicolas/Google Drive/encode-o-mat/TRANSCODE_[DE] Test 140626.mov’.
  Error splitting the argument list : Option not found
  Conversion failed !"

  It’s really important that the script can handle path- and filenames with spaces because I can’t change the environment in which that tool is supposed to run. All ideas and solutions are more than welcome !