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• Making Sound To High To Hear Or Undetecable with Sox/FFMPEG

  28 octobre 2016, par Devin Dixon

  I want to make a sound that is too high to be detected by the human ear. From my understanding, humans can hear sounds between 20hz and 44000hz.

  With sox, I am making a sound that is 50000hz. The problem is I can still hear it. The command I am using is this :

  sox -n -r 50000 output.wav rate -L -s 50050 synth 3 sine 

  Either I have super good hearing or I am doing something wrong. How can I make this sound undetectable with SOX of FFMPEG ?

• How to use FFMPEG commands

  26 septembre 2013, par Shashank Agarwal

  In android i am making an app in which it will record an video and crop the video from center for doing so i found FFMPEG over google. I followed http://dmitrydzz-hobby.blogspot.in/2012/04/how-to-build-ffmpeg-and-use-it-in.html

  It works fine but i want to know how to use this `ffmpeg -y -i /sdcard/videokit/short.mp4 -vf crop=100:100:0:0 -s 320x240 -r 15 -aspect 3:4 -ab 12288 -vcodec mpeg4 -b 2097152 -sample_fmt s16 /sdcard/videokit/out.mp4

  ` video cropping command and Where to write this command.

  I have tried this (for concatenation just to check about how to use ffmpeg command )

  public class MainActivity extends Activity {
  
  private static native int logFileInfo(String[] args);
  
  String pathOut = "/storage/sdcard/12.mp3";
  
  String pathInM = "/storage/sdcard/23.mp3";
  
  String pathIn = "/storage/sdcard/out.mp3";
  
  @Override
  
  public void onCreate(Bundle savedInstanceState) {
  
      super.onCreate(savedInstanceState);
  
      setContentView(R.layout.activity_main);
  
      String[] args = {"ffmpeg",  "-i", "concat:", pathOut, "|",pathInM ,pathIn};
  
      logFileInfo(args);
  
      //logFileInfo("/storage/sdcard/12.mp3");
  
  }
  
  
  
  static
  
  {
  
      System.loadLibrary("mylib");
  
  }

  But i dont know what to write in mylib.c to execute this.somebody Please help

• Renaming Carrierwave extension before saving it [on hold]

  2 septembre 2013, par Jan

  I am trying to get a mp3 version of a wav which gets watermarked by using ffmpeg.

  Spoken in steps :

  • upload wav (works)
  • watermark it (works also)
  • make a mp3 version (does not work)

  The upload and watermarking step is done correctly.

  My problem is, that ffmpeg evaluates the destination format by reading its file extension name (which is wav in my case). How can I rename the extension before it get's saved ?

  ffmpeg -i watermarked.wav -acodec libmp3lame -f mp3 watermarked.wav
  
                       HOW CAN I RENAME THIS BEFORE IT GET SAVED? ^^^

  The above snip (-f forcing the codec and format) does NOT it's job and

  def full_filename(for_file=file)
  
    super.chomp(File.extname(super)) + '.mp3'
  
  end 

  is happening too late (after processing)

  Do I have to make a seperate (second) tempfile and remove the watermarked.wav ?
  Or do I have to make a "seperate process" and take ?
  And when yes, how ?

  I am trying this since weeks...

  many, many, many thanks in advance