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• Use of the 'hash' command

  25 mars 2019, par Rob

  I’m working on a small app based on ffmpeg, and I read a tutorial made for ubuntu where they advise to use the command hash on the produced executable.

  I’m curious about that command, did you ever use it ? For which purpose ?

  When I run it in my source folder, I get this (once compiled)

  $ hash
  
  hits    command
  
     1    /usr/bin/strip
  
     1    /usr/local/bin/ffmpeg
  
     1    /usr/bin/svn
  
     4    /usr/local/bin/brew
  
     2    /usr/bin/git
  
     1    /bin/rm
  
     1    /bin/cat
  
     1    /usr/bin/ld
  
     1    /bin/sh
  
     4    /usr/bin/man
  
     5    /usr/bin/make
  
     4    /usr/bin/otool
  
    15    /bin/ls
  
     6    /usr/bin/open
  
     2    /usr/bin/clear

  Looks like a summary of my bash_history…

  When I run it on an executable file, I do not have lots of lines displayed, and nothing seems to changes in that application ?

  $ md5 ffserver
  
  MD5 (ffserver) = 2beac612e5efd6ee4a827ae0893ee338
  
  $ hash ffserver
  
  $ md5 ffserver
  
  MD5 (ffserver) = 2beac612e5efd6ee4a827ae0893ee338

  When I look for the man, it just says it’s a builtin function. Really useful :)

  It does work (let say exist) on Linux and on MacOSX.

• What ffmpeg command to use to convert a list of unsigned integers into an audio file ?

  21 mars 2019, par John

  I have a file that contains a list of about forty thousand integers that are space delimited, with each integer between the value of 0 and 255. It is this file here :

  https://github.com/johnlai2004/sound-project/blob/master/integers.txt

  If you connect a speaker to an ESP32 breakout board, then run this list of integers through the digital to analog converter at a frequency of 24kHz, you will hear the sentence, "That’s not the post that you missed."

  What I want to know is how do you use FFMPEG to convert this list of integers into a sound file that other computer can play to hear the same phrase ? I tried this command :

  ffmpeg -f u8 -ac 1 -ar 24000 -i integers.txt -y audio.wav

  But my audio.wav just sounds like white noise. I tried a few other values for -f and for -ar, but all I hear are different frequencies of white noise and maybe some extra buzzing.

  Is it possible to use ffmpeg to translate my list of integers into an audio file for other computers to play ? If so, what’s the correct ffmpeg command to do this ?

  OTHER NOTES

  If it helps, this is the sketch file that I upload to an ESP32 if I want to hear the audio :

  https://github.com/johnlai2004/sound-project/blob/master/play-audio.ino

  In short, the file looks like this :

  #define speakerPin 25                          //The pins to output audio on. (9,10 on UNO,Nano)
  
  #define bufferTotal 1347
  
  #define buffSize 32
  
  
  
  byte buffer[bufferTotal][buffSize];
  
  int buffItemN = 0;
  
  int bufferN = 0;
  
  
  
  hw_timer_t * timer = NULL;
  
  portMUX_TYPE timerMux = portMUX_INITIALIZER_UNLOCKED;
  
  
  
  void IRAM_ATTR onTimer() {
  
    portENTER_CRITICAL_ISR(&timerMux);
  
  
  
  
  
    byte v = buffer[bufferN][buffItemN];
  
    dacWrite(speakerPin,v);
  
  
  
    buffItemN++;
  
  
  
    if(buffItemN >= buffSize){                                      //If the buffer is empty, do the following
  
      buffItemN = 0;                                              //Reset the sample count
  
      bufferN++;
  
      if(bufferN >= bufferTotal)
  
        bufferN = 0;
  
    }
  
  
  
    portEXIT_CRITICAL_ISR(&timerMux);
  
  
  
  }
  
  
  
  void setup() {      
  
  
  
  /* buffer records */
  
  buffer[0][0]=88;  // I split the long list of integers and load it into a 2D array
  
  buffer[0][1]=88;
  
  buffer[0][2]=86;
  
  buffer[0][3]=85;
  
  //etc....
  
  buffer[1346][28]=94;
  
  buffer[1346][29]=92;
  
  buffer[1346][30]=92;
  
  buffer[1346][31]=95;
  
  
  
  
  
  /* end buffer records */
  
  
  
    timer = timerBegin(0, 80, true);
  
    timerAttachInterrupt(timer, &onTimer, true);
  
    timerAlarmWrite(timer, 41, true);
  
    timerAlarmEnable(timer);
  
  
  
  }
  
  
  
  void loop() {
  
  
  
  }

  The buffer... is the list of integers found in the integers.txt file.

• Sox mute white noise silences keeping the lenght of the audio file [on hold]

  1er mars 2019, par Lya1981

  I have an audio which is 200 seconds long.
  I run the following command, which removes silences within the threshold specified :

  sox in.wav out.wav silence 1 0.1 1% -1 0.5 1%

  Once those silences are removed, the audio becomes 100 seconds long, which means I am losing my original time stamps.

  I need to basically blank out / mute those silences (they are variations of white noise), leaving equivalent gaps in their place in order to keep the original length and timestamps within the audio.

  Is there any way to do it with exactly the params above, just not trimming it but blanking it out ? They produce the perfect outcome but I really need to keep the time stamps...
  Thank you in advance !