Google Coral Dev Board not picking up Sound / Input

Question

I am working with the google coral dev board, I have managed to set up the board and run the demo where it detects cars or vans. Next, I want to move on to voice commands. On the Coral website, they have a project “Keyword Spotting”. Which seemed like exactly what I was after. I put the project onto my board and went to try it out. However no luck. The board does not detect any sound. I tried using a 3.5mm headphone with a microphone (which works on other devices, no drivers). Looking into the Dev Board specs it has two built-in PDM microphones. No idea why it detects no input whatsoever

I followed the tutorial on the google APC youtube channel I have tried, checking drivers for the board. Tried opening up the sound settings using alsamixer Tried recording a small sample with and without the headphones arecord -d test.wav. This is creating the .wav files but no audio is captured. Tried detecting audio devices on the board.

But still, at this time no success and I am finding it difficult to find other online resources for this problem. Is there something I have overlooked?

Any help will be much appreciated. Thanks.

Answer 1

I ran into same issue. Turned out just need to set arecord flags.

For instance, plugging a headphone set into the 3.5mm audio jack, then running

arecord -D hw:0,0 -c 2 test.wav -f S16_LE -d 3

worked for me.

Debugging with terminal (optional)

Some notes from my debugging process.

mediainfo displays information about files in a nice human-readable format.

To visualize (so don't have to trust replaying through the same audio port) the wav file, I did this. I used sox convert to a spectrogram (image), then converted to a jpg because for some reason jp2a only takes jpg (despite the jp2a docs implying png is accepted).

sox loud.wav -n spectrogram; convert spectroram.png spectrogram.jpg; jp2a spectrogram.jpg

You can try something like silence and compare with saying a lot of ps or tapping the microphone to ensure it is recording.

Here is the results (although I'm running on laptop not the coral dev board) of a visualization of "p"ahs .

sox test.wav -n spectrogram; convert spectrogram.png spectrogram.jpg; jp2a spectrogram.jpg
                                                                                                                                  
                                                                                                                                  
       ................................'.......................''..................................................... .          
        ..........................'',;,,;,'...............',;;;;,'......................'',;::,'............''''''''..            
     .............................',::;:;,................';cc::;'......................',;clc;'...........'''''''''...           
        ..........................',cc:;;''...............':ll:;;'......................';ccl:;'...........''''''''''..           
        ..........................,col:;;,'...............',::cl:'......................';cc::;''..........''''''''''..    :k.    
     ..............''.............,cllclc;'...............':llcc:'......................,:c:;;,'...........''''''''''..    dW.    
        .............''...........;odolc:,'...............';lllc;'.....................',cllll:,..........'''''''''''..    dW'    
     . ............'.''...........,lddoc:,'...............;odlc:;''.....................,lol::;,..........''''''''''''.    dN.    
        ..........''..............,coooll;'...............,coolc:,'.....................,clodxo;'.........''''''''''''.    oN'    
       ...........''..............,:lodxdc'...............,ldoddl;'.....................;oxddxdc'.........''''''''''''.    lK.    
       ...........'''.............:dkxddo:'..............';oxxool;'....................'cxkkxdc,'......'''''''''''''''.    cO.    
        ..........'''.............;dkkkkko,''.............;lddxxd:'....................';odollc,'......'''''''''''''''.    :k.    
     .............'''.............,codoooc'...............;dxdoc;''....................'ckkkxd:''......'''''''''''''''.    ;d.    
        ..........''....'.........,lddolc;'..............';ldxxoc,.....................':dxxoc:''.......''''''''',''''.    ,c.    
      ............'''...'.........;oxxxoc:'..............';oxdddo;'.....................,lxkkxc,'......''''','''',,'''.    .;     
 ..     ..........'''...''........,oxxxdl:'...............:dxxxxo;'.....................;dxxooc,'......'''',,,''',,,''.    .' .   
 ..    ...........'''...''........;dxddxdl,..............':dxxdoc,'....................';oxkOxo,'.....''''',;;,'',;,''.    .'     
  .    ..........''''..'''........;oxxxxdc,'.............';dkxkkx:'....................'cxxxddoc'.....''''',;;'',;;,''.    .'     
  '     .........''''..'''.......'ck00kkxd;'.............';dxxdol;'....................'ckkxxxo:'.....''''',;;,',;:;''.    .'     
  '   ...........''''...''.......'ckOOxdoc,'''...........';xOOkkxl,''..................'lOOkddoc''''..'''',:c:,,;::;''.    .'     
 ..     .........''''............'cxOkkxxo,''............'cxOOkxl;'....................'cxkkxxo:''....'''',;::,,;::;,'.    ..     
      ...........''''............';okOkdol;'''...........'lkOOkxdc''''.................';ldkkkxl''''..'''';c:;,,;:;,''.    ..     
        .........''''.............;dO0OOxo,''''.'........';lxkkdo:'''..................';dO0OOOd;''.'''''',;:;,;::;,''.    .. .   
       ..........''''.............:xO00kdl,'''...........'lkO000Oo;'''''''''...........'ckOO0K0x;,'''''''';:::;;:::;,'.    ..     
       ..........''''............'ckO0KKKOl;,''''''..'...'lxO0Odl:'''............'.....':dO0OOko,''''''''';cll::looc,'.     . .   
        ..........'''.....'......'cxO00Okd:''..'.........'oO00KK0x;'''''''.............'ck00O0Od,''''''''';colccllll:,.     .     
        ..........''.............'lO0KKKOd:,''''''.......'oO0OOxdl,'''..'..............'cxOO00Od;'''''''',lddddddooolc.           
        ..................'......'cxO0Okkd:''............'lxk0K0Oo;,''''..''.....'.....':k00KXKk:,''''''',ldxxdxkkxdl:.           
     .........''..''''....'......'cxOO0K0xc:;,''''''''''',dO00Oxoc''''....'....'..'....'oOKKKKKO:,'''''',cdxkkxkOxkkoc.           
       ...........'''....'''.....'lk000KK0d,,''''........,x0KKKXX0l;;,''''''''..'''....'oO0O0XK0l,,'''',,:oxkxxO0Okxoo.        .  
       ...''...'...''''''''''.''''oOKKK0OOo,''''''..'''..,kKK0OO0k:'''''''''''..''''...'lkOOkxdo;'''''',;okOOkkOOOOkdo.           
      ....''''''''''''''.''''''.',x0KK00K0d,'''''''''''.',xKXX00Ox;'''''''''''''''....',kKKKOOkl,'''''',:x0KKK000K00Ox.        .  
        .'''''''''''''''''''''''''dOKK0Oxo:'''''''''''''',dOKKKOdc,'''''''''''''''''''',dO0Oxxxl,''''''':k0KKK00KKK0Ox.     .'.   
       ...''''''''''''''''''''''',kKXXX0Okl,''''''''''''':k0KXXKOx;'''''''''''''''''''',xKNX0OOd;''''''':O0KXKKXKKKK0O'           
        .'''''''''''''''''''''''''lOKKKOkxc'''''''''''''',ok0KK0kd:'''''''''''''''''''''lxO0kkOx:'''''''ck0KXK0KKKK0Ok.           
      . . .... ... ............. .....,,.','..'.'..........',,'',;,.'''..''....'..'....''.,,,''',..''...''..,,'.',,..'..          
                                                                                                                                  
                                                            ... ..

vs. one of silence

$ sox test.wav -n spectrogram; convert spectrogram.png spectrogram.jpg; jp2a spectrogram.jpg
                                                                                                                                  
                                                                                                                                  
       ................................................................................................................           
        ..............................................................................................................            
     ..................................................................................................................           
       ................................................................................................................           
        ..............................................................................................................     :k.    
     ..................................................................................................................    dW.    
        ..............................................................................................................     dW'    
     . ................................................................................................................    dN.    
        ..............................................................................................................     oN'    
       ................................................................................................................    lK.    
       ................................................................................................................    cO.    
        ..............................................................................................................     :k.    
     ..................................................................................................................    ;d.    
        ...............................................................................................................    ,c.    
      .................................................................................................................    .;     
 ..     ...............................................................................................................    .' .   
 ..    ................................................................................................................    .'     
  .    ................................................................................................................    .'     
  '     ..............................................................................................................     .'     
  '   .................................................................................................................    .'     
 ..     ..............................................................................................................     ..     
      ................................................................................................................     ..     
        ...............................................................................................................    .. .   
       ................................................................................................................    ..     
       ..............'''..............................................'................................................     . .   
        ...............................................................................................................     .     
        ..........................................''...................................................................           
        ..........''......'''......'...................''''.................'................'''.....''................           
     .....'''.''.....'''....''...............................'''..''.......'...'..'.......'.....'''''''''''''..''''....           
       ....''....'''..''''...............''...........'...''''''....''...................'''.....'''''.....'''.........        .  
       ...'''..''.'''...''.......''......''...''.....'...'..''.........'''''''''''''''........''''''...'...............           
      .....'.......''''...''...'''''....'.'''''''''''''''''''''''...'''''''''''''.''''''.''''''.''''''''''''..''''.....        .  
        .'''''''.''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''..'''''''''''''''''.'''''''''''''...     .'.   
       .''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''...           
        ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''.           
      . ................... ................ .........  ..................... ...   ...................  .........   . .          
                                                                                                                                  
                                                            ... ..                                                                
...... '...

If there is literally no input (e.g. if you just use arecord test.wav) you will see emptiness:

mendel@vexing-apple:~/whisper.cpp$ sox test.wav -n spectrogram ; convert spectrogram.png spectrogram.jpg ; jp2a spectrogram.jpg
                                                                                                                                 
                                                                                                                                 
       .                                                                                                                         
                                                                                                                                 
       .                                                                                                                         
                                                                                                                                 
                                                                                                                          lK,    
     ...                                                                                                                  dW,    
                                                                                                                          dW;    
                                                                                                                          dN,    
                                                                                                                          oX,    
                                                                                                                          lK'    
       .                                                                                                                  cO'    
                                                                                                                          :x.    
      .                                                                                                                   ,o.    
                                                                                                                          ':.    
                                                                                                                          .,     
 ..                                                                                                                       .'.    
  .                                                                                                                       .'     
  .    .                                                                                                                  .'..   
  '                                                                                                                       .'     
  .                                                                                                                       .'     
      .                                                                                                                   ..     
                                                                                                                          .. .   
      ..                                                                                                                  ..     
                                                                                                                           .     
                                                                                                                           .     
                                                                                                                                 
                                                                                                                                 
      ..                                                                                                                         
                                                                                                                              .  
                                                                                                                                 
                                                                                                                              .  
                                                                                                                           ...   
                                                                                                                                 
                                                                                                                                 
      .                            .                                           .          .                           .