Re: [SoX-users] Confused about SOX and ALSA

[<pf...@fa...>]

Hi,

The microphone is a dodotronic ultramic: 
http://www.dodotronic.com/index.php/ultramics/. I'm working on bat
echolocation.

The reason I posted my question to this list was because I thought sox
might be using some other driver (other than audacity) behind the
scenes.

On Fri, Dec 11, 2015, at 08:05 PM, Jan Stary wrote:
> On Dec 11 17:57:21, pf...@fa... wrote:
> > I have a high sample rate (250 khz) USB microphone.
> 
> May I ask what kind of microphone this is exactly,
> and what ultrasounds you plan to record with it?
> 
> > I've tried to record from it using matlab, audacity and the command tool
> > arecord. However, to no avail. All these tools return the same error:
> > the sample rate is wrong.
> 
> I'm afraid this has nothing to do with SoX.
> Ask on _their_ mailing lists.
> 
> But I wouldn't be surprised if a recording tool refused
> to record at 250 kHz. It is also possible that it's SoX
> doing the resampling for you - on my old MacBook
> (which surely cannot record at 250000 Hz), I get
> 
>   $ rec -r 250000 file.wav
>   fCoreAudioDriverUID AppleHDAEngineInput:1
>   rec WARN formats: can't set sample rate 250000; using 44100
>   
>   Input File     : 'default' (coreaudio)
>   Channels       : 2
>   Sample Rate    : 44100
>   Precision      : 32-bit
>   Sample Encoding: 32-bit Signed Integer PCM
> 
>   In:0.00% 00:00:01.70 [00:00:00.00] Out:413kk [    |    ]    Clip:0   ^C
>   Aborted.
> 
>   $ soxi file.wav
>   
>   Input File     : 'file.wav'
>   Channels       : 2
>   Sample Rate    : 250000
>   Precision      : 32-bit
>   Duration       : 00:00:01.65 = 412896 samples ~ 123.869 CDDA sectors
>   File Size      : 3.30M
>   Bit Rate       : 16.0M
>   Sample Encoding: 32-bit Signed Integer PCM
> 
> 
> > However, using sox, I can record without problems. Generating a
> > spectrogram from sound with a known frequency confirms that the sample
> > rate is indeed 250khz - also the files contain (give or take some
> > samples) the correct number of samples.
> 
> You don't a spectrogram for that, plain old soxi(1) will tell you.
> Also, the sample rate has nothing to do with the "known frequency"
> of the sound you are recording.
> 
> > So, my question is, why can i record using sox
> > but not any of the other tools.
> 
> Ask _them_.
> 
> > In case it helps, I have attached the sox output below.
> 
> You also need to attach the command line you used.
> 
> > ----------------
> > rec:      SoX v14.4.1
> > 
> > Input File     : 'hw:2,0' (alsa)
> > Channels       : 1
> > Sample Rate    : 250000
> 
> Hm, this looks like the device _is_ actually set to 250000.
> In the example above, the devie is actually set to 44100,
> and it's SoX resampling for me (to 250000).
> 
> 	Jan
> 
> > Precision      : 16-bit
> > Sample Encoding: 16-bit Signed Integer PCM
> > Endian Type    : little
> > Reverse Nibbles: no
> > Reverse Bits   : no
> > 
> > rec INFO sox: Overwriting `test.wav'
> > 
> > Output File    : 'test.wav'
> > Channels       : 1
> > Sample Rate    : 250000
> > Precision      : 16-bit
> > Sample Encoding: 16-bit Signed Integer PCM
> > Endian Type    : little
> > Reverse Nibbles: no
> > Reverse Bits   : no
> > Comment        : 'Processed by SoX'
> > 
> > rec INFO channels: has no effect in this configuration
> > rec INFO sox: effects chain: input       250000Hz  1 channels
> > rec INFO sox: effects chain: highpass    250000Hz  1 channels
> > rec INFO sox: effects chain: vol         250000Hz  1 channels
> > rec INFO sox: effects chain: spectrogram  250000Hz  1 channels
> > rec INFO sox: effects chain: dither      250000Hz  1 channels
> > rec INFO sox: effects chain: output      250000Hz  1 channels
> > In:0.00% 00:00:04.33 [00:00:00.00] Out:1.07M [      |      ]       
> > Clip:0    ^C
> > Aborted.
> 
> 
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