Advice for audio recording

Michael Reifenberger mike at
Sat Oct 21 10:55:45 UTC 2017

Zitat von Hans Petter Selasky <hps at>:

> On 10/20/17 17:37, Michael Reifenberger wrote:
>> (Hmm, why dev.pcm.4.rec.vchanformat: s16le:2.0 , shouldn't it be s24le:2.0?)
> Hi,
> You should override this into s24le:2.0 - yes. Further you should  
> set bitperfect to avoid resampling issues and the software volume  
> control. The DSP device will then refuse to open in any other ways  
> than what is printed in dmesg, with regards to sampling rate and  
> sample size and channels.
> In 11- and 12- you can simply put dev.pcm.4.rec.vchanformat=xxx in  
> the kernel environment (man kenv) or in /boot/loader.conf (requires  
> reboot) and these settings will be programmed automatically for pcm  
> #4 every time you plug this device.

Thanks for the hints!

I can now:
% dd if=/dev/dsp4.0 of=/tmp/s24le2.raw count=10000
and read as 24bit LE stereo 96khz RAW into audacity or directly with sox:
% sox -r96k -esigned -b24 -c2 -t raw /dev/dsp4.0 s24le2.flac

flac123 doesn't like 24bit flac file, only 16bit flac files get played...

> At home I'm using:
> Which I'm very happy with. It works well with FreeBSD and is  
> controlled via a wireless pad (iOS or Android at your choice).
Thats for sure a quite big/professional "home" recording machine :-)

Thanks a lot for your help!


Michael Reifenberger

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