Issue with external audio devices on MacOS

[Schumacher Marlon <marlon.schumacher@music.mcgill.ca>]

Dear sox-developers,

Thank you first of all for developing and maintaining such a useful and versatile tool! 

I've been trying to find a way to use sox (14.4.1) on MacOS (10.7.5) with external audio devices, such as the "RME Fireface 800" or the "MOTU 828MK2" for playback of multichannel audio. In order to do this I tried two strategies:

1) Choose the audio device (Fireface 800) as the system's default audio device and use the option -d (to playback a stereo soundfile using this command:

$sox  /Users/Marlon_MBPro3/drumLoop.aif  -d

(
/Users/Marlon_MBPro3/drumLoop.aif:

 File Size: 614k      Bit Rate: 1.41M
  Encoding: Signed PCM    
  Channels: 2 @ 16-bit   
Samplerate: 44100Hz      
Replaygain: off         
  Duration: 00:00:03.48  

In:100%  00:00:03.48 [00:00:00.00] Out:153k  [     -|      ] Hd:1.0 Clip:0    
Done.
)

Which resulted in distorted  (crackles/clipping) and transposed and faster playback. (the "transposition" seems related to buffer size (--buffer 4096 vs 2048 etc.), note that the samplerate of the audio device was set to the same as the sound file (44.1kHz).

2) I used the following 'trick' to first retrieve the names of the coreaudio driver registered to the system and then choose one for playback (as described by Chris Bagwell in this thread: "Using sox with external audio devices on OSX" on the sox-user list in March 2012).

$sox   -V6 -n -t coreaudio nonexistent

-which returns a list of coreaudio drivers -> amongst them "Fireface 800 (". 

Then I tried playback using the Fireface coreaudio driver like this:

$sox  /Users/Marlon_MBPro3/drumLoop.aif -t coreaudio "Fireface 800 ("

Which yielded identically sounding (distorted) output.
Using the MOTU 828 MK2 in the same way I had similar results.

Then, I tried using virtual/internal audio drivers for MacOs such as Jack ( http://www.jackosx.com ) and Soundflower ( https://github.com/tap/Soundflower ) as I described in that same thread before. Using soundflower and soundflowerbed to route it to the audio device the audio seems ok in terms of pitch/speed, however there are intermittent crackles in the individual channels.

I tried this with different samplerates, wordlengths etc. and don't really know what to do anymore at this point. Can anyone reproduce this or perhaps recommend a fix or workaround? Could it for example be related to interleaved/non-interleaved multichannel audio? I'd *greatly* appreciate any hints since I would like to use sox for teaching purposes in a multichannel studio environment...

My apologies in case I sent this mail to the wrong list, I assumed this might rather be a topic of interest for developers.

Many thanks,
Regards,
Marlon







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