I have been playing with SOX upsampling via Squeezelite - all going well
except...

My current project has a Beaglebone Black feeding a miniSHARC DSP via
I2S using the Botic drivers developed by miero. After some
experimentation I have this working. As most of my files are CD images
44.1k the BBB is upsampling to 48k internally as it has only a single
clock. To avoid the BBB doing the upsampling I am trying upsampling via
SOX (assuming it to be superior to the BBB native upsampling) using the
-u startup parameter and -r to set max sample rate. To test this is
working I tried with -r 96000 and displayed via 

cat /proc/asound/BOTICAudio/pcm0p/sub0/hw_params

However this is showing a rate of 48000 rather than the expected 96000.


access: MMAP_INTERLEAVED
format: S32_LE
subformat: STD
channels: 2
rate: 48000 (48000/1)
period_size: 1024
buffer_size: 16384

So I really do not know if SOX is upsampling from 44.1k or if its the
BBB. If SOX is upsampling then why only to 48k?

The startup I am using looks like this:

squeezelite -o hw:CARD=BOTICAudio -n Botic96 -a 16384:1024:: -u mIX -r
96000 -z

Even tho it only shows a 48k stream it does seem to be getting thru to
the miniSHARC. The miniSHARC can run at 48k or 96k, I have it running
the 96k SW. I have also tested running from the BBB directly to a ES9023
DAC via I2S/Botic drivers and I get the same 48k. All I can think is
some restriction/effect of the Botic driver or maybe the -a startup
param which I had to have for these drivers (earlier conversation with
Adrian).

As a control test I tried all this on a RaspberryPi running I2S directly
to a ES9023 DAC, with the -r set to 192000 it displays as having a 192k
data stream.

Any suggestions gratefully accepted!


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