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a pointer to improved resampling and other potentially useful programs
#1
Frank Luebeck, a member of the German forum aktives-hoeren (active listening), has discovered, that the sox does not use the full capabilities of the resampling routines in libsoxr. Those are capable of handling 64 bit samples, while input in sox is limited to 32 bit samples. Hence he has written a program resample-soxr that works with 64 bit samples. In addition, he has written other very useful programs for improved audio quality, see http://137.226.152.76/frankl/stereoutils/player.html and https://bitbucket.org/frank_l/frankl_stereo/. Some people claim to have used them in combination with squeezelite and with MPD to good effect.

Especially for resampling, it would be nice to know the base frequency before determining the resampling factor; resampling 44.1 kHz material to 192 kHz may not be the best choice, 176.4 kHz would be better. Daphile has such a capability (but it is based on squeezelite). In MPD-based players this was thought to be impossible, since only the audio stream is piped, not the information about the current bit rate. While I'm not a programmer, the discussion with Dimas Sky on https://bitbucket.org/frank_l/frankl_ste...t-47497909 seems to suggest that the technique of parameter substitution could help to get around this problem.

-- Jürgen
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#2
Hi,

There are a couple of posts in the MPD Github regarding SoX recipes and auto-resampling based on input rate.. Below is one off them. MaxK has tagged them as [features] which suggests that will eventually become part os MPD itself.
https://github.com/MusicPlayerDaemon/MPD/issues/122
Enjoy the Music!
moodeaudio.org | Mastodon Feed | GitHub
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#3
Good to know that the MPD developers are aware of this shortcoming and seem to be working on it. No need to provide a band-aid in each application.

-- Jürgen
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#4
There is a way to re-sample outside of mpd... using hardware up-sampling instead of software re-sampling.
Takes the overhead to a dedicated chip...works very well with Ess Dacs to up-sample to 256-DSD and bypass the Ess internal filters.... Cool

This device... tested and works with MoOde... either i2s or usb to i2s.... Smile

https://www.ebay.com/itm/AK4137-I2S-DSD-...SwUPZbNPYv

even a hat....
https://www.ebay.com/itm/Raspberry-Pi-2B...Swf95bgRYm

and a biggie with spdif in....
https://www.ebay.com/itm/HIFI-AK4137-DAC...2321488069
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bob
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#5
(09-26-2018, 08:09 AM)DRONE7 Wrote: There is a way to re-sample outside of mpd... using hardware up-sampling instead of software re-sampling.
Takes the overhead to a dedicated chip...works very well with Ess Dacs to up-sample to 256-DSD and bypass the Ess internal filters.... Cool

This device... tested and works with MoOde... either i2s or usb to i2s.... Smile

https://www.ebay.com/itm/AK4137-I2S-DSD-...SwUPZbNPYv

even a hat....
https://www.ebay.com/itm/Raspberry-Pi-2B...Swf95bgRYm

and a biggie with spdif in....
https://www.ebay.com/itm/HIFI-AK4137-DAC...2321488069

I'm curious about the second one. How would I use it? I plug it into my RPI and then how do I connect it to my USB/SPDIF DAC? Thanks!
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#6
They are I2S output .
What is the make and model of your DAC ?
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bob
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