Re: Problems converting from DSD128 to DSD64

["Måns Rullgård" <mans@mansr.com>]

Michael Vernersen <michaelvvv@gmail.com> writes:

>> On 2017-08-27 15:53, Måns Rullgård wrote:
>>> Michael Vernersen <michaelvvv@gmail.com> writes:
>>>
>>>> Hi.
>>>>
>>>> Tried to convert from DSD128 to DSD64. Convertion went fine
>>>> but not playing on my DAC.
>>>>
>>>> My DAC plays DSD64 DSD128 with DOP without any problems.
>>>>
>>>> Convertion in Sox from 2 Flac works fine.
>>>>
>>>> My cmd I used is the following.
>>>>
>>>> sox -V4 01-DSD128.dsf 01-DSD64.dsf rate -v 2822400 sdm
>>> Looks like you're using my patched version with DSD features.  Could you
>>> explain in some more detail what goes wrong?
>>
>
>
> Jeps , I'm using your version from ARCH AUR
>
> https://aur.archlinux.org/packages/sox-dsd-git/

Hmm, that package really could use an update to the latest version in my
git repo.  There have been some important fixes since it was built.

> When the conversion is done, and no errors here, and I
> try to play the new file , I get 1 sec high frequency noise from my
> DAC chord 2qute and playing stops.

The high-frequency noise in the DSD128 input is destabilising the
modulator.  You need to get rid of it with a low-pass filter.  Something
like this will do:

$ sox dsd128.dsf dsd64.dsf lowpass 50k rate -v 2822400 sdm

For a sharp cut-off, use the sinc effect instead of lowpass.  The exact
frequency isn't important, so you might want to experiment a bit.

-- 
Måns Rullgård

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