White noise playing DSD audio in RPi 3+

[jcucurull]

Hello,

I am having an issue playing DST files (ripped from my own SACDs) in MPD 0.23.14 in my Moodeaudio 9.0.2 system in a RPi 3B+. In my case my AVR does not support DSD natively, thus they are automatically converted to PCM by MPD.

The issue is that when I reproduce a DST file, the song starts playing but on top of it one can hear a strong white noise. This happens both with 2 and 6 channels songs and in all the channels. I have also tested to enable and disable the Thesycon patch but there is no difference.

I have done a few tests and it seems the issue is related to the max rate supported by my AVR, which is limited to 96Khz. MPD automatically adjust the sampling rate to 96Khz when converted to PCM, but it adds the white noise. We done the following tests:

1. We have tested the same DST file with the developers of Moodeaudio in an AVR that supports 192Khz and it worked flawlessly.

2. I have tried to reproduce a 192/24 FLAC file and it was reproduced without any issue. MPD automatically resampled it to 96Khz (the limit of my AVR) without any sound quality issue.

3. I have tried to enable the SoX resampling in the configuration to 96Khz (at 16, 24 and 32 bits) and then the DST file is reproduced without white noise.

From test 3, it seems I could leave the SoX resampling enabled, but I don't think it is a good solution because it does not support multichannel files (and SACDs use to be multichannel) and because it resamples all the audio files, even the ones that are correctly reproduced by default.

Thus, all these tests seem to indicate that the automatic conversion of the DSD to PCM at 96Khz does not work well in my case. Do you have any idea why this might be happening?

I have also opened a discussion thread in Moodeaudio forum: https://moodeaudio.org/forum/showthread.php?tid=6675&pid=55805#pid55805

[jcucurull]

Hello again,

I have realised that is possible to enable the SoX resampling also for multichannel audio just using the "*" in this line:

audio_output_format "96000:32:*"

This solves my issue with DSD playback, at the expense of always resampling to this format, which is the maximum supported by my AVR. Is there a manner to resample only with SoX when the sample rate exceeds a certain rate? (in my case 96Khz)

Still, there is a bug somewhere because this only happened to me with DSD to PCM, if I reproduce a FLAC 192/24 I don't have this issue.