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Author Topic: Support for DSD Convolution  (Read 2518 times)

HiFiTubes

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Support for DSD Convolution
« on: June 23, 2013, 05:40:13 am »

Implemented by Signalyst, would be welcome addition to the MC toolbox.
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Hendrik

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Re: Support for DSD Convolution
« Reply #1 on: June 23, 2013, 05:45:08 am »

After reading that thread you linked, other than that one app doing it without giving technical details, the consensus seems to be that for processing you need to go PCM, which is also what i understood on the general concept of DSD.
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~ nevcairiel
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Matt

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Re: Support for DSD Convolution
« Reply #2 on: June 23, 2013, 12:07:03 pm »

You can't do sample-based DSP in any meaningful way on a 1-bit signal, as least that I have ever seen or can conceptualize.

You have to switch to some intermediate format and back.

If JRiver did this, the intermediate format would be something like 64-bit / 352.8kHz (an 8x data rate expansion), so I suppose you could argue the processing was "native."  However, that's just an issue of semantics, and a silly one at that.  There's nothing magical about DSD or PCM.

Regardless, the ability to output any audio as 1x or 2x DSD is planned for the future.  The argument is that it could work better with certain DACs.
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Matt Ashland, JRiver Media Center

HiFiTubes

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Re: Support for DSD Convolution
« Reply #3 on: June 23, 2013, 11:44:53 pm »

Thanks Matt and Nev; this is in line with my thinking, especially the "DXD expansion" you mentioned Matt. However, Jussi at Signalyst is no slouch and I feel he could be on to something. He claims it can be done.

Quote
"If Acourate can export filters in WAV format you can use those. WAV needs to be mono per channel, but stereo WAVs are easy to split to mono ones.

Since PCM filter WAV is by necessity bandwidth limited, I have implemented "HF-expand" option for expanding the filter as flat above it's Nyquist frequency. However I recommend using as high as possible sampling rate for the filter WAV. If 352.8/384k is possible, then things would work pretty nicely without "HF-expand" too. And it's not bad with 176.4/192k either.

To enable DSD processing HQPlayer you need to un-check the "Direct SDM" box in "DSDIFF/DSF Settings" -dialog. Then you can perform DRC and also multichannel speaker distance and level adjustments plus main digital volume control. For any processing I recommend using max -3 dBFS main volume setting to avoid overloads. Overloads in DSD are more nasty than in PCM.

When source is DSD and output mode is DSD, DRC processing is performed at native source rate. You can combine it with per channel level and speaker distance adjustments plus global digital volume control, performed at native target rate. IOW, you can decide to resample. So usually when I play DSD64 content, I perform DRC and some level adjustments and output at DSD128 rate. DACs like exaSound E20 allow performing DSD64 -> DSD256 upsampling combined with processing. But you can also play DSD128 -> DSD64 if necessary.

If source is DSD and output mode is PCM, then DRC processing is performed in PCM at 1/16 rate after conversion."
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