01-14-2024, 01:21 AM
(01-13-2024, 10:23 PM)Doc77 Wrote:(01-13-2024, 09:49 PM)Tim Curtis Wrote: DoP is where DSD format is packed on-the-fly into PCM frames that contain a special "DoP flag" that tells the DAC to unpack the frames and send the bits to the DSD processing section on the chip.
The DoP PCM formats are:
DSD64 -> 24 bit / 176.4 kHz
DSD128 -> 24 bit / 352.8 kHz
If you see 32 bit instead of 24 bit its because the DAC only accepts 32 bit word length. In this case 24 bit is simply zero-padded to 32-bit. The original 24 bits of data are left untouched.
Exactly as you see in the attached screenshots. The only difference, as we have already said, is that by selecting Dop, I have no sound (i2s only pcm..)
But from DSD 1bit I don't get PCM 176.4 khz, but PCM 352.8 Khz?!?! The .dsf file is the same DSD 1 bit 2.822 Mhz: this is a DSD64 or DSD128 ??
Is this normal?
Many thanks @Tim Curtis
Here is the (i) help for MPD DSD support option. I've added more info below each of the options to help explain whats going on.
Native DSD: If the audio device reports that it supports Native DSD then MPD will send the unaltered DSD bitstream to the device otherwose MPD will perform DSD to PCM on-the-fly conversion.
For DSD to PCM on-the-fly conversion, the PCM rate thats sent is determined by MPD and ALSA, is a multiple of 88.2 kHz up to the max rate the audio device supports. For I2S DAC's the max rate is 384 kHz and thus DSD64 is sent at 352.8 kHz, DSD128 and above will be sent at 384 kHz. IIRC for USB DAC's that support higher PCM rates the on-the-fly rates for DSD128 and above will be higher multiples of 88.2 kHz.
DSD over PCM (DoP): There is no way to detect if an audio device supports DoP so only enable this if you are certain that the device support it otherwise the encapsulated DSD bitstream may cause loud or unpredictable distortion.
The DoP spec stipulates:
DSD64 has to be sent as 24 bit / 176.4 kHz
DSD128 has to be sent as 24 bit / 352.8 kHz