I’m sure there are tons of posts about this…
But i’m quite confused, and a starting point would be helpfull.
questions:
-if a got it right, DSD is the audio codec for SACD (and should support also multichannel)
-DSF is the same thing, but slightly different to allow tags
-Roon can handle DSD/DSF files. but… do you need a DSD endpoint? For example, my DAC (squeezebox touch) is not. And i’ve seen in the signal path that a DSF album just upoloaded is converted to PCM
-if i convert the DSD to PCM with another program (e.g. foobar), is this convertion lossless? i mean, can i go forth and back from DSD to flac like i do from (e.g.) APE? or is there more to it like a resampling? if this is so, it’s better to keep the DSD files and let roon do the conversion (in case of a future DSD capable DAC…)
-last question: for some reasons, you can download SACD as .ISO files. that is not read by roon. but there are tools to extract from ISO to DSD. is this conversion lossless?
DSD is the commercial name for digital audio encoded with 1 bit at sampling frequencies that are multiples of 2.8MHz. There are two major file formats that store DSD audio: DFF (i.e. DSD Interchange File Format, or DSDIFF) and DSF (i.e. DSD Stream File).
DFF was designed mainly for SACD mastering, so it can contain one or more tracks and also supports compression, but it doesn’t “natively” support rich metadata. You can store single tracks in DFF files and there are ways to embed ID3 metadata, but that’s not very popular.
DSF is a “consumer” format for storing single DSD tracks and has support for ID3 metadata, so I guess that’s what makes it most popular.
SACDs are physical discs that store DSD audio at 2.8MHz. Just like CDs, they don’t store “files” internally. Also, the hi-def layer can have two regions, one stereo and one multi-channel. When ripping such a disc, it’s convenient to rip both regions into one ISO file, then extract individual DSF or DFF tracks (either stereo or multi-channel) from the ISO at a later time. This extraction is lossless, as it preserves the original bits on the disc.
You can play back a DSF or DFF file without conversion on a DAC that supports DSD, either natively or as DoP. If the DAC doesn’t support DSD, audio will be converted to PCM. This conversion is not lossless, since there is down-sampling involved (from 2.8MHz down to say 352.8kHz). Conversion from PCM to DSD is also not lossless, since that involves up-sampling and bit reduction to 1 bit.
In general, you should keep whatever format you downloaded and let Roon do all the required processing during playback.