"I added support for reading DSF and DFF files to SoX and figured someone here might find it interesting. The source code is at https://github.com/mansr/sox.
With these additions, converting to PCM is a simple matter of invoking the "rate" filter. I have tested it with DSD64, DSD128, and DSD256 in stereo and multi-channel. The output seems entirely satisfactory to me, though I haven't done any thorough comparisons to other converters." (mansr)