HDMI to AVR bitstream


In playback options i set the signal to go as DSD Direct. My avr, Marantz SR6012 supports all sorts of audio formats. I am not sure why it is receiving signal as PCM instead of Bitstream.
I dont seem to get bitstream to my AVR. I would like my AVR to decode all audio.

Is bitstream not implemented in Volumio?

I have RPi 3 B+, audio over HDMI to AVR.
I am using Radio Paradise plugin and flac stream.
I am also playing my flac files from NAS.