Server Version#: unsure, latest as of 6/25/2021 .
Player Version#: 1.33.0.2444
I am having a problem with audio passthrough. I am using an old Yamaha RX-V420RDS receiver with optical audio input. My PC has an MSI B550 MS-7C56 motherboard with an AMD 4650G APU. I am using the Realtek SPDIF optical audio output from the motherboard with the Realtek drivers from the MSI motherboard support page.
I can output Dolby Digital 5.1 just fine from the Windows sound test, as well as DTS. JRiver Media center also has no problem bitstreaming DD or DTS with video files I downloaded. Kodi 19.1 for Windows with the Plex video add-on also has no problem doing Dolby Digital 5.1 bitstreaming to my receiver.
However, when I play movies using either Plex for Windows, Plex Media Player for Windows, or Plex HTPC for Windows, I get PCM stereo only when I select movies with a Dolby Digital 5.1 / EAC3 soundtrack. If I select an AC3 soundtrack. Bitstreaming does work if I select a DTS soundtrack.
In Plex for Windows, I enabled passthrough for both Dolby Digital and DTS. But only DTS bitstream works, not DD.
It looks like a bug in the Plex applications for Windows. Is there any way to get this bug fixed ? I realize I’m using an old receiver, but this is a brand new AM4 motherboard, and I was expecting the SPDIF to work properly.
Dolby Digital Plus bitstreams are not directly backward compatible with legacy Dolby Digital decoders. However, Dolby Digital Plus is a functional superset of Dolby Digital, and decoders include a mandatory component that directly converts (without decoding and re-encoding) the Dolby Digital Plus bitstream to a Dolby Digital bitstream (operating at 640 kbit/s) for carriage via legacy S/PDIF connections (including S/PDIF over HDMI) to external decoders (e.g. AVRs, etc.). All Dolby Digital Plus decoders can decode Dolby Digital bitstreams.
So, I would say it’s still a bug in the Plex for Windows clients. Especially since the same EAC3 movies only play in stereo with Plex clients, but play in 5.1 with Kodi on the same machine with the Plex add-on.
And actually 192 kHz stereo PCM 24 could fit in an SPDIF optical channel. And that’s 9.2 Mbit/s which is more than EAC3 at 6.x Mbit/s.
Of course this very old RX-V420RDS receiver my mother is using doesn’t support DD Plus, and even with PCM only supports 48 kHz. I guess no receiver implemented DD Plus with SPDIF since HDMI came along, but it would have been technically possible to do so. SPDIF coax probably wouldn’t have worked, though.
