PC over HDMI to TV over S/PDIF to amp: is transcoding to multichannel DD possible?

    Apologies for the somewhat cryptic title. I have a notoriously old setup with a 10 year tv and a beasty 25-year old (!) Yamaha A2 amplifier. Up to some days ago, my needs in the living room were served by a (also old) AMD-based pc that was equipped with an optical output. Setup worked like a charm: video was sent to the Panasonic 50" plasma over HDMI and LE was configured to transcode anything multichannel to 5.1 DD (amp also is 5.1 DTS capable).

    The rig went dead and was replaced with a rather cheap Dell optiplex 3050 ultra small form factor thingie, lovable to watch :) I migrated my LE setup to the new box and everything works perfectly (plus having a UEFI boot).

    Problem is that it lacks an optical digital out. Luckily the Panasonic behemoth comes with an S/PDIF out which, at least, makes sure that I can get excellent audio ... albeit in stereo.

    Now I'm certain that it is not doable, but have to ask: is there some sort of "magic" that can be used to send multichannel audio to the TV and have the TV just pass the audio to the amp. From what I've tested this does not work. Still, I'm asking just in case it can be made with some sort of tinkering.

    For what this is worth, I'm looking into workaround. So far:

    * buy some sort of HDMI splitter boxes that take HDMI and output both HDMI and S/PDIF: work but a bit pricey

    * was looking into whether small form factor PCI cards with S/PDIF exist, until I found out that the Dell has no room for cards at all

    * currently checking whether I can get a USB card that also has S/PDIF without spending a fortune

    * will look whether there's some sort of Dolby ProLogic transcoder for Kodi exists: if it does I'll simply transcode everything multichannel to the special stereo signal for ProLogic.

    Please free to suggest any inexpensive solutions (if any) :)

    Quote from Da Flex

    Seems like your Panasonic S/PDIF can only deliver stereo. So get an HDMI audio splitter with TOSLINK. It's not too expansive.

    Digging around in the tv documentation and making a few tests seems to indicate that the tv s/pdif can also send DD multichannel, albeit from TV stations only (and not from HDMI inputs) :(

    For the record, I did find an oooold addon that did conversion to analog Dolby ProLogic. Unfortunately it's a no go for recent Kodi versions. Would be nice to test though.

    As for HDMI splitters: they are tried and tested but IIRC when using them with RPi's there were some issues with the correct transfer of EDID information.

    Quote from petediscrete

    Something like this would probably fit the bill https://www.amazon.co.uk/Cubilux-TOSLIN…600288957&psc=1

    That's awesome, especially since it seemed it worked fine on Linux, considering the comments! Pity it's not available for purchase :( Could you provide any alternatives to that. I live in Greece, so everything from amazon.de (.fr/.it/.es) could be purchased easily.

    Funny thing is that I've been searching and searching in aliexpress for example and could not find anything (apart from expensive DACs and HDMI splitters).

    Quote from cosmos

    Digging around in the tv documentation and making a few tests seems to indicate that the tv s/pdif can also send DD multichannel, albeit from TV stations only (and not from HDMI inputs) :(

    I also have a Panasonic Plasma, just with TOSLINK instead of electrical S/PDIF. Works fine with my DD / DTS AVR. So I pretty much have the same setup like you. I go RPi HDMI -> TV and TV TOSLINK -> AVR. That should also work for S/PDIF.

    Quote from Da Flex

    I also have a Panasonic Plasma, just with TOSLINK instead of electrical S/PDIF. Works fine with my DD / DTS AVR. So I pretty much have the same setup like you. I go RPi HDMI -> TV and TV TOSLINK -> AVR. That should also work for S/PDIF.

    Don't bash me please, but isn't S/PDIF the same with TOSLINK? :angel:

    Indeed this is a TOSLINK (optical) interface and not a coaxial. My tv model is (again IIRC) TX-P50UT50E, dated 2012ish or something.

    Connection of my Dell to the TV is made over the non-ARC HDMI. And from TV over toslink to the Yamaha A2.

    In your setup are you able to pass-through DD 5.1 data from the RPi to the TV and then to the amp? Whenever I try that I don't get any sound at all on the other end.

    AFAIK RPi does nothing special compared to a pc, apart from doing CEC and stuff (which should not be relevant in this case at all). What sort of debugging from SSH could I do to check things up? I really hope that having a similar TV/setup you might be able to help me out.

    In the meantime I was looking solutions from aliexpress like these one, but don't know if they do the trick:

    * https://www.aliexpress.com/item/32955530378.html

    * https://www.aliexpress.com/item/4000244824209.html

    <off topic>Who should I contact to check why I do not get email notifications on thread answers (even though the relevant option is enabled)? </off topic>

    Edited 2 times, last by cosmos: minor correction (April 16, 2023 at 8:51 PM).

    Quote from cosmos

    In your setup are you able to pass-through DD 5.1 data from the RPi to the TV and then to the amp? Whenever I try that I don't get any sound at all on the other end.

    Yes. Start problematic audio on your LE box. Then hit the menu button of your Panasonic RC. Go to Sound. You'll see an entry HDMI<NUMBER>. Switch that option to "Digital".

    That's correct. Specifically, it shows up as ALSA device HDA Intel PCH, MEI Panasonic-TV on HDMI #0. I'm using the same device as the passthrough device as well. I'm posting my audio setup (sorry if it's all Greek to you :D ).

    With the posted settings I get audio only on 2.0 sources (IIRC). Furthermore, with passthrough enabled in Kodi and with multichannel sources, when I press "O" to show playback information it shows that the source audio is "RAW, RAW, RAW..." etc, instead of "FL, FR, ..."

    This is the same setup that I'm using.

    Sometimes I get "Dolby Digital" output from a TV channel, so Panasonic TOSLINK is capable to transmit DD / DTS to the AVR.

    Check this: When your LE box is off, go to TV's sound menu, and set "SPDIF Selection" to "Auto".

    Quote from cosmos

    As for HDMI splitters: they are tried and tested but IIRC when using them with RPi's there were some issues with the correct transfer of EDID information.

    Hi, just some additional info about the "issues with the correct transfer of EDID information". Can be resolved by saving the EDID data without the HDMI splitter. After that the LE always will load the saved EDID and the HDMI splitter can be used. Use the "getedid create" command (More info).

    Quote from Da Flex

    Check this: When your LE box is off, go to TV's sound menu, and set "SPDIF Selection" to "Auto".

    Problem is that under the tv sound options, Audio Preference and SPDIF appear solely when viewing tv and not when switched to HDMI #1. Upon closer inspection, in the manual ( https://www.manua.ls/panasonic/tx-p50ut50e/manual?p=41 ) it is stated that:

    Quote

    (with regard to the DIGITAL AUDIO OUT and HDMI2 (ARC function) terminals

    [...]

    * For DVB mode or video contents of Media Player / Network services

    ...

    Which prolly means I'm screwed here :) No way to send DD from an HDMI source to optical. Probably Panasonic understood its bummer and evolved this functionality in more recent tv sets (as yours, I presume)...

    VLouis thanks mate, yes I am aware of the steps needed. Cost was off-setting me TBH, and the solution proposed by petediscrete would definitely be preferable. Will continue looking for a USB-to-Toslink 5.1 solution.

    If only I could get rid of my Yamaha and B&W speakers, I'd go for an HDMI soundbar and get done with it :)