Tanix TX6 SPDIF passthrough

bikike · November 7, 2021 at 5:09 PM

Hello All,

first of all my appreciation for the great work on this. I run LibreELEC and updated http://jernej.libreelec.tv/test/passthrou…857-6a2c1ea.tar on a Tanix TX6. I attached my AVR via a digital coax cable to the TX6, Unfortunately I can only choose sound output via HDMI, which does not work for me.

Any hints how I can enable SPDIF output?

Thank you for your help

**chewitt** · November 7, 2021 at 5:25 PM

Quote from bikike

Any hints how I can enable SPDIF output?

Start by writing the dw-hdmi kernel driver code to support S/PDIF output. Finish by connecting the cable. Add "lots of dev stuff" in the middle

**Da Flex** · November 7, 2021 at 5:44 PM

Quote from chewitt

Start by writing the dw-hdmi kernel driver code to support S/PDIF output. Finish by connecting the cable. Add "lots of dev stuff" in the middle

What he is trying to say: Buy an HDMI audio extractor, or a USB sound card.

**jernej** · November 7, 2021 at 5:51 PM

chewitt Da Flex H6 SoC has separate SPDIF peripheral and thus Tanix TX6 board has SPDIF connector. However, it's not enabled because I can't test it.

bikike I can prepare test image for TX6 with SPDIF enabled, but it doesn't support passthrough (at least for now). It would be separate effort, this one is about HDMI passhtrough.

bikike · November 7, 2021 at 6:39 PM

jernej A test image would be nice indeed. I more than happy to test it, when ready. I want to be able to listen to sound via amplifier and speaker system rather than my TV, which has no option to send audio out. If post does not belong here, please move to appropriate thread.

Thank you

**jernej** · November 7, 2021 at 8:21 PM

bikike Here is TX6 test update with enabled SPDIF: http://jernej.libreelec.tv/test/tx6-spdif/ Please report if it works. Passthrough shouldn't be that hard to make it work from programming standpoint, but I don't have proper equipment for testing, which complicates situation very much.

bikike · November 8, 2021 at 6:46 AM

jernej : Just rebooted with the test update. In Settings > System > Audio no difference from before: Visible are Alsa HDMI devices and Pulse Bluetooth device. In the console alsamixer F6 shows me allwinner-hdmi as only device. Which log would I search for the output we are looking for?

**jernej** · November 8, 2021 at 5:14 PM

Strange. I can reproduce issue on my box but I have no clue why card is not exposed. I'll look into it.

**jernej** · November 8, 2021 at 5:47 PM

bikike try now (same link). One driver wasn't enabled. If it works for you, I'll open PR.

bikike · November 8, 2021 at 6:31 PM

jernej Thank you a lot.

It works : Just rebooted with the updated update. I chose SPDIF as output, amplifier is connected via digital coax cable to SPDIF of TX6. 5.1 sounds like it supposed to sound. I will give it a more thorough test later.

**jernej** · November 8, 2021 at 6:49 PM

Quote from bikike

5.1 sounds like it supposed to sound.

Are you sure? SPDIF core supports only 2 channels max., so you should get downmixed stereo sound, unless if passthrough stayed enabled from your previous experiments and your AVR detects compressed audio even if metadata tells otherwise.

**chewitt** · November 8, 2021 at 6:59 PM

S/PDIF supports 2-ch but if you configure pass-through and pack those channels with IEC958 frames correctly you get 5.1 audio.

bikike · November 8, 2021 at 7:15 PM

jernej and chewitt :You are both right. My amplifier still was on 5.1 setting. Changing it's setting to autodetect gives me 2-ch plus subwoofer. While passthrough is not present in Settings > System > Audio, I can enable it in the audio settings in the movie player.

Still experimenting with the settings. Already a big improvement to the built in speakers from my TV, though

**jernej** · November 8, 2021 at 7:19 PM

Passthrough should be easy to support here. I just need to figure out how to add control and how to copy content from control to registers. After that, I can make passthrough setting visible again, although HDMI passthrough would still be hit or miss.

**jernej** · November 8, 2021 at 7:24 PM

bikike can you show me what kind of cable you're using for SPDIF? I can't find anything useful on web shops. Maybe I'm using wrong keywords.

bikike · November 8, 2021 at 7:33 PM

https://i.ebayimg.com/images/g/W08AAOSw4CxhgfMM/s-l1600.jpg

Not meant to be an ad, just for illustration purposes

**jernej** · November 8, 2021 at 9:07 PM

I went through SPDIF core description and I believe I can add support for non-linear PCM a.k.a compressed audio without too much trouble. I'll ping you here when test update will be ready.

**jernej** · November 9, 2021 at 4:59 PM

bikike Please test this update: http://jernej.libreelec.tv/test/spdif-pt/

I added things needed for SPDIF passthrough to work correctly.

Notes:

1. enable at least advanced settings mode in order to see audio passthrough settings

2. high bitrate formats are not supported (TrueHD, DTS-HD, ...)