Problem with LFE channel with passthrough via S/PDIF

chook55 · September 12, 2021 at 3:25 AM

RPI4B 2Gb, ARGONONE case. LG ThinQ TV, Marantz SR5500 receiver, Simplecom CM423 HDMI /S/PDIF splitter.

LibreELEC release: RPi4.arm-nightly-20210910-1a8a027

I've done it this way so I can listen to music through the receiver without the TV tuned on.

So this setup has been working well until I had a HDMI cable issue. The cable was not fitting into the connector fully and came away. Resolved eventually by modifying the ARGONONE housing. The TV now reports "Invalid Format" on LibreElec boot, but resolves itself and KODI comes up fine. As this coincided with a nightly update I assumed incorrectly that the card had corrupted or there was a release issue. After much panic I bought a new SD card and burned the latest Nightly 11.0 version on it. I did check the original card and it had faults and I threw it out. I did not have a recent backup so rebuilt my media library from scratch but lost any other settings I may have made over the years.

So here is the problem. Audio is set to 2 channels. Pass-through is on. When playing sample 5.1 tracks the Dolby indicator on the receiver shows it's a 5.1 signal (like a "5" on a dice). So the S/PDIF decoding is working OK. The trouble is the Active Sub woofer is not receiving any LFE sound information.

I suspect when I first configured the new setup I had the HDMI cable plugged directly into the TV and not via the splitter.

Are there some setting I can make in config files to resolve the problem? I OK to send a log if requested.

regards

chook

**Da Flex** · September 12, 2021 at 6:10 PM Official Post

Please do two tests:

- switch pass-through off

- set the amount of output channels to 5.1

chook55 · September 13, 2021 at 12:36 AM

With Passthrough Off and 2 channels set. Best Match. Using DTX and Dolby samples. Receiver shows 2 channels detected and heard. LF and RF. No LFE.

With Passthrough Off and 5.1 channels set. Best Match. Using same DTX and Dolby samples. Receiver shows 2 channels detected and heard. No LFE. Detected by receiver.

The TV receives audio but I cant say I detect any Low Frequency Effects when 5.1 channels are enables. Its subjective but it sounds ab it shallow. I wonder if there is an addon for testing audio channels.

chook

(Australia)

**Da Flex** · September 13, 2021 at 12:54 AM Official Post

Please also test pass-through on and 5.1 output channels.

chook55 · September 13, 2021 at 6:02 AM

With pass-through enabled and 5.1 output channels set, the receiver indicates both DTS 5.1 and Dolby 5.1 signals respectively according to source. These are indicated by a small display on the receiver. The LFE indicator on the Sub-woofer does not illuminate and no speaker activity is heard or felt. When set to manual detect on the sub woofer nothing is heard or felt. I.e the LFE channel is silent.

Unfortunately I have no method of testing an alternate source to validate the LFE channel. I have a separate S/PDIF cable coming from the TV to the receiver via a separate input on the receiver. I can send an optical signal from the TV to the receiver but it currently can only send stereo channels data and the receiver displays only 2 channels received.

chook

chook55 · September 13, 2021 at 12:45 PM

There is a similar thread regarding passthrough with the Release 10 Matrix .

Post

ATMOS pass-through not working after upgrade from LibreELEC (official): 9.95.5 (RPi4.arm) to LibreELEC (official): 10.0.0 (RPi4.arm)

Hi all,

Thought I'd ask this question here in case this is already a known issue and there is a quick fix.

I've been successfully running LibreELEC (official): 9.95.5 (RPi4.arm) since it was released, mainly to get ATMOS pass-through audio and it works really well.

I upgraded to 9.97.1 when it came out and found MKV files with ATMOS stopped opening instantly, when they finally did open after a good 20 second delay no audio was being passed through but video plays, no setting changes were made post…

Shamus

September 10, 2021 at 2:41 AM

**Da Flex** · September 13, 2021 at 1:29 PM Official Post

Yeah, we should dig a little deeper then. Keep audio settings at pass-through / 5.1 output channels, because this seems to fit best.

activate debug logging at GUI (HUD overlay will appear)
reboot
reproduce the error (audio playback)
login by SSH
run pastekodi
post the resulting link

chook55 · September 13, 2021 at 2:07 PM

OK doing it now. I got some blank screens this time.

pastekodi link removed

thanks and good luck.

chook

OK so made a discovery while recording last log.

With 5.1 channel selected as output. ATMOS video will not run properly. For several seconds it stopped playing any sound. No channels appeared active at the receiver. Returning later but locking up.

With 2 channel output the ATMOS video runs OK but still no LFE sound.

The Genesis 4K sample audio plays but the display shows the console view only. IE it doesnt play the video just audio. No LFE sound.

chook

**Da Flex** · September 13, 2021 at 5:59 PM Official Post

This is the critical part of the log:

Code

2021-09-13 22:28:06.359 T:1143     INFO <general>: CAEStreamParser::SyncDTS - dtsHD (core) stream detected (6 channels, 48000Hz, 16bit BE, period: 512, syncword: 0x41a29547, target rate: 0x18, framesize 2080))
2021-09-13 22:28:06.360 T:1143     INFO <general>: Creating audio stream (codec id: 86020, channels: 6, sample rate: 48000, pass-through)
2021-09-13 22:28:06.361 T:1001     INFO <general>: CActiveAESink::OpenSink - initialize sink
2021-09-13 22:28:06.361 T:1001    DEBUG <general>: CActiveAESink::OpenSink - trying to open device ALSA:hdmi:CARD=vc4hdmi0,DEV=0
2021-09-13 22:28:06.361 T:1001     INFO <general>: CAESinkALSA::Initialize - Attempting to open device "hdmi:CARD=vc4hdmi0,DEV=0"
2021-09-13 22:28:06.362 T:1143    DEBUG <general>: CVideoPlayerAudio:: synctype set to 0: clock feedback
2021-09-13 22:28:06.362 T:1143    ERROR <general>: CAEStreamInfo::GetDuration - invalid stream type
2021-09-13 22:28:06.362 T:995      INFO <general>: Skipped 1 duplicate messages..

chook55 · September 13, 2021 at 11:58 PM

What I will do is do a back up on remote storage, reflash the SD card and restore the backup but do so with the HDMI cable connected as is and not directly into the TV as was done for this build. I mentioned earlier I get a message on the TV when rebooting Libreelec saying "Invalid Format" before the LibreElec logo appears. This has only appeared since the last time I built form a reflash and preceding HDMI cable connection issues.

**Da Flex** · September 14, 2021 at 12:00 AM Official Post

The current theory of our internal discussion is that your splitter does something bad to the HDMI signal. Please try again without using the splitter.

chook55 · September 14, 2021 at 2:16 AM

Alas I can not get 5.1 channels to the receiver without the splitter as the LG thinQ TV does not pass 5.1 channels out via S/PDIF only stereo.

The HDMI comes from the RPI to the splitter which has S/PDIF output directly to the receiver and the HDMI (4K capable) goes to the TV. It is possible the splitter was damaged when the cable dislodged from the RPI.

I reflashed with LibreELEC-RPi4.arm-11.0-nightly-20210913-619146d.img and restored the backup. Results..Same.

I'll post a log with the output channels set to 2.

removed

Cheers

chook

**Da Flex** · September 14, 2021 at 3:04 AM Official Post

I think the RPi gets audio capabilities from the TV, not from the receiver. Because the TV has no subwoofer, this makes sense to me.

So the routing should be: RPi -- HDMI --> receiver -- HDMI --> TV.

**Da Flex** · September 14, 2021 at 11:49 AM Official Post

PS: The RPi 4 has two HDMI outputs. To my knowledge, you can use one for TV (HDMI-0), and one for receiver audio (HDMI-1).

chook55 · September 14, 2021 at 12:57 PM

As the Marantz SR5500 receiver has no HDMI input it needs either a digital audio input in via line or optical means or analog input. Prior to the RPi4 being available I have used analog on the RPi1 Rpi2 Rpi3 to listen to music. My older TV could send 5.1data via optical toslink connector and play low frequency effects on the rare occasions a high def movie or was transmitted over the air with 5.1 channels. When I upgraded to the LG OLED TV 2 years ago I had plans on going the same. Only to discover the LG TV does not send 5.1 channels compressed through it's optical out option. It only sends stereo.

So as the early versions of KODI did not have the analog audio working I searched for a solution and found the Simplecom CM425. HDMI2 to HDMI2 and Optical splitter. Its quite affordable and quite capable. As I mentioned before I can listen to music with the TV off or watch a video with DTS ATMOS or Dolby via the KODI system. Until the HDMI cable came out of the RPI box while playing. That connector problem was resolved by opening the metal box to accommodate the cable connector housing. It seems the incident has corrupted something. So what I might do is replace the splitter box with a new one. There is one nearby at about double the cost what I can buy one for online. If the LFE channel still misbehaves I might investigate the audio through the other HDMI port as you suggest.

**Da Flex** · September 14, 2021 at 1:22 PM Official Post

There are "HDMI dummy plugs" available. They can emulate the existence of a TV with many A/V capabilities. So maybe this works:

RPi 4 HDMI-0 --> TV
RPi 4 HDMI-1 --> splitter with HDMI dummy plug --> S/PDIF receiver

It assumes that your current splitter is able to deal with all audio channels. If the splitter is the culprit, this approach can't work.

chook55 · September 15, 2021 at 10:08 AM

Noted. I've been using Simplecom CM425 which is 4K HDMI 2.0 compatible. I've been using it for a while now. Maybe 2 years. I'm looking for a HDMI to audio converter without HDMI out but if I cant find one I'll look for a plug.

I'll do a search through the forums to see what's required to enable HDMI1.

thanks for your time.

chook

**Da Flex** · September 15, 2021 at 5:56 PM Official Post

After dev talk I can say that the audio pass-through is independent of the target device. All available audio channels go out, including LFE.

The HDMI-1 port should send audio without any settings (user reports somewhere on this forum). Because the splitter is very likely the culprit, you don't need HDMI-1. Just replace the splitter.