HDMI Multichannel Audio: Channel layout incorrectly identified

Help and Support
1

Firstly - congratulations to the Volumio team for the product evolution to Volumio3. Well done.

I searched the FAQ’s first and could not find this issue reported.

Short Description: Multichannel audio played through HDMI is always mapped as 7.1 channels (3.4.1). Additionally, Side L/R channels in 4.0 and 5.1 are incorrectly mapped to Rear L/R channels.
7.1 content plays correctly. :slightly_smiling_face:

More details:

  • 2 channel stereo content is correctly rendered
  • Multichannel audio plays without issue but 4.0, 5.1 and 7.1 content is always rendered as 7.1 channels
  • I have tested various file containers (flac, wav, dsf, etc) but the result is always the same
  • I have verified the channel layout of the audio files with the MediaInfo tool
  • in testing, playback was via the network through a dlna server (AssetUPnP) and direct file playback from a QNAP NAS (ethernet connection)
  • Volumio3 (v3.173) is installed on a Raspberry Pi 4 (4Gb)
  • Playback device is a Marantz SR8015 AVR
  • I have confirmed correct rendering and playback of the same source materials on the Marantz AVR using an Oppo 105D. 4.0, 5.1 and 7.1 content plays back with correct channel mapping using the same HDMI port and cable. The AVR also reports the correct channel layout

I have posted some fundamental terminal output below and would be happy to provide additional information as needed.

Thanks again for a great product!

volumio@volumio3:~$ tvservice -a
     PCM supported: Max channels: 8, Max samplerate: 192kHz, Max samplesize 24 bits.
     AC3 supported: Max channels: 6, Max samplerate:  48kHz, Max rate  640 kb/s.
     DTS supported: Max channels: 6, Max samplerate:  96kHz, Max rate 1536 kb/s.
    EAC3 supported: Max channels: 8, Max samplerate:  48kHz, Max rate   24 kb/s.
   DTS_HD supported: Max channels: 8, Max samplerate: 192kHz, Max rate    8 kb/s.
     MLP supported: Max channels: 8, Max samplerate: 192kHz, Max rate   24 kb/s.


volumio@volumio3:~$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: b1 [bcm2835 HDMI 1], device 0: bcm2835 HDMI 1 [bcm2835 HDMI 1]
  Subdevices: 4/4
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
card 1: Headphones [bcm2835 Headphones], device 0: bcm2835 Headphones [bcm2835 Headphones]
  Subdevices: 4/4
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3


volumio@volumio3:~$ alsacap
*** Scanning for playback devices ***
Card 0, ID `b1', name `bcm2835 HDMI 1'
  Device 0, ID `bcm2835 HDMI 1', name `bcm2835 HDMI 1', 4 subdevices (4 available)
    1..8 channels, sampling rate 8000..192000 Hz
    Sample formats: U8, S16_LE
    Buffer size range from 80 to 131072
    Period size range from 80 to 131072

      Subdevice 0, name `subdevice #0'
      Subdevice 1, name `subdevice #1'
      Subdevice 2, name `subdevice #2'
      Subdevice 3, name `subdevice #3'
Card 1, ID `Headphones', name `bcm2835 Headphones'
  Device 0, ID `bcm2835 Headphones', name `bcm2835 Headphones', 4 subdevices (4 available)
    1..8 channels, sampling rate 8000..192000 Hz
    Sample formats: U8, S16_LE
    Buffer size range from 80 to 131072
    Period size range from 80 to 131072

      Subdevice 0, name `subdevice #0'
      Subdevice 1, name `subdevice #1'
      Subdevice 2, name `subdevice #2'
      Subdevice 3, name `subdevice #3'
2

I don’t think there was ever any promise to support multichannel.
Volumio focusses on 2-channel audiophile output.
Also doubt whether you will get a lot of response on this topic, perhaps google the raspberry forums for more info on MPD and multichannel output.

3

Thanks @gkkpch, appreciate your response.
I posted similar information during the volumio3 beta phase but got no response there either.

You do raise an interesting point. I went back and looked at the official Volumio webpage.
I could not find any reference to Stereo / 2 channel only. The description below is the official definition.
“Volumio is an open source Audiophile Music Player. It is designed to play all your music in high quality from any device with a browser.”

I would be nice to hear from the volumio team on this topic. Is multichannel audio expressly excluded from the product scope?

4

The answer is yes, 2-channel stereo is what we guarantee.
I can speak for the x86 version, where I do not support HDMI or SPDIF with more than 2-channel stero. When some hw configurations have working multichannel, than that is a bonus but remains unsupported.

Note the term audiophile, audiophiles only discuss 2-channel stereo.
All the HiFi DACS being produced, the HiRes music formats, all of it is 2-channel stereo.

5

Thanks @gkkpch . . . that clears that up.

Who knows, adding multi-channel support as a paid tier might create some additional revenue for Volumio in the future. It is something I would be willing to pay for.

For now, I will need to improve my knowledge of Custom ALSA Contributions and experiment (a lot). :slight_smile:
Ciao

6

I don’t want to destroy your hopes.
But there is no demand for it and it is very unlikely Volumio is going to assign resources to things that do not add to the audiophile world experience, paid tier or not.
As explained, Volumio’s prime interest is 2-channel stereo.

7

Out of interest, from where do you even find music with more than 2 channels?

8

Oh, there are plenty. I have a few .mkv’s extracted from multichannel DVDs, not HiRes but plays down mixed (by mpd?) to 2-channel just fine.

1 Like
9

Sorry for the very late reply to this. SACDs for example, not all of them but many come with 5.1 (or more) multichannel audio files. There are even some which feature new mixes, like for example David Bowie’s Heathen, and they do sound much better than the stereo counterpart. In some cases they are uncompressed and a real treat to listen.

10

Yeah, I think defining ‘audiophile’ as stereo only may be out of step. Atmos, Auro3D are examples of the new generation of listening. Many new boxsets come with 5.1 and Atmos mixes. All the streaming services are offering multi-channel now too.
Anyway, Volumio gets to decide who its audience is and I can respect that.

11

Thanks for bringing this to our attention.

Even if we don’t want to define what is “audiophile” or what is not, simply there is not enough demand for us to prioritize this scenario… sorry…

12

I just found this thread looking for a solution of multichannel audio on Volumio.

First of all, I would like to say that I really like Volumio and that I appreciate all the hard work behind this project.

That said, multi-channel audio is one of the most interesting aspects in hi end audio right now. Just think of linear phase crossovers + multiple sub optimization - all of which can be now be run in RPis running Volumio - and you will see that actually muti-channel audio might offer extremely interesting capabilities.

I think opening the door for multichannel output and multichannel DSP plugins would be one of the most intelligent developments of this platform, particularly if aimed at audiophiles.

2 Likes
13

Thanks @madera for adding your voice to this. You highlight some amazing possibilities that extend beyond my simple channel mapping issue.

14

there are HiRes! and DSD! no hassle - even DolbyAtmos(Tidal)

15

hi, how do I make Tidal output atmos. I only get stereo on my receiver .
thansk.

16

Just signed up here to provide my thoughts. This is a feature I would pay for. I think it’s a wasted opp to not support multichannel when any Raspberry Pi has an HDMI port right there, capable of passing uncompressed multichannel audio to an HDMI receiver. I’m looking for a way of sending multichannel flac audio to my receiver, which can be positioned nearby my receiver. It makes perfect sense to use it as a networked receiver.