Problems muxing 6.1, 7 channels audio

[eXtremeDevil]

Hello. I have a 6.1, 7 channels audio that I would like to mux into an MKV. But not matter what I do or how I try (mkvmerge, ffmpeg...) I cannot make the MKV file keep the original 7 channels of the audio, it always "transforms" to a 5.1, 6 channels audio (by looking the result file in MediaInfo).

I've been looking for info on the web, and I ran into this issue: https://gitlab.com/mbunkus/mkvtoolnix/-/issues/2715 (yes, I commented there as well).

On the other hand, I did successfully merge the 7 channels, 6.1 audio into a MP4 and a MT2S container (by looking the result file in MediaInfo). But, when I try to play it (VLC, MPC-HC, Kodi, CoreELEC, PowerDVD...) all the players identify the audio as 5.1, 6 channels instead as a 6.1, 7 channels.

So, is this an ongoing bug, or a known issue about 6.1 audios not being handled by almost any app/player? Even if I managed to get a MKV file with a 6.1, 7 channels audio inside, would any player actually play it as is? Will the players always "transform" it to a 5.1, 6 channels audio?

Thanks in advance!

[eXtremeDevil]

OK, so someone in the GitLab issue conversation suggested to edit the MKV with the header editor and manually set the correct number of channels. And it works, at least according to MediaInfo. After editing the header, the channel count and distribution seems right. But still, none of the players I tested (VLC, MPC-HC, Kodi, CoreELEC or PowerDVD) can play it right, it's always recognized as a 5.1, 5 channels audio. It is also recognized as 5.1 by LAV splitter.

[oniiz86]

@eXtremeDevil Since the Header Editor has not worked, you may have some luck with demuxing the DTS ES 6.1 audio track using UsEac3to v1.3.4 then re-mux with MKVToolNix, this has worked for me very successfully when I've come across problematic DTS ES 6.1/DTS-HD MA 6.1 audio tracks within a mkv container.

[eXtremeDevil]

I have the audio already demuxed, it is DTS extension and the channel count is correct according to MediaInfo. I will try what you say and see what happens.

Yep, same results. Eac3to logs shows the audio as 5.1. The demuxed audio is 6.1 (according to MediaInfo). If opened with MkvToolNix, reports as 5.1.

In any case, as I said, I successfully muxed the audio into a MP4 and M2TS containers, where the audio seems to keep the 6.1 properties, BUT, all the players I've tried reports the audio as 5.1. Is it an issue with this audio, or do the players have problems decoding 6.1 audios?

[tebasuna51]

Upload samples.

[eXtremeDevil]

Upload samples.

Here it is, a 1 minute sample of the 7 channels audio, trimmed with ffmpeg (codec copy):

https://mega.nz/file/UZw31KIZ#fz93YIBfs3ORzGyEYxCWVMPMY_xC5DDB-bZQy10KN3s

[tebasuna51]

Your sample is a DTS-ES with the phantom back channel matrixed in discrete surround channels, it is not a true (discrete) 7 channels.
Only a hardware player 6.1 extract the phantom BC to the BC speaker.
Many soft only inform/play it like 5.1
Read about DTS-ES here (https://en.wikipedia.org/wiki/DTS,_Inc.)

eac3to inform (with the -logdts parameter):
eac3to v3.52
command line: "C:\Portable\eac3to\eac3to.exe" "C:\Users\Pepe\Downloads\output.dts" "C:\Users\Pepe\Downloads\output.dts_.dts" -logdts -progressnumbers -log="C:\Portable\eac3to\UsEac3to\UsEac3To.log"
------------------------------------------------------------------------------
+ DTS-Core
- frameSize 2012
- DTS-ES +
- channelNo 5
- lfe 1
- channelDescr 5.1
- samplingRate 48000
- bitDepth 24
- bitrate 1509000
- samplesPerFrame 512
- copyHistory 1
DTS-ES, 5.1 channels, 0:01:00, 1509kbps, 48kHz, dialnorm: 0dB

A true (discrete) 7 channels DTS is this:
eac3to v3.52
command line: "C:\Portable\eac3to\eac3to.exe" "D:\Test\AudioD\Samples\dts\dts_chan\331.dts" "D:\Test\AudioD\Samples\dts\dts_chan\331.dts_.dts" -logdts -progressnumbers -log="C:\Portable\eac3to\UsEac3to\UsEac3To.log"
------------------------------------------------------------------------------
Running in fast mode
Removing dialnorm
+ DTS-Core
- frameSize 2013
- DTS-ES +
- channelNo 6
- lfe 1
- channelDescr 6.1
- samplingRate 48000
- bitDepth 16
- bitrate 1509750
- extAudio XCh
- samplesPerFrame 512
- copyHistory 1
DTS-ES, 6.1 channels, 0:00:20, 1510kbps, 48kHz, dialnorm: 0dB

MediaInfo differences:

Discrete 6.1 Matrixed 6.1
------------------ ------------------
Formato : DTS ES XCh DTS ES
Nombre comercial: DTS-ES Discrete DTS-ES
Canal(es) : 7 canales 7 canales
Channel layout : C L R Ls Rs Cb LFE C L R Ls Rs Cb LFE

[eXtremeDevil]

Sorry, I kind of lost myself with technical stuff... but I get it, it is not a true 6.1 audio. But, if connected in passthrough to a 6.1 capable home cinema or something like that, would it be recognized as such? Or as you say, extract the phantom BC to the BC speaker and therefore kind of "convert" or "output" as 6.1?

Thanks!

[tebasuna51]

Like I say a 6.1 home cinema (hardware player) can send the BC mixed in SL-SR to the BC speaker.

A 5.1 player create a phantom BC channel when is played in a 5.1 system.

You can decode that DTS-ES matrixed in 6 wav files, create a stereo (16 bits) with SL-SR and after extract the center part with the old CenterCut (http://www.moitah.net/download/latest/Center_Cut_GUI.zip) and recode now the 7 discrete channels to any codec compatible.

You can check in your 6.1 audio system the DTS-ES channels test attached (https://www.sendspace.com/file/9wozpq)(also a eac3 created from the matrixed one with the CenterCut procedure)

[eXtremeDevil]

Like I say a 6.1 home cinema (hardware player) can send the BC mixed in SL-SR to the BC speaker.

A 5.1 player create a phantom BC channel when is played in a 5.1 system.

You can decode that DTS-ES matrixed in 6 wav files, create a stereo (16 bits) with SL-SR and after extract the center part with the old CenterCut (http://www.moitah.net/download/latest/Center_Cut_GUI.zip) and recode now the 7 discrete channels to any codec compatible.

You can check in your 6.1 audio system the DTS-ES channels test attached (https://www.sendspace.com/file/9wozpq)(also a eac3 created from the matrixed one with the CenterCut procedure)

OK, I'll see what I end up doing, thank you very much.