Android Dolby Digital Passthrough only present in recordings
#1
Hi there,

I've recently setup my new environment:
  • TV Headend 4.3 (Debian) on a Helios 64
  • TV Card is an Octopus Net
  • Kodi 18 on a Nvidia Shield TV Pro 2019 connected via HDMI to …
  • AVR Marantz SR5015

The goal is to passthrough the sound stream to the AVR without any processing by Kodi. Everything works except LiveTV. In detail:
  • Netflix Android Native App: works (DD, Dolby Atmos)
  • Kodi playing movies with AC3, DTS: works
  • Kodi LiveTV playing AC3 (shown in Channel settings: Audio Track - 5.1/AC3) gives me: PCM Multi Channel In
  • Kodi LiveTV recording the same channel, stopping LiveTV and play the recording: Dolby Audio - DD + DSur
Between playing the LiveTV Channel (Multichannel PCM) and the recording of the LiveTV Channel (DD)  there's a noticeable difference in the sound. In MultiPCM the sound from the back and from the Subwoofer is existent but quite weak. Processing the sound directly from the AVR as AC3 sounds much better.

Passthrough in general works: Native Netflix, playing movies via Kodi, playing recordings from LiveTV give me the correct sound stream. Only LiveTV fails to passthrough the sound to the AVR. So I can definitely exclude as source of errors:
  • Android settings
  • Kodi: System settings -> Display + Audio (allow passthrough is set, number of channels: 5.1, output configuration: best match)
  • Kodi: Playback -> Videos
In TV -> Playback: Delay channel switch is set to 0 ms, Fallback Framerate is set to 50 Hz (PAL Europe). So there's not much to set.

To exclude also TVHeadend as the bad boy I re-activated my previous VDR installation and get the same problem there. LiveTV gives me PCM Multichannel instead of Dolby Digital.

On my previous environment (Linux HTPC with Kodi 16, AVR SR5005 connected by optical cable) the AVR received the DD signal. So basically LiveTV with DD passthrough has to work.

What did I miss? On which point the LiveTV DD stream is getting lost and being processed by Kodi to Multichannel PCM?
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#2
This is a normal behavior since Kodi 17. It is not a bug, it was a design decision by the Kodi devs. It’s the case for all pvr addons, at least for VDR and TVHeadend.

There is a workaround. Configure the „number of channels: 2.0“. This gives you audio passthrough and also works for 5.1 Dolby Digital.

What is wrong with (L)PCM (besides from not showing the Dolby logo at your avr)? Wink

After a little struggle, I am fine with it (PCM/LPCM) for some years now. Movies audio passthrough works as expected. It’s only the pvr live tv, recordings audio passthrough also works as expected.

Regards Hoppel
frontend: nvidia shield tv 2019 pro | apple tv 4k | sonos arc 5.1.2 | lg oled65c97la
backend: supermicro x11ssh-ctf | xeon | 64gb ecc | wd red | zfs raid-z2 | dd max s8

software: debian | proxmox | openmediavault | docker | kodi | emby | tvheadend | fhem | unifi
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#3
(2020-12-14, 00:43)hoppel118 Wrote: This is a normal behavior since Kodi 17. It is not a bug, it was a design decision by the Kodi devs.
Hmm, should I file a bug report?

(2020-12-14, 00:43)hoppel118 Wrote: There is a workaround. Configure the „number of channels: 2.0“. This gives you audio passthrough and also works for 5.1 Dolby Digital.
No, it doesn't. If I select 2.0 (best fit, optimized, fixed), I'll get 2.0. The AVR shows me then PCM 2.0 Stereo.

(2020-12-14, 00:43)hoppel118 Wrote: What is wrong with (L)PCM (besides from not showing the Dolby logo at your avr)? Wink
I compared a some minutes of a movie playing directly in LiveTV while recording with the recording.

DD will be processed by the AVR, PCM is sent by the Kodi device. In DD the rear speaker are fare more noticeable. The subwoofer seems also being more present. And the location of the sound spots is more distinct in DD than in PCM. I guess, the AVR is doing something more in the sound processing.
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#4
Hi,

this is the way to go for some years now. I googled and found the thread where it was discussed initially:

https://forum.kodi.tv/showthread.php?tid=284580

Read the complete thread and you will find the answers.

(2020-12-14, 22:06)musv Wrote: Hmm, should I file a bug report?

No, I don’t think that it will ever change again. It was a design decision:

https://forum.kodi.tv/showthread.php?tid...pid2385467

(2020-12-14, 22:06)musv Wrote: No, it doesn't. If I select 2.0 (best fit, optimized, fixed), I'll get 2.0. The AVR shows me then PCM 2.0 Stereo.

Sorry, I forgot that you also have to:

Quote:set your audio configuration to 2.0 channels, activate passthrough and(!) "enable Dolby Digital (AC3) transcoding“

https://forum.kodi.tv/showthread.php?tid...pid2490645

and maybe disable "Player -> Sync Playback to Display".

Quote:https://forum.kodi.tv/showthread.php?tid...pid2524307

I recommend to configure kodi according to your environment (no. of channels 5.1/7.1 for example) and accept pcm/lpcm.

Regards Hoppel
frontend: nvidia shield tv 2019 pro | apple tv 4k | sonos arc 5.1.2 | lg oled65c97la
backend: supermicro x11ssh-ctf | xeon | 64gb ecc | wd red | zfs raid-z2 | dd max s8

software: debian | proxmox | openmediavault | docker | kodi | emby | tvheadend | fhem | unifi
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#5
double post
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#6
(2020-12-15, 05:23)hoppel118 Wrote: Sorry, I forgot that you also have to:
Quote:set your audio configuration to 2.0 channels, activate passthrough and(!) "enable Dolby Digital (AC3) transcoding“
Thanks, got it. The Caveat was "Enable Dolby Digital (AC3) Transcoding". This option appears only, if Audio Configuration has been set to 2.0. So I overlooked this option, when I changed the configuration from 5.1 to 2.0.

What does "transcode" mean exactly here?
Source DD → Decoded to PCM → Re-encoded to DD → sent to AVR?
(2020-12-15, 05:23)hoppel118 Wrote: I recommend to configure kodi according to your environment (no. of channels 5.1/7.1 for example) and accept pcm/lpcm.
What I've written above is exactly the same written on the 3rd page of your link:
(2017-02-23, 13:20)noggin Wrote:
(2017-02-13, 02:58)nickr Wrote: There should be no difference in sound quality, although if the audio coming from your TV broadcaster is EAC3 (ie extended not plain ac3) then another thread tells me there might be problems.

Set speakers on 5.1 (in kodi) if you have 5.1 real speakers.

That's only the case if the AV Receiver is doing a straight 5.1 decode in the same way that Kodi is. If the AVR has processing (dynamic range reduction etc.) that is based on the Dolby metadata then the audio won't be the same in both use cases. With passthrough the AVR receive metadata, with Kodi PCM decode it won't.
How I wrote above: There's a noticeable difference between PCM Multichannel and DD.

I understand the problem of the asynchronous audio. But at least in the past years I had this problem only very few times after resuming by timeshift. And if I have the choice between better sound (DD) or exact synchronized sound in timeshift I choose the better sound quality.

And I've never had a native PCM Multichannel Input-stream in any media used in Kodi. So 2.0 is ok for me with PCM.
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#7
(2020-12-16, 18:17)musv Wrote: Thanks, got it. The Caveat was "Enable Dolby Digital (AC3) Transcoding". This option appears only, if Audio Configuration has been set to 2.0. So I overlooked this option, when I changed the configuration from 5.1 to 2.0.

What does "transcode" mean exactly here?
Source DD → Decoded to PCM → Re-encoded to DD → sent to AVR?

Yes - exactly that. Any multichannel audio - DD/AC3, DD+/E-AC3, DTS, AAC, FLAC, PCM etc.is decoded to PCM (unless it's PCM already) and is then re-encoded to Dolby Digital 5.1. I don't know if any metadata present in the source DD/DTS/AAC etc. is passed-through (with requisite conversion) or if the re-encode just uses a standard set of metadata (for things like DialNorm, LoRo vs LtRt, Line/RF compression etc.)
Quote:And I've never had a native PCM Multichannel Input-stream in any media used in Kodi. So 2.0 is ok for me with PCM.

I have a few early PCM Blu-rays - very early Blu-ray releases pre-dated both DTS HD MA and Dolby True HD lossless compression mastering tools AIUI. Multichannel FLAC and AAC (neither of which can be bitstreamed - at least in almost any set-up) will be re-encoded to Dolby Digital in this case (and in the case of FLAC you'll have introduced lossy compression to an otherwise lossless format). FYI AAC 5.1 is used in the UK for our DVB-T2 TV.
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#8
I am fine with PCM/LPCM for pvr live tv. Sorry, but a working timeshift is more relevant to me than Dolby Digital. Wink

Regards Hoppel
frontend: nvidia shield tv 2019 pro | apple tv 4k | sonos arc 5.1.2 | lg oled65c97la
backend: supermicro x11ssh-ctf | xeon | 64gb ecc | wd red | zfs raid-z2 | dd max s8

software: debian | proxmox | openmediavault | docker | kodi | emby | tvheadend | fhem | unifi
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#9
(2020-12-16, 20:10)noggin Wrote:
(2020-12-16, 18:17)musv Wrote: What does "transcode" mean exactly here?
Source DD → Decoded to PCM → Re-encoded to DD → sent to AVR?
Yes - exactly that.
That's of course not a good solution. But the results are still better than pure PCM Multichannel
(2020-12-16, 20:10)noggin Wrote: Any multichannel audio - DD/AC3, DD+/E-AC3, DTS, AAC, FLAC, PCM etc.is decoded to PCM (unless it's PCM already) and is then re-encoded to Dolby Digital 5.1.
That's not correct. I played a DTS movie, which is recognized by my AVR as DTS. Music files I haven't tested. But AFAIK also in the past any file type (MP3, Flac, Ogg, etc) has been decoded by Kodi (ffmpeg).

The question is now, if every DD signal will be double-recoded or only PVR Live-TV stuff. The latter would be acceptable to me. Maybe I'll have a look into the source code in the next days for more understanding. I'm not a C++-Cheek, but the Kodi code is quite easy to read.

But generally I like the idea more to send as much as possible unprocessed to the AVR.
(2020-12-16, 21:21)hoppel118 Wrote: I am fine with PCM/LPCM for pvr live tv. Sorry, but a working timeshift is more relevant to me than Dolby Digital. Wink
Of course everyone has a different opinion. If I used Kodi for example on an ordinary Desktop PC with Headphones or a cheap sound set then timeshift is much more important. In my case it's annoying, because the sound appears flat without any life. With PCM I can stop watching movies from TV and degrade PVR to news and talkshows. Alternatively I can record every movie and watch afterwards. As you can see the goals are different.

Probably the much better solution would have been a setting in PVR section:
  • Decode DD to PCM for accurate audio synchronisation in LiveTV
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#10
(2020-12-17, 12:37)musv Wrote: The question is now, if every DD signal will be double-recoded or only PVR Live-TV stuff. The latter would be acceptable to me.

No, not every DD signal will be transcoded! It’s only the pvr live tv stuff.

With movies (dvd, bluray, uhd) you still get Dolby Digital, Dolby Digital Plus, Dolby TrueHD and Dolby Atmos (Plus/TrueHD).

I have a Sonos 5.1.2 Soundsystem. LPCM sounds fine for my ears with this setup. Sonos doesn’t support DTS. So all the DTS audio formats are also PCM/LPCM.

(2020-12-17, 12:37)musv Wrote: Probably the much better solution would have been a setting in PVR section:
  • Decode DD to PCM for accurate audio synchronisation in LiveTV

Yes, that would have been a fantastic solution with max. flexibility for all of us. Now, it’s this way for some years (since Kodi 17), but maybe someone or you is interested in changing this behavior. Wink

Regards Hoppel
frontend: nvidia shield tv 2019 pro | apple tv 4k | sonos arc 5.1.2 | lg oled65c97la
backend: supermicro x11ssh-ctf | xeon | 64gb ecc | wd red | zfs raid-z2 | dd max s8

software: debian | proxmox | openmediavault | docker | kodi | emby | tvheadend | fhem | unifi
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#11
(2020-12-17, 12:37)musv Wrote:
(2020-12-16, 20:10)noggin Wrote: Any multichannel audio - DD/AC3, DD+/E-AC3, DTS, AAC, FLAC, PCM etc.is decoded to PCM (unless it's PCM already) and is then re-encoded to Dolby Digital 5.1.
That's not correct. I played a DTS movie, which is recognized by my AVR as DTS. Music files I haven't tested. But AFAIK also in the past any file type (MP3, Flac, Ogg, etc) has been decoded by Kodi (ffmpeg).

That would happen if you enabled DTS passthrough obviously - but if you didn't (say because your TV/AVR is DD only) then DTS is decoded to PCM and re-encoded to DD like all other non-DD multichannel stuff.
Quote:The question is now, if every DD signal will be double-recoded or only PVR Live-TV stuff. The latter would be acceptable to me. Maybe I'll have a look into the source code in the next days for more understanding. I'm not a C++-Cheek, but the Kodi code is quite easy to read.

Files with DD are replayed as encoded - no decode and re-encode (i.e. no transcode). Only PVR stuff is decoded and re-encoded.
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#12
As it is not really a bug, I created a feature request:
https://forum.kodi.tv/showthread.php?tid=359194

Maybe FernetMenta or who's currently working on the PVR section is open for this advice. And for now the workaround is ok for me.
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#13
(2020-12-17, 18:46)musv Wrote: As it is not really a bug, I created a feature request:
https://forum.kodi.tv/showthread.php?tid=359194

Maybe FernetMenta or who's currently working on the PVR section is open for this advice. And for now the workaround is ok for me.

Have replied - the AC3 Transcode option isn't just for PVR users - it's there for anyone who has a DD only system and who wants to listen to other multichannel audio (PCM, FLAC, AAC, DTS etc.)

This issue was discusses A LOT when the behaviour in Live TV was changed quite a few years ago, whilst I know lots of people would like it to return, there was no sign that the developers were minded to do so.
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