[gregeeh]

Hi all,

Odroid N2 with CE 19.3, TvH Server 4.3-2064~gabcb0ea67 on NAS.

I have an HDHR and I’m using it with TVH using IPTV and it’s been great. Recently the audio level has gone very low, like really low, for SD TV Channels.  HD Channels have remained the same.

Using the HDHR URL's for SD & HD Channels in either VLC or the W11 HDHR Client shows the audio levels to be the same.

So why have they changed in kodi?

TIA

[noggin]

Hi all,

Odroid N2 with CE 19.3, TvH Server 4.3-2064~gabcb0ea67 on NAS.

I have an HDHR and I’m using it with TVH using IPTV and it’s been great. Recently the audio level has gone very low, like really low, for SD TV Channels.  HD Channels have remained the same.

Using the HDHR URL's for SD & HD Channels in either VLC or the W11 HDHR Client shows the audio levels to be the same.

So why have they changed in kodi?

TIA

Where in the world are you watching TV ? HD Homeruns are sold in ATSC 1.0 and 3.0 versions, as well as DVB-T/T2 and DVB-C variants, and different countries use different audio formats.

Kodi doesn't support bitstream/passthrough in Live TV mode - so the audio is always decoded to PCM (or transcoded to DD 5.1 within Kodi if you have that option enabled) and how that is handled can vary between codecs.

For instance - in the UK we use MP2 for SD DVB-T and DVB-S audio, but AAC2.0/5.1 for HD DVB-T2 and AC3 2.0/5.1 for HD DVB-S2.  
(Also audio description is very different between DVB-T/T2 and S/S2 - with T/T2 supporting mono MP2/AAC narration streams that receivers mix with the MP2/AAC programme audio, whilst D/S2 has a second MP2 (for both HD and SD) that is pre-mixed by the broadcaster)

[gregeeh]

I live in Australia and thank you for your reply.  I will check out my passthrough options and see if that is causing the issue.  Thank you.

[noggin]

I live in Australia and thank you for your reply.  I will check out my passthrough options and see if that is causing the issue.  Thank you.

https://www.digitalbitrate.com/dtv.php?m...36&lang=en is useful

Looking at Perth 

ABC is all MP2 audio (aka 'mpg') for both SD and HD - with what looks like HE-AAC possibly for audio description?
7 is a mix of MP2, AC3 (aka Dolby Digital) and AAC. MP2 for 7's SD channels, AC3 for 7HD/7mateHD and AAC for the other HD services.
9 is a mix of MP2 for SD and AC3 for HD.
10 is a mix of MP2 for SD and AC3 for HD.
SBS is like ABC - MP2 audio for both SD and HD - with HE-AAC possible for audio description.

This looks like all SD services are MP2 audio, with HD services either MP2 (probably stereo only - though Ten seems to change MP2 bitrate on SD which may imply a 2.0/5.1 switch) - which appears to be the choice of PSBs ABC and SBS, AC3 (Dolby Digital capable of 2.0/5.1 switching - though all the AC3 seems to be fixed bitrate 384k so either the format change doesn't also include a bitrate change - or they run fixed 5.1?) for the main commercial HD services (7, 9 and 10) and AAC (possibly stereo only and lower bitrate) for the less popular HD subchannels on 7?

You will often hear level differences between MP2 and AC3 audio services carrying the same content (Kodi decodes all live TV audio to PCM - and then optionally re-encodes to 5.1)...

[gregeeh]

@noggin Thanks for your reply and looking into this for me.  I live in Sydney, not Perth, but the channels will be very similar if not the same.

What I noticed was all the SD Channels, MP2, had much lower volume than the HD Channels.  And yes I realise there will be a difference in volume between the different audio formats but the difference was such that we could not hear the MP2 and had to turn the volume to near full to be heard.

With further investigation I found the volume of the Odroid N2 was set low and increasing it to full fixed the problem.  Now both SD and HD Channels were the same.

This suggests I have some passthrough disabled?  My understanding is if not passthrough the Kodi volume is applied, if passthrough the Kodi volume is not applied.  However my passthrough settings look fine to me.

Thoughts?

TIA

[noggin]

Your settings explain it.  You have transcoding to Dolby Digital enabled. This means that 5.1 Live TV audio (probably on the AC3 HD channels - 7/9/10 but not ABC/SBS) will be re-encoded to 5.1 Dolby Digital AC3 rather than 5.1 (and probably the volume control setting in Kodi will be ignored).  The stereo MP2 stuff will be decoded to PCM 2.0 and subject to the volume control (the transcoding option is only used for multichannel, not stereo, audio)

If you disabled the Transcode to Dolby Digital you'd have the same volume on all channels I expect (or if you turned up the volume as you did to bring the MP2-decoded-to-PCM and AC3-transcoded-to-AC3 to match).

If you don't have a 5.1 audio system then re-encoding to Dolby Digital 5.1 isn't that great an idea.  If you DO have a 5.1 system - then it might be an idea to set your Number of Channels to 5.1 so that FLAC/AAC and other non-bitstreamed audio can be output in PCM 5.1 rather than lossy-transcoded to Dolby Digital? This will remove the option for transcoding to DD/AC3 but decoding to PCM is lossless and probably a better approach than an AC3 decode/re-encode.

[gregeeh]

@noggin Thank you once again for your reply.

I have set the Channels to 5.1, which removed the DD Transcoding Option, and the volume is now much better.  As I have a 5.1 audio system is this the best away to go to get the best audio experience?

Thanks again.

[noggin]

@noggin Thank you once again for your reply.

I have set the Channels to 5.1, which removed the DD Transcoding Option, and the volume is now much better.  As I have a 5.1 audio system is this the best away to go to get the best audio experience?

Thanks again.

If your 5.1 system is HDMI connected and capable of 5.1/7.1 PCM (pretty much every HDMI AVR since the very early ones have been) - then yes.  

The only reason for the Dolby Digital Transcoding option is for people with legacy SPDIF/Toslink amps that can't accept 5.1/7.1 PCM and have to have all 5.1 content in either DD or DTS lossy formats.  

Standard SPDIF/Toslink can only carry 2.0 PCM or DD/DTS lossy 2.0-5.1 (there are some DD and DTS variants that may allow for 6.1/7.1) hence the DD/AC3 transcode option is only offered when channels 2.0 is selected (sometimes people think channels = speakers - but it's better thought of as a definition of the number of PCM channels your system can cope with)

[gregeeh]

Thank you, yet again and much appreciated.

[gregeeh]

@noggin - As mentioned previously I just changed the Channels to 5.1 and all the TV Channels are now great.  Went to play an AAC Movie tonight and the sound was rubbish.  I've connected the eARC from my Sony X90J TV to my Sonos Bean Gen 2 Soundbar.  Changing the number of channels back to 2.0 fixes the audio.  Can you explain why?

Have a Merry Christmas and TIA

[noggin]

@noggin - As mentioned previously I just changed the Channels to 5.1 and all the TV Channels are now great.  Went to play an AAC Movie tonight and the sound was rubbish.  I've connected the eARC from my Sony X90J TV to my Sonos Bean Gen 2 Soundbar.  Changing the number of channels back to 2.0 fixes the audio.  Can you explain why?

Have a Merry Christmas and TIA

What does 'rubbish' mean?  

Was the movie with AAC sound 2.0 or 5.1?  

When you went back to 2.0 from 5.1 channels config did you still have Dolby Digital Transcoding enabled in the passthrough section?

I'm trying to work out if the issue you have is a difference between how your sound bar copes with 5.1 PCM (decoded from AAC with no quality drop) and 5.1 Dolby Digital (Transcoded from AAC - with a potential small quality drop), or whether you are seeing a difference between how your sound bar copes with 5.1 AAC mixed down to 2.0 PCM (i.e. stereo) in Kodi vs how it copes with 5.1 PCM from Kodi played in 5.1 by your sound bar.

You say you have a Sonos Beam Gen 2 - do you have the One SL rear/side surround speakers for your Sonos set-up to give you real 5.1 - or are you relying on the Sonos to do virtual 5.1 with a heck of a lot of psycho-acoustic DSP and room mapping and the side firing speakers?  The Beam first gen was a 3.0 speaker set-up that didn't really try to do any surround/height stuff AIUI - the gen 2 has added some heavy DSP processing to generate a fake surround/atmos sound field - but it's a bit variable.

What happens if you disable all passthrough and leave Channels 2.0 as your setting and listen to everything in stereo?

[gregeeh]

What does 'rubbish' mean?  

Sorry, my bad.  The sound was very low, muffled and you could not understand anything that was said.

Was the movie with AAC sound 2.0 or 5.1?  

Sound wias 5.1.

When you went back to 2.0 from 5.1 channels config did you still have Dolby Digital Transcoding enabled in the passthrough section?

Yes transcoding was enabled.

You say you have a Sonos Beam Gen 2

Yes, with One SL rear speakers.

What happens if you disable all passthrough and leave Channels 2.0 as your setting and listen to everything in stereo?

Everything works but sound is of course stereo.

I have been doing a lot of reading and searching to try and learn more about the different audio formats and I think I have discovered why the AAC movie sound was corrupted.  The issue with the movies sound only happens with AAC Movies and I had to select 2 Channels to hear the sound correctly.

Several comments I read suggest that AAC is not a supported eARC/ARC codec and hence why it needs transcoding in my instance.  Their exact comments of one are:

It isn't that your amp doesn't support AAC, it's that AAC is a codec that cannot be passthrough over any of HDMI, ARC, or spdif/toslink, it isn't part of the supported codec list. AAC never reaches/touches your amp.  If a codec cannot be passthroughed then it has to be decoded in the client device into uncompressed PCM.

Thanks once again for your input.

[noggin]

I have been doing a lot of reading and searching to try and learn more about the different audio formats and I think I have discovered why the AAC movie sound was corrupted.  The issue with the movies sound only happens with AAC Movies and I had to select 2 Channels to hear the sound correctly.

Several comments I read suggest that AAC is not a supported eARC/ARC codec and hence why it needs transcoding in my instance.  Their exact comments of one are:

It isn't that your amp doesn't support AAC, it's that AAC is a codec that cannot be passthrough over any of HDMI, ARC, or spdif/toslink, it isn't part of the supported codec list. AAC never reaches/touches your amp.  If a codec cannot be passthroughed then it has to be decoded in the client device into uncompressed PCM.

Thanks once again for your input.

It's true that AAC bitstreaming/passthrough over eARC/ARC/HDMI in general isn't widely supported (it's pretty/vanishingly rare).  

However this in't really relevant to your use case as with transcoding disabled and channels configured to 5.1 Kodi is outputting the AAC 5.1 audio from the movie file not as bitstreamed AAC but as 5.1 multichannel PCM that has been decoded from the AAC audio.

Kodi is doing, as the client device, precisely what your quote states client devices should do with 5.1 AAC :

If a codec cannot be passthroughed then it has to be decoded in the client device into uncompressed PCM.

As you aren't trying to bitstream/passthrough 5.1 AAC over eARC/HDMI you aren't hitting an AAC incompatibility. (In old versions of Kodi there was an AAC Passthrough option offered for bitstreaming/passthrough of AAC audio - but because support for AAC bitstreaming was so rare it was largely untested and removed a long time ago. (You now only get AC3/DD, E-AC3/DD+, DTS, Dolby True HD and DTS HD as options for passthrough, along with transcode to 5.1 AC3/DD)

Does Kodi + your Sonos system do the same muffled audio thing with all 5.1 AAC movies output as PCM (i.e. channels set to 5.1 and no transcoding) - or just one particular one?

If you configure channels to be 5.1 and disable all passthrough/bitstream of codecs - so everything is decoded to 5.1 - do other 5.1 AC3/DD, E-AC3/DD+, DTS, True HD, DTS HD 5.1/7.1 movies sound odd?

I have a regular Kodi set-up with a Denon AVR and a 5.0 speaker system (no sub woofer) and as the UK DVB-T2 HD platform uses 5.1 AAC for multichannel audio, I listen to a some 5.1 recorded TV audio via this route via various Kodi playback solutions, and it's always decoded to 5.1 PCM. I don't hear the issues you are hearing.  I'll set-up an N2 with CoreElec (it's not my daily driver at the moment) - and see if I get similar issues with 5.1 audio (though I'm not using eARC - I route my Kodi playback directly via the AVR along with my UHD BD player, my PS2, PS5, Apple TV4K and Sky Q)