[mrfeh]

My setup: hdhomerun->tvheadend server and client->kodi->amplifier (via hdmi)->tv.  All the software (tvheadend/kodi) is running on a RPi 4, Raspbian Buster. Kodi version is 18.7.

I have things configured to pass through audio to the amp for decoding there. I noticed that the audio level of the same program is quite different between the live stream and watching the recording of the live stream. The recording audio level is much lower.

Known problem? Configuration need to be tweaked?

Thanks!

[noggin]

When you watch Live TV regular Kodi builds will always decode any AC3/Dolby Digital to multichannel PCM (and then mix-down to stereo if you have 2.0 configured for output and the source is 5.1) There is no option in Kodi to passthrough/bitstream when watching Live TV, so your Amp won't be decoding AC3, Kodi will. (Kodi removed the ability to bitstream/passthrough Live TV audio a while back because of issues coping with bitstream errors and sync ISTR)

When you watch Recorded TV Kodi will be able to passthrough AC3/Dolby Digital to your amp and then your amp will decode to multichannel PCM.

The level difference is likely to be because of a difference in how Kodi and your AVR are decoding AC3 audio to PCM?  What happens if you disable passthrough and let Kodi decode at all times, rather than your Amp decode recordings and Kodi decode live?

(One other issue worth checking is that in some countries there is more than one audio stream broadcast - sometimes there are both stereo MP2/AAC and 5.1 Dolby Digital/AC3 - if you are playing different ones in different modes - you may also hear a level difference. In the UK our satellite broadcasts carry AC3 for the main show audio, but a secondary MP2 stereo stream carrying Audio Description some of the time for instance.)

[mrfeh]

When you watch Live TV regular Kodi builds will always decode any AC3/Dolby Digital to multichannel PCM (and then mix-down to stereo if you have 2.0 configured for output and the source is 5.1) There is no option in Kodi to passthrough/bitstream when watching Live TV, so your Amp won't be decoding AC3, Kodi will. (Kodi removed the ability to bitstream/passthrough Live TV audio a while back because of issues coping with bitstream errors and sync ISTR)

This was my experience, until I did a fair amount of digging and discovered that with certain settings (one of them being that you say you have 2 speakers when in fact I have 5.1), it is possible to have kodi pass through encoded audio for live TV.  My amp says it is receiving Dolby.

[noggin]

When you watch Live TV regular Kodi builds will always decode any AC3/Dolby Digital to multichannel PCM (and then mix-down to stereo if you have 2.0 configured for output and the source is 5.1) There is no option in Kodi to passthrough/bitstream when watching Live TV, so your Amp won't be decoding AC3, Kodi will. (Kodi removed the ability to bitstream/passthrough Live TV audio a while back because of issues coping with bitstream errors and sync ISTR)

This was my experience, until I did a fair amount of digging and discovered that with certain settings (one of them being that you say you have 2 speakers when in fact I have 5.1), it is possible to have kodi pass through encoded audio for live TV.  My amp says it is receiving Dolby.

Are you sure you don't mean Transcode to 5.1 AC3/Dolby Digital (that's appears in the passthrough options settings when you select 2.0 speakers as a config)?  

That's not passthrough (even though it's in the passthrough settings) - that's decode and then re-encode i.e. the Dolby Digital to PCM 5.1 Kodi decode still happens, but instead of this audio being output as PCM 5.1, it's re-encoded to AC3/Dolby Digital (that's what the 2.0 vs 5.1 channel setting triggers - as you've told Kodi you can't output PCM 5.1 - so it offers an option to re-encode to Dolby Digital AC3)

This transcode (decode + recode = transcode) may not preserve the Dolby Digital metadata (which carries information like dialogue normalisation settings, RF vs Line compression settings, LoRo vs LtRt mix down, gains for mix-downs etc.) from the source AC3 that will impact how your AVR then handles the decoding of the transcoded/re-encoded audio, which could also mean a level difference (as could other issues in the transcode chain). Your AVR will say it is receiving Dolby in this scenario - but that isn't the same as passthrough - nor does it confirm that you're AVR is receiving the broadcast AC3 bitstream untouched.

[mrfeh]

When you watch Live TV regular Kodi builds will always decode any AC3/Dolby Digital to multichannel PCM (and then mix-down to stereo if you have 2.0 configured for output and the source is 5.1) There is no option in Kodi to passthrough/bitstream when watching Live TV, so your Amp won't be decoding AC3, Kodi will. (Kodi removed the ability to bitstream/passthrough Live TV audio a while back because of issues coping with bitstream errors and sync ISTR)

This was my experience, until I did a fair amount of digging and discovered that with certain settings (one of them being that you say you have 2 speakers when in fact I have 5.1), it is possible to have kodi pass through encoded audio for live TV.  My amp says it is receiving Dolby.

Are you sure you don't mean Transcode to 5.1 AC3/Dolby Digital (that's appears in the passthrough options settings when you select 2.0 speakers as a config)?  

That's not passthrough (even though it's in the passthrough settings) - that's decode and then re-encode i.e. the Dolby Digital to PCM 5.1 Kodi decode still happens, but instead of this audio being output as PCM 5.1, it's re-encoded to AC3/Dolby Digital (that's what the 2.0 vs 5.1 channel setting triggers - as you've told Kodi you can't output PCM 5.1 - so it offers an option to re-encode to Dolby Digital AC3)

This transcode (decode + recode = transcode) may not preserve the Dolby Digital metadata (which carries information like dialogue normalisation settings, RF vs Line compression settings, LoRo vs LtRt mix down, gains for mix-downs etc.) from the source AC3 that will impact how your AVR then handles the decoding of the transcoded/re-encoded audio, which could also mean a level difference (as could other issues in the transcode chain). Your AVR will say it is receiving Dolby in this scenario - but that isn't the same as passthrough - nor does it confirm that you're AVR is receiving the broadcast AC3 bitstream untouched.

Ah, very interesting. Thanks for the explanation.

I guess I'll live with PCM for live TV. If I want audio passed through, I'll have to watch things as a recording.