2.1 Downmixing from Surround: How does it work?

[BullBuchanan]

I've recently "downgraded" to a 2.1 setup and due to a lightning strike have a currently limited setup. I have my new receiver (denon x3700h) setup to reflect my 2.1 setup, and I'm only streaming content from my older television right now while I wait for the new one. When I play content on it,my receiver displays "stereo" and that got me thinking

Where is the stereo mode determined if content is available in 5.1/7.1. Does the television know that the receiver it's connected to only has a 2 channel configuration or if it has say a Dolby Atmos stream is it sending that and then my receiver is doing the downmix to stereo on my behalf given my settings?

I found the following info from searching here, but I'm pretty sure it's how the final audio streams are generated during the master and I'm a bit unclear as to what happens in the wild. https://professionalsupport.dolby.c...d-Stereo-downmix-settings-work?language=en_US

I know on my BluRay player I could select an audio format from the menu, but my TV doesn't have that option and I'd still like to understand more detail about how a receiver handles a surround format file in a 2.1. IS there an embedded stereo file within that drops the LFE, does it downmix everything in real time adding the missing channel data into my existing channels, or does it just drop the channel info for channels I don't have?

 

[Chrispy]

If the Denon switched to stereo mode automatically I'd suspect that's the signal your tv is outputting (i.e. 2.0). With bass management in your Denon you can have the stereo play as 2.1 essentially with your 2 speakers/sub. Many older tvs only provided 2.0 output. What model tv is it? Are the streaming apps built into your tv capable of multich and you have the app set to play such vs the 2.0 version (not much 7.1 streaming out there)?

 

[BullBuchanan]

If the Denon switched to stereo mode automatically I'd suspect that's the signal your tv is outputting (i.e. 2.0). With bass management in your Denon you can have the stereo play as 2.1 essentially with your 2 speakers/sub. Many older tvs only provided 2.0 output. What model tv is it? Are the streaming apps built into your tv capable of multich and you have the app set to play such vs the 2.0 version (not much 7.1 streaming out there)?

I have the sub setup to crossover and have it in whatever Denon's version of Plus mode is so that it plays in addition to the speakers - as my measurements indicates this achieves the flatest bass response (at least when i recalibrate for the new setup), but I'm guessing it's not actually getting the LFE channel data which is a separate track.

The tv is an old Samsung 55 H6350 and it has an output option for PCM, Dolby, DTS and DTS Neo, so I'm sure I could manipulate it with the settings somehow, but that's not really my point. I'm replacing the TV, so I'm not really trying to fix anything exactly.

I'm just trying to understand the chain of events that happen from the source to the speakers with respect to multichannel formats so that i can make educated decisions moving forward.

 

[Chrispy]

I was more thinking of what was happening with your current tv....what do you have set for output?

In looking around briefly I spot this paragraph in one blog :
"Since the early days of Dolby Digital in the 90s, Dolby-certified multichannel audio soundtracks have been designed to ensure compatibility with systems composed of less than 5 speakers. All Dolby 5.1 soundtracks (Digital, Digital Plus, True HD) contain additional metadata which may be used by the decoder to distribute sounds intended for absent channels between the available speakers. All TVs, 4K Blu-ray players and AV receivers use this metadata to downmix 5.1 soundtracks."

More technical info I see here https://www.audiokinetic.com/library/edge/?source=Help&id=downmix_tables

I'd also like to know more about downmixing, even though I don't utilize it currently....I'd rather have the additional speakers

 

[BullBuchanan]

I was more thinking of what was happening with your current tv....what do you have set for output?

In looking around briefly I spot this paragraph in one blog :
"Since the early days of Dolby Digital in the 90s, Dolby-certified multichannel audio soundtracks have been designed to ensure compatibility with systems composed of less than 5 speakers. All Dolby 5.1 soundtracks (Digital, Digital Plus, True HD) contain additional metadata which may be used by the decoder to distribute sounds intended for absent channels between the available speakers. All TVs, 4K Blu-ray players and AV receivers use this metadata to downmix 5.1 soundtracks."

More technical info I see here https://www.audiokinetic.com/library/edge/?source=Help&id=downmix_tables

I'd also like to know more about downmixing, even though I don't utilize it currently....I'd rather have the additional speakers

I have PCM set for output. There's no bitstream option so it would seem my TV is going whatever decoding is necessary. The manual claims it can support Dolby + files played locally, but Netflix uses Dolby+ and the receiver just says stereo. The TV also has a regular Dolby Digital output as well as DTS, but I'm not really sure what's actually happening with those. Is the TV throwing whatever audio it gets into a Dolby wrapper and sending it to the receiver, or does it only do that if it gets it?

Either way, this part of the chain will only exist for another 2 days until my U8G gets here.