How did this device activate 5.1 passthrough on my tv?

[Jacopo_4]

I have a Lenovo laptop without an optical audio output which I use as a media player connected to a TV via HDMI; the TV is connected to a Sony Home Theater 5.1 (BDV-E3100) via ARC.

As with many tvs, my JVC LE42-C550 is seen by windows as only capable of receiving stereo audio, so I was looking for a way to play 5.1 sound from the pc.

I decided to buy this http/www.ebay.co.uk/itm/HDMI-Audio-Extractor-Splitter-to-SPDIF-Optical-RCA-Stereo-L-R-Analog-Converter/250970565434?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 and an optical cable, hoping that I could then connect it to my home theatre system.

When I first connected the splitter box to the laptop I was expecting to be able to select 5.1 from this menu https/www.sevenforums.com/attachments/sound-audio/348693d1486632562t-my-asus-laptop-i-have-only-stereo-option-untitled.jpg
At the beginning I was a bit deluded by the fact that I could still see only stereo, but then I clicked on properties/supported formats and I saw

Max Number of Channels: 2

Encoded formats
- DTS Audio
- Dolby Digital

So I remembered reading somewhere that DTS and DD are audio formats that can carry signal for 6 speakers on 2 channels, so 2 channels doesn't necessarily means 2 speakers only

I tried with a couple of 5.1 short videos on kodi after enabling audio passthrough and both AC3 and DTS and it worked!

The splitter is sending the video signal to the tv via HDMI and audio to the home theatre via optical cable as expected, right?

No! I accidentally disconnected the optical cable and the audio was still playing (in 5.1), so it must be going through the HDMI cable connected to the tv's ARC port.
This is even better then expected because I can still use HDMI-CEC and have the home theater turn on and off with the tv.
And I didn't leave Dolby Pro Logic or DTS Neo:6 on, I was listening to real 5.1


If the HDMI splitter box isn't separating the audio from the video, what is it doing then? It's just sitting between the laptop and the tv....
I tried removing it and connecting the laptop to the tv directly and, no 5.1 anymore.

I'm very satisfied (apart from now having an optical cable I don't need), but I would like someone more expert to explain why it is working this way?

 

[getochkn]

Right from the details of the ebay listing.

HDMI output is identical to the HDMI input, run through.

So it's not stripping the audio, just copying it and passing it through still.

 

[Jacopo_4]

Right from the details of the ebay listing.

HDMI output is identical to the HDMI input, run through.

So it's not stripping the audio, just copying it and passing it through still.

That would mean that I could take it off the line and all would be the same, but if I do so I lose 5.1 audio. So something must be doing, not only copying and passing it through.

By the way, it has a switch with 3 positions (PASS-2CH-5.1CH); it's always set on 5.1 CH

 

[americanaudiophile]

The switch on the audio extractor may be changing the EDID of the TV so the laptop thinks that the TV can do 5.1 and so it sends 5.1 to the TV which passes it through the ARC..
Try another switch position to see what the effect is.

 

[Jacopo_4]

It only works in that position, in the other two I only get stereo

Would this mean the tv not being able to passthrough 5.1 is a licensing limitation rather than a hardware one?