Does Inspiron 15-7569 supports 5.1 surround sound output over HDMI?

I have a DELL laptop, model is Inspiron 15-7569. I have updated all drivers (BIOS, Intel Graphics 520 driver, Realtek driver, etc) using the tool "DELL update", which is shipped with the laptop.

My Speaker is Vizio SB4051-C0. I used "speaker test" function on its remote, and I can hear all 5 speakers and the subwoofer working correctly.

But when I connected the laptop and vizio speaker via HDMI cable, and then played a youtube video called "5.1 Dolby Surround Test", I found that the two rear speakers and subwoffer not working. Does this mean my laptop does not support 5.1 channel over HDMI? If yes, then can I buy an external USB audio interface? I found a cheap one in ebay called "Behringer UCA202 Audio Interface". It has optical output but no HDMI output. Although my vizio speaker supports optical input, the user manual states that HDMI has better voice quality than optical.

Thanks a lot for help!

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