stdP
One Swiss dinosaur in Polly Gosling's anorak hood
It's the sort of thing that I would imagine would vary depending on who made the display adapter and what model it is. Laptops having the ability makes sense, but I don't know if the HDMI output for a typical GPU carries sound, for example.
I think pretty much every system I've seen with HDMI has supported audio out (although I've only used AMD and Intel kit myself). Assuming you're using windows the HDMI output devices should be visible in the sound devices list, in linux aplay and arecord will show them up; from my laptop:
Code:
stdp@laptop:~# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC3235 Analog [ALC3235 Analog]
Subdevices: 0/1
Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 3: HDMI 0 [HDMI 0]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 7: HDMI 1 [HDMI 1]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 8: HDMI 2 [HDMI 2]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 9: HDMI 3 [HDMI 3]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 10: HDMI 4 [HDMI 4]
Subdevices: 1/1
Subdevice #0: subdevice #0
stdp@laptop:~# arecord -l
**** List of CAPTURE Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC3235 Analog [ALC3235 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 2: ALC3235 Alt Analog [ALC3235 Alt Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
No real reason not to use analogue audio if it works for you, but for home cinema setups using a receiver being able to use a single device and cable for audio and video is advantageous. Just wish receivers and TVs existed with DisplayPort though :'(
Swerving back in the general direction of the topic, as mentioned above ublock does a fair job of blocking youtube adverts, but I usually go one step further and use a tool called youtube-dl to pull down videos to an MKV file rather than viewing them through youtube; any app built in to a TV or set-top box won't allow you any degree of blocking ads or tracking scripts.