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HDMI and surround sound - what's going on?


Standard Member
I thought HDMI is supposed to be able to deliver picture as well as sound?

How come I need to buy an optical cable for my Xbox 360 and WD Live TV for surround sound even though both devices can connect with HDMI leads?


Prominent Member
Might help people to help you if you told us a bit more about what you are trying to connect the XBox/WD to ...

Joe Fernand

Distinguished Member
AVForums Sponsor
HDMI can and will deliver sound and vision though it requires that the Source is outputting sound and vision the Sync (AV Amp, Display, Projector) can decode.

Within the HDMI signal bus the Source and Sync will usually automatically choose what to output - you sometimes have the option to overrule the Auto selection, sometimes not!

If your Sync (Display or Projector) doesn't handle audio you may well have a Source that's only outputting Video via HDMI so you cant decode audio on an intermediate device (AV Amp).

If your Source outputs the 'wrong' audio you may again get no audio at the Sync - if your Source is set to output 5.1 over HDMI and its connected to a Stereo only Display you wont get audio on the Display.

Some devices will support video + audio over HDMI + simultaneous Analogue of Digital audio via RCA or Optical - others wont and you can only have one audio stream at any time.

Within the HDMI signal bus the audio track is encoded into the video stream so any device that's seeing an image has the potential to decode the audio if audio is available within the HDMI signal.

As Mark says a bit more info on what is connected to where and how you have the User settings configured.



Established Member
Oh, and make sure your Xbox is set to output via HDMI! :)


Prominent Member
From the looks of things, your 'amp' does not decode sound from HDMI, that is why you need to use the optical connection as well.

Some lower end (or older) devices just act as an HDMI switch allowing two sources to be attached to one ionput on the display but they do not process the sound passing over the HMDI cable.


Established Member
You learn something new every day!! Mind you, devices like this will become less and less common I guess...

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