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View Full Version : HDMI/Dolby Digital/Optical question




richlyon
Feb 24, 2008, 04:38 PM
Hi - a question about HDMI and Dolby Digital. Ive managed to get Apple TV to route hi def to the TV (Sony Bravia) via HDMI and Dolby Digital to the decoder via optical. My TV has optical passthrough and output, so Ive tried connecting the TV to the decoder (i.e. Apple TV -> (HDMI) -> TV -> (Optical) -> Decoder). I can hear stereo, but the decoder no longer detects Dolby Digital content.

Question: What do you think is breaking? Is Apple TV not passing 5.1 up the HDMI cable, do you need a special HDMI cable, can HDMI pass 5.1, is the TV not passing it?

Im trying to save a cable and having to manually switch inputs on the decoder when I switch between TV and Apple TV, so all thoughts appreciated.



Peace
Feb 24, 2008, 04:42 PM
Whats breaking it is HDCP. You can pass through 5.1 Dolby ac-3 via HDMI but not twice. It's all part of the HDMI digital rights management.

Best way to get the 5.1 is by sending the HDMI video signal through the HDMI>Apple TV and the 5.1 audio to an amplifier that has optical digital input.

Avatar74
Feb 24, 2008, 04:53 PM
Hi - a question about HDMI and Dolby Digital. Ive managed to get Apple TV to route hi def to the TV (Sony Bravia) via HDMI and Dolby Digital to the decoder via optical. My TV has optical passthrough and output, so Ive tried connecting the TV to the decoder (i.e. Apple TV -> (HDMI) -> TV -> (Optical) -> Decoder). I can hear stereo, but the decoder no longer detects Dolby Digital content.

Question: What do you think is breaking? Is Apple TV not passing 5.1 up the HDMI cable, do you need a special HDMI cable, can HDMI pass 5.1, is the TV not passing it?

Im trying to save a cable and having to manually switch inputs on the decoder when I switch between TV and Apple TV, so all thoughts appreciated.

I think this is a function of HDCP, which was developed originally for DAT. HDCP prevents daisy chain pass through of digital audio to prevent copying. Frankly, I've never actually seen pass through work. I can't get my TV to pass HDMI audio from my DVD player over it's optical output to the receiver. Only the TV tuner's audio will pass. This may have differed in previous AppleTV software but the benefits of AppleTV far outweigh the detriments of implemented HDCP.

I have all my optical audio sources connected directly to my receiver, so HDCP has never been a problem.

Avatar74
Feb 24, 2008, 04:53 PM
oops duplicate post. deleted.

richlyon
Feb 24, 2008, 05:03 PM
Thanks guys. I did a bit of googling (maybe should have done some more before posting!) and it looks like the TV may (also) be suspect e.g. DTV Forum (http://www.dtvforum.info/index.php?showtopic=55628&st=660&p=904210&#entry904210) - Looks like most TVs dont pass DD5.1 (although apparently there are firmware updates that can enable it). Oh well - two key presses instead of one. Life could be harder, I suppose. Thanks!

johnboiles
Jan 23, 2010, 12:17 PM
This makes me very frustrated with hdcp. It's another case of crippling technology in the name of drm. There are better ways to rip blu-ray and hd content; seriously why downsample my optical out?

It feels like a step backwards. Anyone know if VESA DisplayPort does the same thing? I hear the newest spec is way more technically impressive than HDMI. Maybe Apple had it right all along -- if they'd just add audio to it that is.