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Old 21st September 2009, 07:52 PM   #1
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Default HDMI DAC - HDCP, licences...?

OK, I know this has been dealt with before. But HDMI is a wider-spread technology now and HDMI kit is cheaper.
- HDMI's bandwidth exceeds SPDIF, allows 8 channel 24/96 PCM. Yaldi.

but

- HDCP cleverly encodes everything for DRM.

OK. My questions are (for audio only):
Do you need to own a licence for the content to prevent HDCP working?
And/Or do you need to own a licence for HDCP decoding?
I have seen mentions of "membership" in order to build HDMI kit. Is this the case?
If content is unlicensed, is HDCP still a problem, or does it then become like any other digital interconnect?
Can HDCP be physically hacked and is this illegal if you own content licences?

And if HDCP is prohibitively expensive to develop, surely my best bet is to get a cheap HDMI receiver, gut it of everything except the HDMI processing and build a high quality DAC off the end of that? And then sell kits for billions to greedy DIYaudioists?

Any and all help greatly appreciated
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Old 22nd September 2009, 08:33 AM   #2
gooki is offline gooki  New Zealand
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Ok I'll try to answer your questions (all replies are to the best of my knowledge).

Quote:
Do you need to own a licence for the content to prevent HDCP working?
Not sure what your asking here.

Quote:
And/Or do you need to own a licence for HDCP decoding?
To manufacture HDCP compliant devices you require a licence.

Quote:
I have seen mentions of "membership" in order to build HDMI kit. Is this the case?
I believe a licence is all that is required.

Quote:
If content is unlicensed, is HDCP still a problem, or does it then become like any other digital interconnect?
Most sorces devices that are HDCP compliant demand HDCP even for encryption free content. The only way around HDCP is if your building the source and receiving devices (not overly practical).

Quote:
Can HDCP be physically hacked and is this illegal if you own content licences?
I vaguely recall something about HDCP strippers, but they were removed from the market pretty quick. As for legalities, I suppose that'll depend on the country you live in.

Quote:
And if HDCP is prohibitively expensive to develop, surely my best bet is to get a cheap HDMI receiver
There are other options. Standalone HDMI DAC boards are available (fully HDCP compliant) from a couple of manufacturers, which will be easier to mod if you want to replace the DACs/output stage etc. I have a prototype here that I'm looking to make available to the DIY community, so feel free to ask any questions and I'll do my best to answer (note i'm not overly technical, just someone with a few contacts in asia).

Last edited by gooki; 22nd September 2009 at 08:41 AM.
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Old 22nd September 2009, 12:30 PM   #3
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thanks so much - that was really helpful!
Any chance of a link/block diagram or somesuch of the prototype you mention?
You answered it later, but what I was asking first off was if owned licenced content used HDCP - as you said, most devices use it anyway. Since I want my DAC to be compatible with many devices I'll need to cope with HDCP.
Thanks again
Kit
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Old 22nd September 2009, 06:04 PM   #4
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Quote:
Originally Posted by gooki View Post
I have a prototype here that I'm looking to make available to the DIY community, so feel free to ask any questions and I'll do my best to answer (note i'm not overly technical, just someone with a few contacts in asia).
I wouldn't make too much noise about that if I were you or you might find your device on the key revocation list.
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Old 22nd September 2009, 07:37 PM   #5
gooki is offline gooki  New Zealand
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Quote:
Any chance of a link/block diagram or some such of the prototype you mention?
I don't have the schematics, but will try see what I can find, or I'll post up some photos.

Quote:
I wouldn't make too much noise about that if I were you or you might find your device on the key revocation list.
The video path maintains HDCP protection throughout the device, and I believe the audio output conforms to the HDCP requirements (will see what I can confirm here).
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Old 22nd September 2009, 07:43 PM   #6
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Searching about, I found this: http://www.lektropacks.co.uk/view_pr...85&sub1=&show=
This looks hackable, and fingers crossed is HDCP compliant (have emailed to check).
Its decoding looks pretty limited, especially from what I've read elsewhere. However that won't be a problem, will it? surely once the audio stream is separated I can just hook it up to my own decoding chips before then putting it through to my own DAC. Right?
It seems such a bloody fuss all this HDCP it seems almost easier to just buy a high-end receiver. I can't understand why it's so stupidly done - SPDIF is pretty terrible, but thew only alternative is almost impossible to access! Totally mad.
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Old 22nd September 2009, 08:44 PM   #7
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Quote:
Originally Posted by gooki View Post
and I believe the audio output conforms to the HDCP requirements (will see what I can confirm here).
Not if it puts out 8 channels of decrypted uncompressed digital audio.
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Old 22nd September 2009, 09:14 PM   #8
gooki is offline gooki  New Zealand
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Quote:
It seems such a bloody fuss all this HDCP it seems almost easier to just buy a high-end receiver. I can't understand why it's so stupidly done - SPDIF is pretty terrible, but thew only alternative is almost impossible to access! Totally mad.
I entirely agree. HDCP has done nothing to stop the spread of copy protected work. And is a major pain in the *** for the DIY community and small audio firms (even some major players like McIntosh didn't implement HDMI audio in their first HDMI based receivers because of the demands the licence requires).

Quote:
Not if it puts out 8 channels of decrypted uncompressed digital audio.
The output is analog, the end user would have to modify for digital if they wanted that (no different to modifying a full receiver).
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Old 24th September 2009, 12:05 PM   #9
NeoY2k is offline NeoY2k  France
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I wanted to make an HDMI receiver.
They reduced license cost, from 15000$ a year down to 10000$ a year!

Seems too much to me, and probably too much for a small company too unless there's some serious money to make with it.

That small box sounds great, should be easy to hack!
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Old 24th September 2009, 01:07 PM   #10
adelias is offline adelias  Greece
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It was hacked a while a ago.
http://www.switch-box.com/S_PDIF_ins...CLUX-11SA.html
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