Looking for a DIY DD/DTS decoder project

[stereoplay]

Hi,

is there any DIY project dealing with a DD/DTS (or EX 5.1 /7.1) decoder ?
I want to build up an pre amp with a decoder and 5.1 - 7.1 analog outputs for my power amp.


Thank you in advance.

Greetings
Frank

[netgeek]

There aren't any diy decoder projects because of all the licensing issues with Dolby, DTS et. al....... The best bet, if you really want something custom, is to rip apart a commercial receiver and make the modifications you want. I keep planning to get around to a similar project and I think a good starting point might be the new Creative Labs DDTS-100 which is made for low-cost setups using powered "PC-type" speakers. It costs around US$100 or so and that's probably what I'm going to use to experiment with. Seems to me that using some decent buffers, etc. around the decoder core might result in a fairly decent diy setup.

Too bad Analog Devices, Cirrus and the others can't sell the decoders in small quantities (with prepaid licenses) because that would be the best solution. As it is, Analog Devices has a great solution but the minimum buy is 1000 pieces. I might use a half dozen or so - so all we need now is a group buy for the other 994 parts.......

[RobPhill33]

I'm in..

[netgeek]

Originally posted by RobPhill33
I'm in..

Nobody else???!!! C'mon - we only need about 994 more and we're there!

[tiroth]

AD has a chip they sell to unlicensed developers? What is it?

[netgeek]

It's been quite some time since I looked (because I gave up but I'm fairly certain that it was AD. The search engine on their site is pretty good - give it a shot! My understanding from reading the fine print was that certain licenses were prepaid as part of the component cost - with the proviso that the minimum order qty. was 1000 pieces, non-cancellable/non-returnable. I'm sure that's to weed out the hobbyists and hacks - as well as to cover the paperwork involved, which is probably substantial.

[hifiZen]

I've worked on a few products containing DD / DTS decoders, and recall delivering prototype systems to Dolby Labs in San Fran for testing and certification... I believe this is a standard part of of their licensing agreements. The test criteria really aren't very strict, but it prevents really junk products from showing upon the store shelves with the DD logo plastered all over the front panel.

AFAIK, the OEM has to arrange separate licensing/certification with Dolby, and there is no such thing as a pre-licensed chipset that you can buy as an unlicensed user and plug into your product. Incidentally, decoder chips do seem to go through a certification of their own (at least ours did), and the chip manufacturer pays a licensing fee or royalty for each chip they sell which has the decoder enabled in the end product. I don't know if this is in addition to royalties paid by the OEM or just how all that works, but I am pretty sure the OEM needs to be licensed. Confused yet? Me too.

So I agree with netgeek - If you want a DD/DTS decoder, your best bet is to tear apart an existing piece of equipment and cannibalize the parts you need, or modify it for your own purposes. Likewise for HDCD decoders. My solution was to buy a DVD player with DTS decoder built-in. Then you can modify to your taste (usually pretty simple to do), including grabbing the I2S bus at the DAC... you could pipe this out to an external processor/DAC via LVDS. Someday, I'll peform surgery on my old Rotel CD player to extract it's HDCD chip, and then transplant it to a digital processor of my own design. Sadly, this seems to be the only way to accomplish this stuff. Perhaps some ambitious person will find some PC software with these functions and reverse-engineer it into some open-source software.

[Hybrid fourdoor]

Originally posted by hifiZen
Perhaps some ambitious person will find some PC software with these functions and reverse-engineer it into some open-source software.

But its still pretty bad when we have to do something ala DeCSS just to have fun doing something totally legal. I can understand their concern, but even THX has given in to quality control (Can you say THX cert cable......). Somehow I don't see how a $50 all-in-one DVD player is any less detrimental to Dolby's reputation than some folks homebrewing stuff. I mean Dolby could probably charge $50 for the chip alone and poeple woould buy it.

[netgeek]

Agreed - it's a shame that folks have to jump through hoops just to do something this simple. I guess I can understand the motives of the suppliers - they want to protect their IP and they also don't want to spend all of their time supporting a few end-users. The problem is that the least-competent (in terms of engineering skills) will be those who will use up the most of your support resources - and will likely generate the least return! So, as a manufacturer your only defense is to support a relatively small number of customers who are most likely to generate the largest returns - simple economics...

Still, it would be nice if there was some way to put the components in the hands of small volume users without the need for them to spend many mega-bucks in up-front licensing and legal fees. Who knows - it's possible (even if it's perhaps unlikely) that one or more of them could come up with a home-run product that even the "big guys" couldn't figure out... You never know...

In the meantime, hacking something like the DDTS-100 seems the only way to go if you're determined to roll-your-own. Bust in to the I2C bus or wherever practical and then have at it...

I'd be interested in sharing any notes/experiences, etc. with anyone here who wants to try it - I'm planning to do just that.

[netgeek]

Almost forgot - the software approach to this seems to be really close - the popular DVD players for PC's have the capability now - perhaps only a matter of time before the myterious/magical codecs slip into the hands of the public/open-software folks?