A Terror Story of Dolby Digital

This is a story I wouldn’t typically share, especially on my blog. The reason being that I wouldn’t want to look uneducated in the eyes of my viewers or potential clients. Unfortunately, I need to share it because of its hysterical and educational value. I am a large fan of first person shooter games. One way to gain an advantage over your opponents is to monitor your audio in surround. This way, when an enemy is walking up behind you, you hear them and turn before they shoot. In stereo, you can only tell if an enemy is approaching you from left or right, whether it’s in front or behind you.

I am currently in the process of setting up a sound design studio that offers 5.1 mixing. I had the brilliant idea of setting up my Xbox 360 with my Pro Tools rig through a Digidesign 003 interface. “This is totally going to be easy,” I said to myself as I was extremely confident in my understanding of signal flow and transfer. I bought an adaptor for my somehow outdated white Xbox that allows simultaneous audio feed from an HDMI cable and an optical (adat, lightpipe, etc.) output. So all I should have to do is run an optical cable from my Xbox to my 003, right?

WRONG!

I tried everything to get signal to show up in my Pro Tools session, even things I knew couldn’t possibly work but had small hope they would. I tried digging around Google and the Avid support forums for assistance, but nobody was attempting the same things. Except for one other individual, who must be a genius because he had the same thought as me. Reviewing his post and the responses he collected, I learned that Dolby Digital (the signal my Xbox produces through the optical port) needs to be decoded so an optical input can understand its routing. This is why your home receiver will read DTS, Dolby Digital, or Dolby Pro Logic 2 when you start your DVD or Blu-ray player. It has the decoder built in and automatically understands any signal that passes through.

Now that I knew the problem, the rest should be a piece of cake, right? Once again, the answer is a huge WRONG! I did much more research to determine how decoding the format works and what devices will help me in Pro Tools. I either need to buy the Neyrinck SoundCode Dolby E Decoder RTAS plugin to decipher the signal as it comes in, or buy another piece of external gear. The external box takes an optical (either lightpipe or coaxial) signal, decodes it, and sends it to 6 RCA connections, which can than be attached to my 003 with RCA to ¼” cables. The plugin option costs $3,495, while the external box, which is the HDCVT HDV 18A, costs $99.

This has become a pretty much no-brainer situation. $3,495 just to hear my opponent run up behind me is a little drastic. There’s a great lesson that comes out of this though. I have always understood that I needed to encode a 5.1 mix if a client wants Dolby Digital, but never understood why. I always assumed it was just part of the process and that there was no rhyme or reason except to give it that Dolby Digital title. The lesson to be learned is to never assume something in audio is done a specific way for NO REASON. Everything in audio engineering is done for a reason, and it took much research and frustration to determine it. For all of you audio engineers out there, make sure you understand what you’re doing before you do it. You don’t want to post an embarrassing story like mine!