Home > Uncategorized > Controlling Volume… Look Ma, no extra Wires!

Controlling Volume… Look Ma, no extra Wires!

Wow, I hate extra cables.  It turns out I have a little Obsessive-Compulsive Disorder and I am compelled to simplify everything around me.  I like to joke that all good engineers have a little OCD.  But, one of the things that bugs me is that when I pop in a Blu-Ray and enable that magical Digital True-HD audio through my surround sound AV Receiver, my computer volume suddenly has no effect because audio is digitally passed through to the receiver.  So, the computer cannot modify the audio stream to change the volume.  The natural solution is to use the AV Receiver to exclusively control the volume.  My remote control and most other universal remotes can emit simple IR codes to control the volume, but I wasn’t satisfied with this.  The main reason was that I wanted to control the volume from the kitchen, but I didn’t have line-of-sight for the IR to work.  The RF would raise and lower the computer volume, but not for any digital audio like DTS and TrueHD.  So I used my USB-UIRT with a nice program called Intelliremote to repeat the IR codes to the AV Receiver, but there was terrible lag that sometimes led to disaster with the Receiver volume appearing to be possessed by demons for 10 seconds after a volume change if you held the button too long.  So, one day, I came across an HDMI-CEC USB bridge device and was immediately struck with the dream of controlling all of my devices through the magic of the HDMI cables that already connect them.  So, on a whim and looking for a fun project, I bought the thing.  A few days later, I got it and I’ve been playing ever since. 

I first plugged it in with USB and immediately looked up the command to increase volume and it worked!  But, even though I had plenty of HDMI ports on my Receiver, I wanted the computer itself to be CEC enabled, not an external box (OCD again).  So then, I thought, wouldn’t it be great to have a CEC enabled graphics card?  Oh yeah!  So since the only card with HDMI outputs and support for TrueHD digital Audio was the new ATI 5xxx series, I got one of those and created what is probably the world’s first HDMI-CEC enabled graphics card.  

Behold, the first HDMI graphics card with CEC and Digital Audio!

All that was needed was a free internal USB header to plug the CEC bridge board into.  DISCLAIMER: WARNING – doing this voids all kinds of warranties and if you do it wrong, you can probably fry stuff.  But anyway, it worked!  Unfortunately, the Catalyst drivers didn’t work well for me with Media Center and after a month I abandoned this.  I moved on to one of the only other ways to get 1080P video and TrueHD audio.  That was the chipset integrated Intel Audio and Video (although I think it’s all Realtek based).  But to make that work, I had to solder to the CEC bus on the underside of the Motherboard (another warranty voider). 

Soldering to the CEC bus on the Motherboard



RainShadow Tech’s CEC Bridge Mounted Internally

While trying different ways of connecting the CEC Bridge, I started on my specialty, the software.  Below are some screens followed by a video of CEC in action!  Now, the software works most of the time, but for anyone else to use it, it has to work 100% of the time.  At some point soon, I’ll have to recruit some testers…  Hopefully, this will get recognized by the industry as awesome and get integrated into products.  I’m open to ideas! 



I’m not very good with the camera, but you’ll see how CEC wakes up the TV and AV Receiver, setting them to the correct inputs.  Then CEC control of the volume.

Categories: Uncategorized
  1. Mike Horvath
    March 17, 2011 at 11:03 am

    I read this when you first released it, and now i am at the point where i will also need to start using something like this to automate some of the devices connected to my HTPC. I would gladly test for ya (in the process of getting a interface device, sold out for now). Also, i was wondering if you have made any more progress sicne the link i have is onyl to this page.

    • March 17, 2011 at 7:53 pm

      Actually, there has been quite a bit of progress since I posted this. There is a discussion forum, screenshots, and a download page at valkyrietech.com.

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