The new Blu-ray DVD and HD-DVD players hitting the market are introducing two new audio formats along with their high-definition video capabilities. DTS-HD and Dolby TrueHD audio formats are available on almost all medium-grade and higher-end audio receivers, and they are now a standard feature on almost all Blu-ray and HD-DVD players. Many people are familiar with the Dolby name from such audio formats as Dolby Surround Sound, while DTS-HD comes from a company called Digital Theater Systems Inc.

So what are DTS-HD and Dolby TrueHD all about? Let's start with DTS-HD first. There are two different versions of this new audio format-- DTS-HD High Resolution Audio and DTS-HD Master Audio. Both are extensions of the original DTS audio formats. The difference between the two is that DTS-HD High Resolution Audio is a "limited" version of DTS-HD Master Audio. Below is a list of what these two versions feature:

DTS-HD High Resolution Audio

• Delivers up to 7.1 channel audio
  
• Transfers at 96khz sampling frequency
  
• 24-bit depth resolution
  
• Bit rates ranging from 6.0Mbit/s to 3.0Mbit/s
  
• Used as an alternative to HD Master Audio if disc space isn't sufficient
  
• Only available for Blu-Ray/HD-DVD
  
• Down-mix capable

DTS-HD Master Audio

• Virtually unlimited number of surround channels
  
• Transfers at 96khz sampling frequency
  
• 24-bit depth resolution
  
• Blu-ray supports 24.5Mbit/s
  
• HD-DVD supports 18.0Mbit/s
  
• Down-mix capable to 5.1 and 2 channel

Dolby took the same road as DTS by having two versions of its new audio format to choose from-- Dolby TrueHD and Dolby Digital Plus (or Dolby Digital +). Dolby TrueHD is the "better" format of the two, with Digital Plus considered to be a "smaller" version.

Dolby Digital +

• Mutlichannel output (up to 7.1)
  
• Up to 6Mbps Bit rate
  
• Can be used with both HD/Blu-ray DVDs and standard DVDs

Dolby TrueHD

• Supports up to 8 channels
  
• 18Mbps Bit rate
  
• 100% "Lossless" Audio
  
• 24-bit depth resolution
  
• Transfers at 96khz sampling frequency
  
• Down-mix capable

Dolby Digital + is compatible with both regular DVDs and Blu-ray/HD-DVDs. The main goal of Digital + is for it to be a more universal audio format for regular DVDs and the new high-definition ones. Dolby TrueHD, like DTS-HD Master Audio, is an actual bit-per-bit replica of the original studio mix, which of course is how the director intended you to hear the sound. This wasn't possible before, due to the lack of space on a normal DVD. With the newer Blu-ray and HD-DVDs, more space is available.

To enjoy the benefits of DTS-HD and Dolby TrueHD, you must have a Blu-ray or HD-DVD disc that has been recorded in these formats. You will find a label on the back of the disc stating whether it is DTS-HD or Dolby TrueHD capable. Most older movies won't have these audio features, but newer films are being recorded in these formats.

Next, you need to have an HD-DVD or Blu-ray player that can decode and output DTS-HD and Dolby TrueHD. You'll also need an audio receiver that can process these signals. The receiver is probably the most essential part, because if you're seeking TrueHD/DTS-HD you need your receiver to process/output the sound. Also, the signal can only be passed via an HDMI (High-Definition Multimedia Interface) cable. Optical and digital coax cables are not capable of transmitting these audio formats. The cable needs to be HDMI version 1.3 (all the Audioquest HDMI cables we sell at Abt are version 1.3).

Both Dolby and DTS claim their new formats reproduce audio the way the director meant it to sound, so this is where it boils down to the individual listener. You can throw around a whole lot of numbers, but people want to actually hear the difference. Most people report that they hear a positive upgrade in sound quality from older audio formats when comparing them to these new HD formats.

After comparing DTS-HD and Dolby TrueHD on multiple movies ranging from "Transformers" to "300" (movies we thought would deliver the best surround-sound experience), we decided that one format isn't noticeably better than the other, although they both clearly sounded better than the older audio processing formats. The vocals were clearer, the explosions seemed more intense, and a spear flying past King Leonidas's head felt like it was being thrown past ours.