The appetite for high-definition TV shows and movies from streaming services had led to the adoption of new technologies. These technologies are not only driven by technical requirements but also by marketing and financial ones. Unlike its physical media counterparts such as DVDs and Blu-rays, however, video streaming cannot depend on a reliable and consistent amount of bandwidth to deliver the full potential of high-quality audio and video.
To best simulate the theater experience, two new audio codecs–Dolby TrueHD and DTS Master Audio–were developed to accurately reproduce a film’s soundtrack. Both are bandwidth intensive. A Dolby TrueHD soundtrack can pump out as much as 18 megabits per second. The typical high-speed Internet connection for the home is about 5 MBps. Well-suited for Blu-ray, it is not good for streaming movies over the Internet. Both for this scenario and for the coming of digital broadcast TV, Dolby developed a new codec known as Dolby Digital Plus.
Dolby Digital Plus offeres the advantage of providing the same quality audio as Dolby Digital but with less bandwidth. With additional bandwidth, Dolby Digital Plus can provide higher quality audio than Dolby Digital, utilizing up to 6 MBps of bandwidth. Dolby Digital Plus can also provide up to 7.1 channels versus Dolby Digital’s 5.1 channels. There’s a good comparison of Dolby’s surround formats on their website (click on the Compare tab).
For some time, most consumers haven’t been conscious of the difference between Dolby Digital Plus and Dolby Digital. Back in 2008, Dolby Digital Plus was starting to roll out and, while most A/V receivers couldn’t decode it, it didn’t matter. Home theater components had a variety of ways to deliver surround sound to the receiver: multi-channel analog connections (RCA), digital audio via S/PDIF, and HDMI. These components typically had built-in decoders that could convert Dolby Digital Plus to Dolby Digital or send the signal over multi-channel analog connectors. This is how compatibility was maintained with legacy A/V receivers. As newer receivers became available with the ability to decode Dolby Digital Plus, it made the decoders on the other home theater components redundant.
For mass-market consumer electronics, there is a race to lower manufacturing costs and hit lower price points. As a result, we’ve seen the elimination of multi-channel RCA outputs on Blu-ray players and the removal of component video outputs on Blu-ray players and streaming boxes such as the Apple TV and Boxee. Compared to its predecessor the Roku XDS, the Roku 2 XS eliminated both component video and the digital optical audio port (S/PDIF). The Roku XS also added the ability to play games in an effort to differentiate itself from the sea of streaming devices. While copyright protection was one driver to eliminate some of these connectivity options, I think it’s also driven by the need to reduce manufacturing costs.
Parallel to this development, two of the major streaming video streaming services, Netflix and VUDU, chose Dolby Digital Plus to deliver surround sound (Amazon Instant uses Dolby Digital). Components with S/PDIF could still potentially deliver surround sound. However, since S/PDIF only has enough bandwidth to deliver regular Dolby Digital, the component would be responsible for converting from Dolby Digital Plus (as referenced above). Technically, it’s easy, assuming the manufacturer licensed the technology from Dolby, which in turn, adds to the cost of the box. Netflix boxes that provide this feature include the Apple TV, the WD Live Plus, and the Playstation3.
Back to the Roku 2: It has a new Netflix client that offers surround sound via Dolby Digital Plus. If the Roku 2 had an S/PDIF port, it would have to convert Dolby Digital Plus to regular Dolby Digital (well, maybe it wouldn’t have to, but it would set an expectation that it did). This would require additional licensing costs. By only passing-through (bit-streaming) Dolby Digital Plus over HDMI, the Roku 2 does not have to do any audio processing, cutting down on its costs.
So, my guess is that we’ll see the S/PDIF port start to disappear on the next generation of streaming boxes as well as Blu-ray players. That’s great since it lowers the cost of the box unless you have an older receiver.
The end result is that only one component in your home theater needs to decode surround sound: your receiver (or processor if you have a higher-end system). If you’re starting from scratch it should lower the total cost for putting together a home theater. However, if you already bought a receiver, it may or may not support Dolby Digital Plus. You would think that any receiver with HDMI connections would support Dolby Digital Plus but that’s not the case.
Since Dolby Digital Plus is a relatively new codec, even some recent receivers aren’t compatible. Major manufacturers started adding it to the higher-end models in 2008. It wasn’t until 2010 that entry level receivers from popular consumer brands such as Pioneer and Onkyo added Dolby Digital Plus. Like an HDTV, most folks don’t buy a new receiver every couple of years. All of this can be frustrating if you just purchased a receiver in the last couple of years and it doesn’t support Dolby Digital Plus.
So, while we have a more efficient system to deliver high quality surround sound, it may cost you some extra bucks in the short term. If you want to enjoy the best sound possible from video streaming services, it may be time to pick up a new receiver. Alternatively, grab one of the existing media streamers on the market before they eliminate the S/PDIF port once and for all. Then again, you could just keep buying Blu-rays.