Historical view of DSU and usage by PC users
Many of you have noticed the release of DSU, but I do not see anyone noticing its arrival on the market, from the more limited release in PC software.
To my knowledge and observations, the direct precursor to DSU is the Surround Decoder, included in Dolby® PC Entertainment Experience v4 (PCEE4), released in 2010. Unlike the previous version of the software, which included Pro-Logic technology, this up-mixer was described as “next-generation frequency-domain matrix surround decoder”, which "Unlike previous wideband technologies, the Surround Decoder operates on a multitude of perceptually spaced frequency bands for finer grain analysis and the ability to steer different frequency bands individually. The result is surround sound with precisely located audio elements and a spacious ambience rendering (that is, the part of the audio that is ambient—indirect, diffused sound—is spread around to make that part of the audio more enveloping)."
This Surround Decoder was subsequently included in later iterations of the software (Dolby Digital Plus for Windows/DS1, Dolby Audio/DAX2, Dolby Atmos for Windows/DAX3). In this year, the app was updated to support height channels (Dolby DAX API version 3, with Dolby XML version 3.3).
What that means to most of us?
Installing the app allows for usage of the DSU (if it was described properly by this forum users to perform similar actions as the surround decoder) on many more systems than is currently present in new Atmos receivers.
If the app is configured on an HDMI endpoint, Surround Decoder generated 5.1/7.1 LPCM can be delivered.
If the app is configured on an S/PDIF endpoint, Surround Decoder generated 5.1 LPCM can be encoded as AC3 and delivered (Dolby Digital Live). Such usage allows for really enhanced up mixer to be used instead of Pro-Logic, or on other cases, up mixing via manufacturer's software, which can be the case on cheap HTIB or soundbar.
The configuration on how to use height channels are not currently known to me, though I noticed its presence on
The surround decoder really does some magic on lossless stereo content. All previously used up mixers by me is using all speakers constantly, with steering allowing for louder content at some speakers at a time. But, it does not completely separate the audio into discrete channels.
Dolby surround decoder seem to do the impossible on music. Main vocals are most often sent on the centre channel (I do not recall any instance where that has not happened). They do not bleed out to any other channel, that is instruments are present in the rest of front and side channels, with no main vocal. The instruments themselves are further separated between the channels. The front channel may play one instrument, while the side channel plays another. Again, no audio bleeding occurs. If we listen on a single channel at a time, it seems that they play one single instrument at a time.
Ambiance vocals are often spread to side channels. Even if a main vocal and ambiance vocals are present at the same time, they are clearly separated between centre and side channels.
It feels that the music was mixed for 5.1, as each channel is dedicated for its own content.
Lossy audio does not fare as well. The actions of separating content are harder, as quantisation noise do disturb the work of the decoder. Side channels, though appear to have separate content, do get a major amount of noise. At times, the audio cannot be clearly delimited between channels. There I do feel that a simpler decoder could do a better job, as the quantisation noise would not be so concentrated. Still, when sitting in the proper position, the noise separation is not that pronounced.
Similarly to DSU, this decoder does not have separate music/movie mode.
I did not test the decoder on stereo movie audio.
I am currently using a simple HTIB, that can only receive 5.1 audio via AC3 encoding. Thus, I am using Dolby Digital Live technology to deliver the results of the decoder to the receiver. I am currently using the Dolby Atmos app for Windows (DAX API v3.2), configured for 3 front speakers, 2 side speakers, 0 height speaker and with subwoofer present. (these are options that can be set in the Dolby configuration XML file)