In reading through the many postings under this topic, I've come to two conclusions. First, those of us who are experiencing the problem are connecting video and audio from a Roku device to an HDTV (e.g. 1080) via HDMI, and then passing audio via TOSLink to a "legacy" AVR that supports only the original AC-3 Dolby surround format. In my case, it's a Vizio TV fed by a Streaming Stick +, and a Denon receiver. My second conclusion is that this appears to be a Roku problem to solve.
It appears to be a Roku problem because, as many have pointed out, legacy Dolby 5.1 USED to work with our older equipment until the firmware update. It would be quite a coincidence for Netflix and Amazon to have made their audio bitsteams incompatible at exactly the same time as the Roku firmware update, but Roku blames the problem on these services and not the device. We all understand that Roku devices only pass through the audio bitstreams, but there is supposedly a compatibility path with DD+ bitstreams (see below), and apparently, many Roku models were serving up a compatible stream until this capability was turned off. If not a regression in firmware, one is tempted to ask whether turning off this capability was deliberate, perhaps demanded or orchestrated by the content providers.
There are many shiploads of perfectly functional legacy surround sound systems owned by Roku customers who don't need or want 8 channels or the other "features" of these new formats. Roku's TannerD offers a sure solution, the only solution according to Roku -- buy a new receiver -- thereby, among other things, needlessly promoting the accumulation of yet more toxic electronic waste.
So Roku, please either fix this widely reported downgrading of functionality, or explain, truthfully, why it was turned off. Thanks.
Some of you might be interested in what Dolby says about Dolby Digital +, also known as E-AC-3. This is from a technical document available on Dolby's site:
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The increased channel capacity [of E-AC-3] is obtained by associating the main audio program bitstream with up to eight additional substreams, all of which are multiplexed into one E-AC-3 bitstream. This allows the main audio program to convey the existing 5.1-channel format of AC-3, while the additional channel capacity comes from the dependent bitstreams. This means that a 5.1-channel version and the various conventional downmixes are always available.
The E-AC-3 system provides an effective method to convert an E-AC-3 bitstream to an AC-3 bitstream to ensure compatibility with the large installed base of AC-3 decoders. The conversion process is designed to minimize loss in audio quality while keeping the complexity at a level suitable for low-cost consumer devices.
