Originally Posted by Roger Dressler
Yes, but Netflix is not going to do that. You saw in the cited blog post how bitrate is a factor for many users who live with service caps.
Exactly, which is why they have the quality limit setting, but caps are not a factor for many other people. I have a cap for my 25 Mbps Cox cable modem service but it's 250GB/month; with all of my downloading and streaming I rarely exceed 175GB. Netflix let's you limit the highest bit rate encoding that they will send you, but if you choose the highest setting, they will send you up to 4800 Kpbs 1080p video plus 384 Kbps DD+ sound, if bandwidth available on your connection to their server is high enough and your device is 1080p and 5.1 capable and the title you're streaming has those encoding available (you'll get the 384 Kpbs DD+ with 3600 Kbps 720p if your device is 5.1 capable and not 1080p capable; most titles with 720p video encodings seem to have 1080p encodings as well but only a relative handful have 5.1 sound). I've measured average bandwidth consumption while streaming from Netflix and the numbers are in line with those.
You might be right, but how do you know? One way to tell is if your AVR has a bitrate display for the DD stream. If is is DD384, it is native DD. if it is DD640, it is converted from DD+.
My AVR cannot display sound encoding bit rate, so my only judgement is how it sounds compared to another device bitstreaming the DD+; I've played both simultaneously and switched back and forth and the basic DD from the PS3 compares poorly. As I stated, I like the sound of the 192 Kbps stereo better--it just seems fuller and punchier.
If your HDMI/DD-capable AVR could not play audio from the Roku, that pretty much conforms both points: Netflix is sending DD+ to the Roku, and it has no internal Dolby decoder/converter.
Yes--which is why I say that they may be a doing a disservice to their customers by using DD+. My HDMI switching AVR w/o DD+ decoding was only 5 years old (from an Onkyo HTiB package). Surely there's lots of similar equipment still in use. I was willing to upgrade, because I'd been thinking about doing it for a couple of years, but not everyone is. All of my other digital surround equipment which deals with advanced sound encodings can internally decode them into LPCM, which my old AVR could handle, so I'd never needed
to upgrade for anything before the Roku 2.
Is there any device that cannot?
Plenty--I have 6 devices which can stream Netflix: the Roku 2 XS, PS3, Panasonic BD player, TiVo Series3, Xbox 360 and this PC (which is connected to the same 1080p LCD panel and AVR as the rest of that stuff). Of those, only the Roku, PS3, BD player and Xbox can stream the 5.1 sound, and the Xbox has only had that capability since the December dashboard update. I'm sure that the great majority of pre-2011 streaming STBs, BD players and televisions with embedded Netflix players (and probably most 2011 ones) still cannot stream the 5.1 sound and only a very small handful can stream the 1080p encodings which debuted on the PS3 at the same time.
The DD+ signal is not build on a DD core. That would not save bitrate. But DD+ was designed to use much of the same structure as DD specifically so it could be converted without losing a generation as happens with transcoding.
Use of an extractable core always seemed unlikely to be more efficient to me, but Dolby's literature is confusing on that point. From this
Warning: Spoiler! (Click to show)
Warning: Spoiler! (Click to show)
Dolby Digital Plus, by contrast, uses a “core plus extension” structure, a new and unique technique to address downmix compatibility. The core is a complete 5.1-channel mix, while an extension contains any additional channels.
With 7.1-channel content, for example, the Dolby Digital Plus bitstream contains a core audio packet with a 5.1 mix, plus an extension audio packet containing the original 7.1 mix’s separate Left Surround, Right Surround, Left Back, and Right Back channels. To ensure that no surround information is lost in 5.1 playback, the surround channels of the 5.1 mix are downmixed from the separate surround and back channels of the original 7.1 mix. For 7.1 playback, the Left, Center, and Right channels of the core 5.1 packet are used, but its two downmixed surround channels are replaced by the four separate surround channels from the extension packet. There’s no need to include a separate stereo (two-channel) mix because all Dolby Digital decoders can create a stereo mix from a 5.1 mix on the fly.
Thus Dolby Digital Plus supports both 5.1 and 7.1 presentations without the need for rematrixing and its potential for negative side effects. The high coding efficiency of Dolby Digital Plus—coupled with the large capacity of the Blu-ray Disc format—means there is no real penalty for the resulting 9.1-channel load: Dolby Digital Plus can deliver 7.1-channel soundtracks with superb quality at bit rates of 1 Mbps or less.
The statement, "the core is a complete 5.1-channel mix" is what had me confused.