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Discussion Starter #1
Why are most streaming services have their movies in AAC stereo? I try playing it using dolby pro logic ii but it just don't sound as good as dts or dd. Any suggestions on how to get the AAC to sound better thanks.

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I take it then AAC isn't good for a home theater setup?

Who said that? AAC gives you 5.1 surround sound and is the audio standard on DVD's and the American digital TV-audio standard (ATSC 2.0). I listen to AAC a lot in my theater with no regrets.


As mentioned previously, AAC is bandwidth limited/reduced. You will get better audio from the advanced DTS-HD or Dolby TrueHD audio CODEC's found on BluRay discs, where disc space or spectrum don't limit the amount of bits that can be stored or transmitted.
 

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Discussion Starter #7
Who said that? AAC gives you 5.1 surround sound and is the audio standard on DVD's and the American digital TV-audio standard (ATSC 2.0). I listen to AAC a lot in my theater with no regrets.


As mentioned previously, AAC is bandwidth limited/reduced. You will get better audio from the advanced DTS-HD or Dolby TrueHD audio CODEC's found on BluRay discs, where disc space or spectrum don't limit the amount of bits that can be stored or transmitted.
So you use dolby pro logic then since aac is stereo?

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So you use dolby pro logic then since aac is stereo?

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AAC is not confined to stereo - as mentioned 5.1 surround is a part of the AAC spec:
https://en.wikipedia.org/wiki/Advanced_Audio_Coding


But to answer your question, when I do listen to stereo content, whether it be playing CD's or listening to stereo television, I do not engage Dolby Pro Logic/synthesized surround-sound. I have tried doing so but in my opinion, matrixing the side or rear channels changes the sound in a negative manner. But you (and many others) may enjoy the expanded sound-field Dolby Pro Logic creates and I wouldn't criticize you for doing so. Just know you are altering the sound and listening in a way the creator's did not intend.
 

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Discussion Starter #9
AAC is not confined to stereo - as mentioned 5.1 surround is a part of the AAC spec:
https://en.wikipedia.org/wiki/Advanced_Audio_Coding


But to answer your question, when I do listen to stereo content, whether it be playing CD's or listening to stereo television, I do not engage Dolby Pro Logic/synthesized surround-sound. I have tried doing so but in my opinion, matrixing the side or rear channels changes the sound in a negative manner. But you (and many others) may enjoy the expanded sound-field Dolby Pro Logic creates and I wouldn't criticize you for doing so. Just know you are altering the sound and listening in a way the creator's did not intend.
Well the main reason I am asking is the streaming service I use all there movies and TV shows are AAC stereo. I just was wondering if Dolby Pro Logic ii really make it into surround? I really enjoy surround sound just didn't know what my options was.

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Well the main reason I am asking is the streaming service I use all there movies and TV shows are AAC stereo. I just was wondering if Dolby Pro Logic ii really make it into surround? I really enjoy surround sound just didn't know what my options was.

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Yes, Dolby Pro Logic II really does create sounds for the side and/or rear channels/speakers from stereo sources. It does this by synthesizing or creating sounds from what is already existing in the 2 front channels. The downside is, audio reproduced in the surround channels is not discreet when synthesized. It is merely audio taken from the existing channels and manipulated to give the illusion of having more active channels/speakers. For example, taking the front channel information, adding echo or delay to each and sending this info to the side/rear channels is a form of synthesizing. The ears hear the sounds from the front and surround channels as being different, and thus an expanded sound field is created. But you will never say, hear a sound going around from speaker to speaker to speaker as if you were in the middle of a "circle of sound". You will not hear a helicopter flying from side-left to side-right from PLII and a stereo source.


If you enjoy the way Dolby PLII sounds on your system, in my opinion, you should say with that. I think your options for listening to your streaming service is either in sterero or PLII/synthesizing to create a surround environment. Another option is to listen in mono.
 

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Discussion Starter #11
Yes, Dolby Pro Logic II really does create sounds for the side and/or rear channels/speakers from stereo sources. It does this by synthesizing or creating sounds from what is already existing in the 2 front channels. The downside is, audio reproduced in the surround channels is not discreet when synthesized. It is merely audio taken from the existing channels and manipulated to give the illusion of having more active channels/speakers. For example, taking the front channel information, adding echo or delay to each and sending this info to the side/rear channels is a form of synthesizing. The ears hear the sounds from the front and surround channels as being different, and thus an expanded sound field is created. But you will never say, hear a sound going around from speaker to speaker to speaker as if you were in the middle of a "circle of sound". You will not hear a helicopter flying from side-left to side-right from PLII and a stereo source.


If you enjoy the way Dolby PLII sounds on your system, in my opinion, you should say with that. I think your options for listening to your streaming service is either in sterero or PLII/synthesizing to create a surround environment. Another option is to listen in mono.
I guess I will go with a service that offers ac3 or dts

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The thing about any codec is that you have two parameters that affect each other... the quality of the codec itself, and the bandwidth. AAC is an excellent codec and is capable of being audibly transparent if the bandwidth is high enough. Based on my tests, the point of transparency is just above 192 for stereo. I encode all of the music in my media server at 256VBR, just to be a notch over the line to be safe. So for multichannel, if each channel has a bandwidth of 128, it should be perfect sound. That is probably more bandwidth than the original poster is getting on his streaming service.
 

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But you (and many others) may enjoy the expanded sound-field Dolby Pro Logic creates and I wouldn't criticize you for doing so. Just know you are altering the sound and listening in a way the creator's did not intend.
Not necessarily. Back in the early 80s, a lot of prog rock engineers were fans of the Hafler-Doss Sum and Difference Matrix System. I remember Brian Eno talking in an interview about how he mixed all of his albums to use it. Basically, it was wiring the two rear channels with the proper positive left and right, but connecting the two negatives of the rears together. The result was to throw all of the elements of the mix that were out of phase to the rear channels. Since the out of phase material was totally different than the in phase material, there was no cancellation, and it would play fine with just two speakers.

I had my system wired like that back in the day, and many albums were clearly designed to be played like that. Some modern DSPs do pretty much the same thing. I wish the manufacturers of AVRs revealed what exactly their DSPs do. It would make it easier to figure out which ones to use and which ones not to use, But I guess that's a trade secret.
 

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Well it sounds like to me AAC is only good for music not movies
Sound fidelity is sound fidelity. It doesn't matter if it's music or a movie. AAC works fine for both. I use AAC with Handbrake when I convert movies and it works fine. You just need to have enough of a bitrate. Past the point of audible transparency you can throw more bitrate at it, but it won't sound any better.
 

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Well it sounds like to me AAC is only good for music not movies...
2Ch AAC can sound perfectly fine for movies provided it's been encoded correctly. And decoded correctly.

I've noticed that some UK 'live streaming' (DVB-T2) services are using HE-AAC v2 (Parametric Stereo). Which sound awful if your smart TV can't decode them streams correctly but perfectly fine if your smart TV can.

Bamafan35611: Out of interest, what device are you using to access and view these movies. And which 'service' are they on?
 

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AAC was designed as the successor to mp3. Bit-for-bit (edit: bitrate, that is), it should sound better than the very old dts or dd codecs (especially the latter).

As Andre Smith mentioned, AAC can even do surround (up to 7.1), but would lead to compatibility issues with home theater set-ups. i.e.. if there is no center speaker, the user could potentially hear no dialog, while a Dolby receiver would know to mix/route the center info to the mains.

However! One point of interest is how the new Apple TV 4 treats surround content. By decoding the surround content "in the box" and before sending it downstream to the receiver, Apple technically has the ability to distribute surround content via AAC or some other codec (Apple Lossless? One can dream!) :)
 

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Discussion Starter #18
I just don't get it. Even the coverage of the Olympics on the NBC SPORTS app is in AAC. You would think in 2016 it would be at least ac3 by now.

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I just don't get it. Even the coverage of the Olympics on the NBC SPORTS app is in AAC. You would think in 2016 it would be at least ac3 by now.
AAC can sound every bit as good as AC3 at lower bit-rates.

The major issue with AAC is that media playback device manufacturers don't offer the option to pass AAC as a bit-stream via SPDIF or HDMI and surround sound amplifier manufacturers don't offer the ability to decode AAC as a bit-stream via SPDIF or HDMI.

So at the present time media playback devices such as televisions and set-top boxes have to transcode (multi-channel) AAC to (multi-channel) Dolby Digital internally prior to passing the AC3 bit-stream via SPDIF or HDMI. And some playback devices do this transcoding better than others!
 

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Discussion Starter #20
I gave a denon avr 591 so I won't hear the best sound from aac right??

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