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User profile for user: Johnb-one
Johnb-one Author
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surround sound and Audio MIDI setup

Just a silly question. I have a Mac Pro running 10.14.6 (mojave). I was wondering if I could get surround sound out of it for everything, not just certain movies. I have tried running Audio MIDI setup, the latest version( 3.3) and although for outputs, I see a number of different frequencies (44/48/96) and bit depths (16/20/24) on both the analog and digital outputs, I can't seem to get it to do 5.1 sound, not under Audio MIDI setup anyways, Under speaker setup, I either get stereo or 2.0 surround, which is sorta the same thing. There is no option for multichannel surround sound as far as I can see. I do understand that only certain things have surround sound info, eg movies, and most of the time it's stereo only.... Still, the option would be nice to have. I have a set of Logictech Z906 speakers, with the decoder built into the subwoofer, and a control box sitting on my desk, which is also connected to the decoder, for picking inputs, levels, and controlling the volume. and my trusty mac pro. I don't know if this is a hardware question or a software one, so that's why I posted it here, under the "Mojave" section. and yes, it's been that way since at least sierra, maybe mavericks......Hmmm...thanks for any insights/help


john b

Posted on Aug 21, 2019 4:56 PM

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User profile for user: Midi is anger
Midi is anger
User level: Level 1
39 points

Posted on Aug 26, 2019 1:01 PM

SPDIF (the optical output also referred to as TOSLINK) is limited to 2 channel audio when using PCM, I could go into a longer explanation about the history of it but.... SPDIF doesn't have the bandwidth. PCM is the default audio format that computers process audio.


You can pass-through non-PCM bitstreams like Dolby Digital and DTS via SPDIF which pre-HDMI was the way multichannel audio was carried, then it can be decoded by an external source such as a receiver that support Dolby Digital. The way game consoles like the, PS2 and Xbox, Xbox 360. PS3 functioned is they had a real-time encoder convert the multichannel sound to Dolby Digital or DTS. Windows with certain audio setups had this ability too via Direct Sound. Mac OS has no equivalent for this real time codec encoding for audio.


VLC allows you to pass bitstream like Dolby Digital, DTS and AAC but this is entirely contingent on if the source has one of these formats.


Audio/Midi Set up allows as many I/O channels as your computer has, and can aggregate them into groups (say a recording interface that has 10 inputs and ouputs) but macOS does not have support for decoding Dolby Digital, DTS and multichannel-AAC to said interfaces. Even if it did, SPDIF is bandwidth limited. Ironically, you can master a 5.1 or 7.2 movie using macOS with the correct hardware and software as you'd be using discrete I/O but still wouldn't be able to play it back without an external decoder once the audio had been converted to one of the many flavors of DTS or Dolby Digital codecs.


If your Z906 have a Dolby Digital?DTS decoder then using VLC, selecting the output stream as the SPDIF output. For all other applications, you'll only get stereo with SPDIF.

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User profile for user: Midi is anger
Midi is anger
User level: Level 1
39 points

Aug 26, 2019 1:01 PM in response to Johnb-one

SPDIF (the optical output also referred to as TOSLINK) is limited to 2 channel audio when using PCM, I could go into a longer explanation about the history of it but.... SPDIF doesn't have the bandwidth. PCM is the default audio format that computers process audio.


You can pass-through non-PCM bitstreams like Dolby Digital and DTS via SPDIF which pre-HDMI was the way multichannel audio was carried, then it can be decoded by an external source such as a receiver that support Dolby Digital. The way game consoles like the, PS2 and Xbox, Xbox 360. PS3 functioned is they had a real-time encoder convert the multichannel sound to Dolby Digital or DTS. Windows with certain audio setups had this ability too via Direct Sound. Mac OS has no equivalent for this real time codec encoding for audio.


VLC allows you to pass bitstream like Dolby Digital, DTS and AAC but this is entirely contingent on if the source has one of these formats.


Audio/Midi Set up allows as many I/O channels as your computer has, and can aggregate them into groups (say a recording interface that has 10 inputs and ouputs) but macOS does not have support for decoding Dolby Digital, DTS and multichannel-AAC to said interfaces. Even if it did, SPDIF is bandwidth limited. Ironically, you can master a 5.1 or 7.2 movie using macOS with the correct hardware and software as you'd be using discrete I/O but still wouldn't be able to play it back without an external decoder once the audio had been converted to one of the many flavors of DTS or Dolby Digital codecs.


If your Z906 have a Dolby Digital?DTS decoder then using VLC, selecting the output stream as the SPDIF output. For all other applications, you'll only get stereo with SPDIF.

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surround sound and Audio MIDI setup

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