Unable to get VLC or QuickTime to play 7.1 audio even though the 7.1 speaker configuration works correctly

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Level 1

4 points

Unable to get VLC or QuickTime to play 7.1 audio even though the 7.1 speaker configuration works correctly

HI folks

I'm new to Macs and, therefore, new here, so please forgive me if this is posted in the wrong place, but I have spent the day trawling the Internet and even been on the customer support chat for several hours and still unable to solve this problem.

I have an October 2015 iMac 27" 3.2GHz with 8gb RAM, which I have bought and connected up today. I have it connected to my Pioneer SC LX88 AV Receiver (AVR) via HDMI cable from a Mini DisplayPort adaptor in the back of the monitor (Belkin model adaptor capable of passing up to 4K through it). The very same HDMI cable has just been unplugged from a Windows system where I was playing HDMI audio into the same Pioneer AVR and getting 7.1, True HD, etc. and the display on the AVR would say things like PCM for 7.1, or Digital when watching Netflix through the Windows app. However, now it's plugged into the Mac I just cannot get VLC or QuickTime to play the rear channels of sound when running a Dolby sound test file (even though the AVR is showing PCM). When I tinker with the Midi settings and configure the speakers in the "7.1 Rear" setting I am able to get the white noise sound from all 8 channels, so I know that the sound is being output to the AVR correctly; it just seems to be the media players that cannot output all 8 channels when playing the sound tests. The oddest thing is that when playing these Dolby sound test files (which I double-checked on another system to be True HD) through VLC or QuickTime and getting the 5.1 audio, I am able to click on the rear speakers in the configurator and get the white noise from the rear speakers while the 5.1 audio is still playing on the other 6 channels, so it surely can't be my setup.

However, Apple support were unable to help and recommended that I go to Pioneer (the manufacturers of the AVR) and ask them. This seems counterintuitive to me, so several hours of assistance where wasted.

Please can anyone help help out a Mac noob?! Everything is up to date and running on the latest OS.

Apologies for the long post, and thanks in advance!

iMac (Retina 5K, 27-inch, Late 2015), macOS Sierra (10.12.1)

Posted on Oct 29, 2016 5:53 PM

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Answer 1

AnderPsych Author

Level 1

4 points

Oct 31, 2016 10:33 AM in response to AnderPsych

Some updates to report:

I just checked the two Dolby sound test files I have been using and have some more info to add.

The first file (True HD mkv file, which cycles all speakers by position) plays only as 5.1 on VLC instead of the necessary 7.1, and sounds a bit distorted but will not play properly on QuickTime (it converts when you open it and then plays without any audio at all, even though the video is spot on).

The second file (Dolby Atmos m2ts file) plays with proper 7.1 through VLC without distortion (showing maybe an issue with the other MKV file) but only plays in 5.1 on QuickTime.

Whether this adds anything helpful at this stage, I'm not able to tell. I shall try to track down some other audio test files, though.

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