mid-2011 MBA HDMI audio output (5.1)

For those that don't know, I had an issue with my 13" MBP being able to output multi-channel audio to my old speaker system hooked up via HDMI. For whatever reason, it would only output 1.1 audio (i.e. mono and a dedicated subwoofer channel) to that. I have since purchased a new surround sound system and everything was fine. My 2011 13" MBP could output audio to be decoded by the receiver (i.e. DTS 5.1 or Dolby Digital 5.1) along with stereo PCM for simple stereo music. That would allow me to apply either Dolby Prologic II or Neo mixing to it. I actually preferred that when listening to music so everything wasn't coming from just the front and right speakers.

I have since sold my MBP and purchased a mid-2011 MBA and I am having a difference experience. Right from the beginning, it has been outputting 5.1 PCM audio to my receiver. Now, that works for audio/video sources with 5.1 channels as I can directly play those in QuickTime or VLC without forcing my receiver to decode the audio (same results as before, just the Mac is decoding the Dolby Digital or DTS 5.1 to PCM 5.1). However, the problem is that it is outputting PCM 5.1 audio no matter what. This means that, whenever I listen to music, it comes from only the front left and right speakers. Also, since my receiver is getting a 5.1 digital signal, I can't apply Dolby Prologic or Neo to it (which are settings through the receiver).

It didn't work that way the first day I took my MBA home but it now only outputs 5.1 PCM audio no matter what I play. I can't change the settings for this either as there aren't any audio options for HDMI output. Is there a way to just force my MBA to output 2.0 audio via HDMI? I don't want to plug an analog or digital optical audio cable into my MBA as that defeats the purpose of using HDMI (i.e. a single connection) to my receiver (which then passes just the video through to my TV). I had to use an analog cable with my MBP in order to get stereo out of it on my old speaker system and I refuse to do that here.

 

In VLC, start a movie with a DTS or DD track. Open audio -> audio device. What is listed there?

 

There are three listed:
Built-in
HDMI
HDMI (Encoded Output)

Right now I get surround sound from HDMI or HDMI encoded output. That is fine when I am playing back videos but I want to force my Mac to output only 2.0 audio in everything else when VLC is not open (instead of outputting a 5.1 PCM track always with only the front left and right speakers being active).

 

I definitely see the problem. I'm not sure. I'll think about it.

 

I took it down to my Apple Store yesterday and they had no clue either. They offered to exchange it for a new one but I didn't want to go through that (plus there is an Invisishield and a few stickers on my MBA already). The guy at the Genius bar essentially said that I can't change the output settings for audio over the Thunderbolt/mini-DP output. The Mac will automatically determine the audio that my receiver can accept and that is it.

Strangely enough, I hooked it all back up this morning and, even after restarting my MBA a few times, it is now outputting 2.0 audio to my receiver and then I can select encoded output in QuickTime, VLC, or iTunes and get 5.1 audio. So now it is back working the way I want it. I don't know what happened between there and here but it managed to do something. Hopefully it sticks.

 

so your receiver will can apply dolby plii, cool

 

Yeah, it can do that only when receiving stereo audio. I am not sure what was happening as my MBA was constantly sending a 5.1 PCM signal even when no audio was playing at all. It didn't do that initially but, after the 3rd or 4th day of owning it, I noticed that my receiver was getting a full, silent 5.1 PCM signal. It just sucked as I like using Dolby Prologic II for stereo sources (i.e. Hulu) for movies and TV shows while I think Neo:6 for music does a pretty good job. Much better than having audio come only from the front left and right speakers (no subwoofer either).

 

That's interesting. My receiver will take a stereo signal and send the low frequencies to the subwoofer. other than that I sometimes use 6 channel dolby audio, but I'm not much interested in upconverting 2 channel audio to 6 channels. kind of ruins the artistic choice in my opinion.

I wouldn't mind listening to 5.1 music mixed for 5.1 though