Macbook USB Audio 5.1 Output

Discussion in 'Apple TV and Home Theater' started by SparkyMarky84, Jan 19, 2009.

  1. SparkyMarky84 macrumors newbie

    Jan 13, 2009
    Hey guys,

    ok i have another audio question for you. I have a Dolby Decoder with coax-in. Basically i want something to connect my macbook to this. However i have read that the optical out on the macbook is only suitable for DVD playback. Basically i want something which will allow me to output 5.1 sound from DVDs, games, divx movie files, and iTunes etc via a Coax connection which i can connect to my decoder.

    I have seen a lot of generic usb audio cards which have optical and coax outputs and claim "Dolby Digital output", however does this just mean they will output 5.1 audio from a DVD (just like the Macbooks build in card) or will it decode/output all audio in 5.1 format via the coax connection.

    If anyone has any suggestions as to a product which would do this then i would be most greatful.

    I'm just looking to connect my macbook to my decoder to play music in surround sound and watch the odd dvix/xvid movie in surround, i'm not looking for a megabucks professional solution or anything.

    Thanks guys,

  2. Alrescha macrumors 68020

    Jan 1, 2008
    It is my experience that an external device behaves the same as the built-in optical out. Either one will send PCM audio to your decoder (you need an optical to coaxial converter if you use the built-in interface) and DVD Player, VLC, and EyeTV can all be told to output encoded audio. System sounds and alerts can be directed out of this port as PCM audio.

    One problem is that it doesn't share nicely. If DVD Player is sending Dolby Digital to the interface, nothing else can generate sound. Worse, whatever *tried* to generate sound is probably broken, in that it will never play sound again until it's restarted. Sometimes not until the system is restarted. To the best of my ability to tell this is an Apple problem.

    I've tried to work around the sharing problem by getting a USB device and using it for encoded output and leaving the internal port as plain old analog audio. This works better, but applications using a dedicated external interface still have trouble controlling it: DVD player will become unresponsive if you scrub around in a movie, EyeTV will hang when a program reaches the end, etc. None of this seems to happen when using analog output. I suspect this is also an Apple problem but to be fair I have not eliminated the external interface as a possible cause.

    So, for occasional use it all does work but it's fragile. Trying to use it on a daily basis is frustrating. I have an Apple TV, so if I want to do something with 5.1 I'll probably use that instead. Good luck!

  3. drichards macrumors 6502a


    Nov 30, 2008
    Why bother with the usb sound? I'd use a optical to digital coax convertor box, they're tiny cheap and reliable. Check Amazon and monoprice.
  4. SparkyMarky84 thread starter macrumors newbie

    Jan 13, 2009
    Hi guys, thanks for the replies.

    The reason i dont want to just use a optical to digital coax convertor box is because that will only output 5.1 sound from DVDs and 2 channel stereo for things like games. I want a solution which will send all formats of 5.1 to the decoder, like non dolby digital games.

    e.g. If i used something like the Griffin Firewave then i would have 5.1 output from DVDs, but also 5.1 output from games and other audio sources. However this is not suitable as the Firewave only has analogue outputs.

    Thanks guys, any help is much appreciated.

  5. Alrescha macrumors 68020

    Jan 1, 2008

    I'm not sure I understand. The optical port (built-in or USB) is transparent to any application that knows how to use it. If you have a game that actually creates 5.1 audio and knows how to transmit encoded audio (like DVD Player or VLC), then the built in port will work.

    I'm not a gamer, I have no idea if such things actually exist. If the game doesn't really generate 5.1 audio, then you are talking about something that generates some pretend 5.1-like sound. That's probably best done in your AV receiver or whatever is getting this digital signal.


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