[mythtv-users] digital sound in parallel to receiver and TV

Terjesen Jens Peder Jens.Peder.Terjesen at devoteam.com
Fri Dec 18 10:46:39 UTC 2009

Allen Edwards wrote:

On Thu, Dec 17, 2009 at 12:58 PM, Bert Haverkamp <bert at bertenselena.net> wrote:

Hello all,

I'm having difficultly setting up audio out to my liking. I'm mailing
here in the hopes that someone has figured this out:
I'd like to setup similtaneous sound to :
1) my TV via hdmi
2) my receiver via spdiff
I want both the TV and the receiver to output the sound and chose
between the two depending on my needs. (my wife doesn't bother turning
on the receiver and listens only via the TV mostly.)

However, my TV doesn't handle Dolby, AC3, but my receiver can.
If I use passthrough the TV outputs horrible noise.
If I dissable passthrough I miss the ability to listen to 5.1 in films.

I would like to be able to send stereo via hdmi and simultaneously
passthrough via spdiff.

I've been playing with asound.conf. I can send stereo to both in
parallel, but for 5.1 is still the issue.
Does anyone have a solution here?



I find it difficult to believe that your TV cannot decode the digital signal that comes off the TV signal.  Even if the TV cannot play 5.1, it should be able to pull the stereo out of the 5.1 digital stream.  It is, afterall, doing just that when you listen to an OTA station.

What I do is send spdif streams to both my surround system (4.1) and to a decoder feeding stereo to the TV.  

However, I suspect you will have difficulty getting both HDMI audio and spdif out of the myth box.  But I would bet you can get two spdif outputs and that your TV can take one of them and your surround system the other.  All Asus MBs have internal spdif outputs that only require a simple passive converter, for example.

That said, I wrote down everything else I know about it here:

Please let me  know what you find out and if there is anything else I can do to help.


I think he has digital sound via both HDMI and SPDIF working at the same time. It certainly works for me with an ASUS MB.

I have optical SPDIF straight from the MB and use a passthrough cable from the internal SPDIF header on the MB to my Nvidia 9500GT card.

The problem he is describing is the same I see with my setup. With DD/DTS passthrough enabled and a recording containing DD/DTS sound the compressed digital signal is sent unaltered to my TV which decodes it as a stereo signal and only outputs white noise.

What I think he is asking for is if there is a way to get the DD/DTS downconverted to stereo through HDMI while still keeping it unaltered via SPDIF. And if he has the same setup as I have the answer is no. That is because it is the exact same signal in both HDMI and SPDIF. The signals comes from the same audio chip which just feeds it to the optical SPDIF and the SPDIF header on the MB at the same time.


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