[mythtv-users] additional configuration items for new sound system in 0.24

Brian J. Murrell brian at interlinx.bc.ca
Tue Nov 16 13:00:29 UTC 2010


Having played a bit with the new sound system in 0.24, I have to say, I
like it's direction.  I find that there could be more options though.

Recently I reported a bug about AC3 stereo not being passed through to
the receiver.  I reported it because I thought it was a bug, but that's
not to say I didn't like the behaviour.  I do prefer to have AC3 decoded
by Myth because my receiver has some latency (and a click) between when
it starts getting an AC3 track and when it starts decoding/playing it.

So it seems that what I would want to do is disable DD and DTS in my
Myth config and enable LPCM, which I am guessing indicates to myth that
I want it to do the AC3 decoding.  That's fine, except that the
connection between my TV and my receiver is optical (and my FE->TV is
HDMI) and so not capable of carrying 5.1 on LPCM (as far as I
understand), but only 2.0.

So what I would like to tell Myth is, that if the sound is AC3 and it's
2ch (or less), decode it and send it over LPCM, but if it's more than
2ch and it's DD or DTS then pass it through to the receiver for
decoding.

In order to achieve that it seems that I need an option box to tell Myth
to prefer decoding AC3 itself when possible and I also need an input box
to tell Myth how many channels it can use LPCM to send to the reciever. 

With regard to this latter option though, perhaps many people don't
understand the abilities of HDMI vs. toslink so perhaps rather than a
more technical option like specifying how many channels can be carried
to the receiver a more simple/consumer-like option to specify whether
your receiver is connected via optical cable or HDMI should be provided
and from that, Myth determines how many channels it can send with LPCM.

Thots?

b.

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