[mythtv-users] 7+1 audio with alsa, xine and 5+1 DVDs

Franco mythtv at email.it
Sun Jun 5 22:19:55 UTC 2005

Hi Mike,

thank you for the detailed explaination.

> I'm understanding this to mean you're going directly from the sound card 
> to the speakers with no A/V receiver in between.

Ehmm... yes, they are active speakers sfecifically designed
for that soundcard. There is a remote controlled amplifier embedded 
in the subwoofer and seven cables going from it to the speakers.
I understood your point in leaving 5.1 as is (thank you again for the
explaination), however, experimenting may be fun:

> You could "easily"* do this using ALSA's .asoundrc to specify a device 
> [..]
> set up xine to use this ALSA device for 5.1 soundtracks.

I'll try again to study alsa documentation (thank you for the link).
Actually all my previous attempts failed and I was hoping somebody
would give me some code to copy & paste ;-)

> requirements for THX certification.

Actually, I've spent lot of time on THX too.
My soundcard and speakers are both THX certified (I discovered them
following the links on THX site). There is an hardware upmix function
on the amplifier (5.1 to 7.1 and 6.1 to 7.1) as well a software
upmix funcion (only available with the provided windoze software).
As this equipment (hw + sw) is THX certified and published on THX site,
it doesn't seem that upmixing isn't compatible with THX quality...

As to the requirements for THX certification, I've asked them a lot
but what I got is: nothing. It seems the specifications are top secret,
that is, are not open.  Unless something has changed in the while,
they won't tell you. If you want to build a THX compliant room, you must 
pay them and have their technicians come to you, check your room
and tell you what you have to do without releasing the specs.

Back to the initial point, I _can_ operate the hardware THX-certified
5.1 -> 7.1 upmix, but as long as I "zap" between Myth menus, I have
to continuously walk around the room, check if some speaker is not
working, and operate the upmix accordingly... not very user-friendly
hence I am the only person in my house able to operate the system...
would be better if it happened automatically.

Also, another point: the volume level in the room changes a lot
depending on the number of speakers that are working.
i.e. if only 2 speakers are woring you raise the volume quite a lot.
Then you switch to something using 7 speakers and suddenly your
ears get hurt by a too high volume in the room... you should always
be able to predict when this happens and lower the volume before
changing Myth function... again, not very user friendly.
If all the speakers are always working, you set the volume just once
and then you can switch between myth menus without fear... :-)


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