[mythtv] [mythtv-commits] Ticket #1104: multi channelaudio support

[Lueddich at gmx.de]

I'm using a ASUS Pundit-R with an integrated ATI IXP Sound Device, I think, it's a 150...


-------- Original-Nachricht --------
Datum: Wed, 16 Aug 2006 18:19:06 -0400
Von: "Michael T. Dean" <mtdean at thirdcontact.com>
An: Development of mythtv <mythtv-dev at mythtv.org>
Betreff: Re: [mythtv] [mythtv-commits]	Ticket	#1104:	multi	channelaudio	support

> On 08/16/2006 03:33 PM, Jan Kleinig wrote:
> 
> > Hi,
> >
> > I have the same effect with AC3 using ALSA:surround51 :( But using 
> > this device, I have even no sound playing a non-AC3-recording :(
> 
> 
> Right.  That was the, "For now," in the request.  :)  BTW, which sound 
> card are you using?
> 
> Mike
> 
> >
> > Michael T. Dean schrieb:
> >
> >>On 08/15/2006 12:33 AM, Mark Spieth wrote:
> >>
> >>  
> >>
> >>>>Analog and ac3, don't know about german channels providing dts ;)
> >>>>   
> >>>>
> >>>>      
> >>>>
> >>>the 6 analog channels out (for me) are
> >>>L,R        -> audio out plug 1
> >>>C,LFE    -> plug 2
> >>>SR,SL    -> plug 3
> >>>
> >>>afaict this is standard.
> >>>will do some testing over the weekend or earlier if I have time with my
> >>>limited setup.
> >>>
> >>>does your channel have 6ch audio? (including LFE/subwoofer)
> >>>can you get the startup part of the frontend log to see what the audio
> part 
> >>>is doing.
> >>>
> >>>    
> >>>
> >>
> >>The "standard" in ALSA is described in the comments in 
> >>/usr/share/alsa/pcm/surround*.conf .  The standard for 7.1 audio is:
> >>
> >>#  Hardware output from 7.1 speakers
> >>#  Samples must be positioned:
> >>#    chn0 - front left
> >>#    chn1 - front right
> >>#    chn2 - rear left
> >>#    chn3 - rear right
> >>#    chn4 - center
> >>#    chn5 - lfe
> >>#    chn6 - side left
> >>#    chn7 - side right
> >>
> >>And 5.1 is the same but without channels 6 and 7.  (Channels 6 and 7 are
> >>incorrectly labeled 7 and 8 in the comment.)
> >>
> >>However, some hardware doesn't use this standard.  For that hardware, 
> >>different configurations are specified using a translation table 
> >>(ttable) in the "standard" surround device aliases (i.e. surround40, 
> >>surround51, surround71, etc.) in /usr/share/alsa/cards/*.conf .  
> >>Therefore if using non-standard hardware /AND/ using an ALSA built-in 
> >>device alias, your non-standard hardware will react as would standard 
> >>hardware.
> >>
> >>Specifically, the ICE1724, ICH, ICH4, NFORCE, and VIA8237 all use 
> >>non-standard channel-output mapping for surround.  (So, Mark, if your 
> >>"standard" is based off one of these cards hardware usages, it's not the
> >>real standard.)
> >>
> >>Anyone using a custom definition for his/her audio could add a 
> >>translation table to the custom device alias in /etc/asound.conf or 
> >>~/.asoundrc.  Asking the users to learn enough about ALSA to do so may 
> >>be more than we should expect, though.  (See 
> >>http://www.gossamer-threads.com/lists/mythtv/users/134552#134552 for 
> >>more on ttable.)  Unfortunately, that means the only way to know for 
> >>sure which mapping the hardware uses is to parse the 
> >>/usr/share/alsa/cards/*.conf files, but the only way to know if we 
> >>should use the hardware mapping (instead of ALSA default) is to also 
> >>parse the /etc/asound.conf or ~/.asoundrc and to find out whether the 
> >>device alias specified to Myth is an ALSA built-in or a redefined custom
> >>version of the ALSA built-in or a custom alias that slaves to one of the
> >>ALSA built-ins or a custom alias that provides its own translation 
> >>table.  Obviously, none of this should be done by Myth...
> >>
> >>For now, Jan, what happens when you change your MythTV audio output 
> >>device to "ALSA:surround51"?  With that, you'll be using an ALSA 
> >>built-in alias, so you'll get the ALSA-standard mapping, so if Mark used
> >>the ALSA standard for the patch, you should get proper output to the 
> >>proper speakers (assuming your speakers are connected to the correct 
> >>outputs ;).
> >>
> >>Mike
> >>_______________________________________________
> >>mythtv-dev mailing list
> >>mythtv-dev at mythtv.org
> >>http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-dev
> >>
> >>
> >>  
> >>
> >------------------------------------------------------------------------
> >
> >_______________________________________________
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> >mythtv-dev at mythtv.org
> >http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-dev
> >  
> >
> 
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