[mythtv-users] More Digital Audio Q's

[Steve Adeff]

On Sunday 27 November 2005 16:26, Michael T. Dean wrote:
> Steve Adeff wrote:
> >On Sunday 27 November 2005 14:19, Brian Foddy wrote:
> >
> >
> >If you require bit-perfect SPDIF output (DVD's 5.1 HDTV) get a Chaintech
> >AV710, they can be had for $25 from newegg
> >http://www.newegg.com/Product/Product.asp?Item=N82E16829120103
> >it does true 192/24 (which NONE of the Creative chips do) and does true
> >bit-perfect optical digital output.
> >Heres a thread about using it in linux:
> >http://mysettopbox.tv/phpBB2/viewtopic.php?t=4132&
> >
> >really, any of the ENVY24HT based cards are what you want for bit-perfect,
> >there are a few out there, with varying levels of SPDIF support (in/out,
> >optical/coax) and with DAC of varying levels of quality. Google is your
> >friend in this regard.
>
> What exactly does this mean?  If you're doing AC-3 passthrough from
> Myth, won't the S/PDIF output be as bit-perfect as was sent to you by
> the digital TV broadcaster/DVD production house?  Or, are you saying
> that some sound card's mangle the stream they're attempting to pass
> through?
>
> Mike

Yes, 'mangle', because the chipset will do freq/bitrate conversion if needed 
to match the abilities of the output circuitry. If the output circuits can 
handle 24/196 then no change is needed and the chip just sends out the 
signal. Creative's output circuits can't handle 24/196 so the signal gets 
reprocessed to match its output (20/92 iirc). This is whether the signal is 
DD/DTS or PCM.

-- 
Steve