Re: 5.1 interfaces.
Re: 5.1 interfaces.
- Subject: Re: 5.1 interfaces.
- From: Mark Cookson <email@hidden>
- Date: Fri, 11 Oct 2002 20:11:38 -0700
On Friday, October 11, 2002, at 04:42 PM, Brian Willoughby wrote:
I just heard about the M-Audio Sonica, but there doesn't seem to be
enough
in-depth information on their site or in their press release. Does
this device
*create* an AC-3 stream from 6 discrete PCM channels sent to
CoreAudio? ...
or does it merely pass through an AC-3 stream that already exists -
e.g. from a
DVD soundtrack file?
It doesn't encode the streams. It just sets the S/P-DIF data flag
(which it seems that 99.9% of decoders don't need to have set to notice
and decode AC-3) to allow you to select and output AC-3 audio.
The Sonica also claims to "support" DTS, but I could not determine
whether it
will create / encode DTS or merely pass it through like a consumer DVD
player
with DTS support.
It just passes them through. Since DTS is an encode-only format
(doesn't require the data flag set in the S/P-DIF stream), anything
that can transmit 16-bit stereo PCM audio without corrupting the stream
will support DTS. I think that the AppleUSBAudio driver does the
float->int conversion correctly and therefore doesn't corrupt the data
running through it. It's the outboard decoder that has to notice that
it's a DTS stream and do the right thing. Assuming that you don't
mangle stream, this is a no-brainer.
--
Mark Cookson
Engineering Droid
Apple Computer, Inc.
Core Audio CPU Software
6 Infinite Loop MS 306-2CW
Cupertino, CA 95014
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