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I guess it depends on the providers. I capture Star Trek: TNG on my
replaytv (2200 kbps video 192k mpeg-2 audio) and the pro-logic survives
just fine for playback. I am new to myth, have played with WinPVR 250,
350 and 150 cards and the encoding they do is better than that of the
replaytv so there is no reason from a hardware standpoint that the
dolby pro-logic encoding should be lost.<br>
<br>
W<br>
<br>
Jeff Clemens wrote:
<blockquote
cite="mid8f2019aa0603150741t4f176a16r8527fd0fe6a42168@mail.gmail.com"
type="cite">
<div>Prologic (the original) is basic stereo sound with the rear
channel encoded in both left and right out of phase with each other,
and the center channel encoded in both left and right in phase. The
prologic decoder in your reciever then sends L+R to the center channel,
and L-R to the surround channel. It also has some more advanced logic
to try to remove true L and R channel information from the front and
rear speakers, but its not inherently encoded. In any case, its a far
from perfect encoding scheme, but does allow the TV tuner card to
capture the encoding without having to do anything special (all it does
is record the L and R signals). </div>
<div> </div>
<div>That said, the redundant information necessary to allow prologic
to work may not make it through the compression process, its hard to
say. Generally, the human ear/brain system does not process phase very
well, so phase information may be dropped in the compression as
irrelevent (depending on the compression level and type used by your
tuner card). Analog TV may or may not be encoded in prologic (that
depends on the broadcaster). If it is, it would still not be
comparable in audio quality to Dolby Digital or DTS, which both use
independently recorded and compressed channels for each of the 6
channels of audio. If you are comparing analog TV audio with a DVD or
something, there's no comparison. However, even with poorly encoded,
compressed and decompressed prologic, you should get some improvement
over straight stereo. Try switching back and forth between stereo and
prologic modes on your reciever while watching analog TV and see if you
notice a difference. </div>
<div> </div>
<div>I've noticed with my local broadcasters, and some national cable
channels, that the stereo image seems to be pretty narrow. In other
words, almost all signal is recorded in both the left and right
channels, in phase. Thus, when I have stereo on, its like running the
same signal through both speakers. When I have Pro-Logic on, almost
the whole signal comes through the center channel, and only background
noises and some music come through the L, R and surround channels.
This is just due to basically un-encoded, or poorly encoded Pro-Logic
on the transmission end, and there's nothing you can really do about
it. </div>
<div> </div>
<div>heh, </div>
<div>Probably way more information than you really wanted,</div>
<div> </div>
<div>Jeff<br>
<br>
</div>
<div><span class="gmail_quote">On 3/15/06, <b
class="gmail_sendername">Bryan Bennetts</b> <<a
href="mailto:bbennetts@blueyonder.co.uk">bbennetts@blueyonder.co.uk</a>>
wrote:</span>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">Hi
all,<br>
<br>
I know there's been loads of posts on s/pdif & 5.1 topics, but I've
been<br>
bashing my head against this for quite a while and still am stuck :-(
<br>
<br>
I'm using the s/pdif output on my VIA 82xx sound card with success when<br>
playing DVDs in myth-dvd, all my speakers produce sound and everything
is<br>
hunkydory.<br>
<br>
However, when watching live tv I'm only getting the front L & R
speaker
<br>
producing (not very good) sound. I was expecting all the speakers to
emit<br>
sound in a dolby prologic stylee, or am I mad?<br>
<br>
I have AC3 pass through set in both my Xine config and mythtv settings.<br>
<br>
Here's the relevant (?) snippets from my .asoundrc :
<br>
<br>
pcm.!default {<br>
type plug<br>
## Uncomment the following to use mixed analog by default<br>
# slave.pcm "dmix-analog"<br>
## Uncomment the following to use unmixed digital by default<br>
slave.pcm "digital-hw"
<br>
## Uncomment the following to use mixed digital by default<br>
# slave.pcm "dmix-digital"<br>
}<br>
<br>
pcm.digital-hw {<br>
type hw<br>
card 0<br>
device 1<br>
}<br>
<br>
# Control device (mixer, etc.)<br>
ctl.digital-hw {<br>
type hw<br>
card 0<br>
}<br>
<br>
Any guidance or pointers to relevant threads/docs would be greatly<br>
appreciated.<br>
<br>
Cheers, Bryan.<br>
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</blockquote>
</div>
<br>
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