Re: Questions about MCE TV
From: George Economos (nospam_at_hatespammers.com)
Date: 04/14/04
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Date: Wed, 14 Apr 2004 15:54:13 -0400
Thanks for taking the time for such an informative reply. Great post!
george economos
"Luis A. Burgos" <luis@hasnopublicaddress.com> wrote in message
news:%232A%23VTlIEHA.2744@TK2MSFTNGP10.phx.gbl...
> Hi George,
>
> In my experience, the TV quality is not like live TV regardless of the
Video
> card you are using. It seems that some cards do a better job than others
> with s-Video and Composite, but at the end, the quality is definitely
> inferior to real "live" TV.
>
> TV quality improved from MCE v1.0 to 2004, so if the trend continues -and
I
> don't see why not- we should expect better TV quality in future versions
of
> MC.
>
> The TV quality depends on many things: quality of the signal feed, quality
> of the hardware of the TV PVR/tuner, the TV tuner driver, the settings of
> the MPEG-2 encoder built into the PVR, the mpeg-2 decoder, -notice that
live
> TV is not actually "live", but about 2 sec offset- the video card
components
> and driver. When you go through composite, or even s-video, there're still
> more signal manipulation where information is lost.
>
> Notice that there's nothing in MC itself that affects the quality of TV,
> it's mostly third party components. The PVR tuners that MCE uses are
> typically in the low-end of the spectrum, so certain degradation of
quality
> is expected.
>
> So to answer your questions:
>
> Question #1: What components in MCE are responsible for displaying TV?
>
> Answer:
>
> 1.-The signal comes from you cable provider, antenna or STB. If the signal
> comes from antenna or analog CATV, then it goes through the TV tuner who
is
> responsible tuning in the channel you selected and extract the video and
> audio component from the carrier and recover the NTSC compatible
> video/audio signal from. If the feed comes from a STB in the form of
> composite or s-video, then the previous step does not exists, instead, the
> analog signal comes from the cable box in either composite or s-video
format
> and goes straight to the PVR. (step 2)
>
> 2.-Once you have an A/V signal, it goes then through the PVR, which
> compresses the signal on the fly using the MPEG-2 compression algorithm.
The
> MPEG-2 algorithm is what's called a "lossy" compression, that ism in order
> to achieve a high compression ratio, it gets rid of the "details" that
"are
> not important" and "no one will notice". Then it writes this stream to
> disk.
>
> 3.- If you are watching live TV, then what MCE does is start reading from
> the file the PVR is writing to, just a little bit after the current
position
> (that's why there is a 1~ 2 second delay between "real" live TV and MC
live
> TV) This allows you to pause live TV, rewind and FFWD, because you are
> actually reading from a buffer, and not displaying the actual signal that
> comes from the cable. You may argue that DVDs are also encoded in MPEG 2
and
> they look great, and that's true, but, the MPEG-2 encoders in the PVR
> systems available in MC are -my guess- single pass, probably constant bit
> rate, one size fits all, encoder.That means that they use settings that
work
> well "most of the time". On the other hand, DVD are professionally
encoded,
> with real people with very deep understanding of the encoding process,
> adjusting the settings for each scene, to achieve the best results, as you
> may have guess, the different in price is as big as the difference in
> quality, and they do not compress the image while they are filming, like
the
> PVR does, but after. One of the big challenges of MPEG encoding are dark
and
> fast-movement scenes, however, the settings in the PVR are adjusted to
work
> well for average conditions
>
> 4.- To display this image, MC needs to decode the information it's reading
> from the file the PVR is creating, which is compressed in MPEG-2 format.
To
> do that, it uses whatever MPEG-2 decoder you have in your system -WinDVD,
> Power DVD, nVidia, etc, which recreates, based on the algorithm
> implementation, its interpretation of the original content. Not all MPEG-2
> decoders are created equal, and some do a more better job than others in
> recreating the original colors and contrast.
>
>
> 5.- To display the "interpreted" content, MC needs to render it on the
> computer screen or monitor and does that using the VGA adapter in your
> system. Since the minimum VGA resolution is 640 x 480 and the NTSC screen
> only has 425 visible lines, the VGA needs to convert the signal so it
"fits"
> on TV. Some information is also lost in this process, that's why your
> desktop looks crappy on TV. Additionally, if you are going out through
> Composite or s-video, the video card needs to convert the digital
> information it has about the video to an analog format, so your TV can
> display it. There's also slight degradation during this process due to
> bandwidth limitations.
>
> This is how the image from your CATV is displayed in your computer screen
> using MC, as you can see, of all the components involved in displaying the
> image, the only component that is not liable at all for the signal quality
> is MC itself.
>
> Question #2: will trying different decoders effect the quality of the
> picture?
>
> The answer is yes, up to a certain extent. Different decoders will produce
> different video quality, but never better than what was originally
recorded,
> and the quality of the recording depends on the settings and hardware of
the
> encoder (hardware does N/A for software encoders like ATI), but can never
be
> better than the analog signal received, and the quality of the analog
signal
> depends on the Tuner quality and that goes up the chain up until the TV
> studio.
>
>
> Question #3: Are there any tweak apps I can use to adjust the picture
> quality from my AIW 9800 to my television?
>
> Each video card provides a front end that allows the user to adjust
certain
> variables that affect the perceived quality of the image, such as
> saturation, tint, contrast, sharpness, etc. You can change those settings,
> as well as your TV settings to your heart's content, but in my experience,
> you'll never going to get the same quality as you get on a TV screen.
There
> are probably hacks out there to tweak with parameters the video card
> manufacturers don't want you to mess with, but I doubt it will improve the
> quality much more than what you are able to do with the available tools.
>
> Hope this helps you understand everything that's involved in the "live" TV
> process of MC. I have tried to be not too technical, and it may offend
some
> highly technical people. I may have also made some mistakes as I have not
> worked directly with any of this technologies directly for quite a few
years
> already, is this is the case, please do not hesitate in pointing it out.
The
> last thing I want is to leave people with the wrong understanding out
there.
>
> Your post was good and you seem to be very well informed. Now pardon me
for
> the long answer....
>
> See you next time.
>
> regards,
>
> Luis
>
>
> "George Economos" <nospam@hatespammers.com> wrote in message
> news:O54sEqiIEHA.2244@TK2MSFTNGP09.phx.gbl...
> > Okay to start I am one of those suckers that managed to get his AIW 9800
> > working with MCE :)
> >
> > I split my cable sending one signal to my STB and the other to my AIW
> 9800.
> > Both are hooked up to my Yamaha A/V receiver using a composite RCA
> > connection.
> >
> > That being said the picture quality while watching TV from the MCE
leaves
> a
> > lot to be desired. The colors seem to be washed out and not as vibrant
> when
> > compared to the output of my STB. ( From what I understand I should
> expect
> > this )
> >
> > Now some questions:
> >
> > (1) What components in MCE are responsible for displaying TV?
> >
> > If understand it correctly the encoder (ATIMCE) captures the tv stream
and
> > encodes it into mpeg-2. Next the DVD decoder is used to decode and
display
> > the TV picture.
> >
> > (2) If this is correct will trying different decoders effect the quality
> of
> > the picture?
> >
> > BTW - I thought I was using the ATI decoder but after I executed the
> command
> > DVDUPGRD /detect it showed I was using Cyberlink's decoder. ( I don't
> > remember installing PowerDVD nor does it show up in Add/Remove
Programs ).
> > I still need to run GraphEdit to be sure but cannot do so since I use
> Remote
> > Desktop and UltraVNC to administrate MCE box.
> >
> > (3) Are there any tweak apps I can use to adjust the picture quality
from
> my
> > AIW 9800 to my television? The ATI control panel has a setting for
> adjusting
> > the contrast and color saturation for the tv, these are already set to
> there
> > maximum values.
> >
> > Sorry for the long winded post. Awaiting some great advice.
> >
> > George Economos
> >
> >
> >
>
>
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