TV signal is poor quality when connecting STB box to TV card via S-VIDEO

pjuegos · 27-03-2009 05:03PM #1

Hi everybody,

I got my media center setup but I have a problem with the TV picture quality.

I have a TV card installed in the PC "Hauppauge WinTV HVR-1300", which is connected to a STB box through S-VIDEO. The signal is displayed in TV using WinTV no problem. However, the quality is not great because the TV card is compressing the signal using the MPEG codec.

Is there any way to tell a TV card to not compress the signal when watching TV? The idea would be watching raw video in real time and just compressing the signal to record TV (when is needed). Does anybody know how to do that?
Also, do to the time it takes to do the compression in real time, the card is not very responsive for changing channels. I hope to sort out this problem if the received signal is not compressed.

Help would be much appreciated

Thanks

bazwaldo · 27-03-2009 05:14PM

The s-video signal is analgue. It would need to be digitised to make the pause, rewind, ffwding available in a media center. If the picture is that bad, it sounds like something else is up. Usually its the mpeg2 decoder or the gfx card settings.

pjuegos · 27-03-2009 06:04PM

Hi bazwaldo,

thanks for your reply.

Even though s-video is analogue, it does not stop me from pausing, etc... Using the" pause" operation as an example: the "pause" is done in the STB box by using an IR blaster. Thus, each time that i want 2 pause (for example), the PC sends a command to the STB box which will pause and the media center will just receive the analogue SVIDEO input that was paused in the STB box.
So, I dont want the media center to do anything except displaying the raw analogue signal when watching TV and using MPEG2 for recording TV.

The image is not extremely bad. It is just worse than just connecting the STB box to the TV. What I want to do is just telling the TV card not to compress the signal when watching TV.

Thanks

bazwaldo · 27-03-2009 11:09PM

pjuegos wrote: »

Hi bazwaldo,

Thus, each time that i want 2 pause (for example), the PC sends a command to the STB box which will pause and the media center will just receive the analogue SVIDEO input that was paused in the STB box.

What STB is it? sky+? I'm confused. If your stb can pause, why do you need a media center for TV?

pjuegos · 28-03-2009 01:27AM

sorry, sorry!!!!

I installed yesterday the PC media center and I think i got overexcited....

I was thinking of changing the channel through IR blaster and I picked up a bad example "pausing" without thinking what that actually does...

No, of course I cannot pause with my STB box (NTL). Honesly, I am not too interested in pausing,rewind etc.. My main prioriites are:
watching raw
recording compressed video

Sorry for the confusion!!!!

bazwaldo · 30-03-2009 12:55PM

This is my understanding, I could be wrong.

NTL has its channels encoded using mpeg2. The NTL box decodes it and outputs an analogue signal on the SCART(composite + RGB).

Your TV card encodes the analogue composite input to mpeg2. Your PC outputs the encoded mpeg2 to screen via whatever way its connected to your display be it analogue or digital. The PC needs the video in a digital format to do read it. There is no such thing as analogue to your PC. So when you say raw, its analogue. The card does not compress it exactly. It encodes it into mpeg2 so that the PC was work with it. What you need is to bypass the NTL box and get your TV card to decode the mpeg2 NTL signal. I think this can be done using one of the cam cards which take your NTL card. I've never tried this or read how its done.

pjuegos · 31-03-2009 04:25PM

You might be right I think

MPEG-2 encoding does not have the problem of the quality loss. At the end of the day, DVDs uses MPEG-2 and the quality is great.

However, something in the PC way is introducing distortion and loss of quality to the signal. Could it be that doing an additional MPEG2 convertion in the PC card is affecting the picture quality? Could it be the built in MPEG-2 encoder of the TV card? Is it possible to change the MPEG-2 encoder?

cheers

bazwaldo · 01-04-2009 03:03PM

It encodes using the card (hardware) so it cannot be changed. If your graphics card supports DXVA then the card is doing a lot of the decoding and deinterlacing. I have found that this is usually the source of bad TV playback.

What are the quality issues you are seeing? Can you give more info on your setup (s/w + h/w)?

pjuegos · 01-04-2009 10:48PM

Thanks for willing to help

The HTPC set up is the following

The PC TV card is a Hauppauge Wintv PVR-1110
PC motherboard: Gigabyte GA-EG41MF-S2H
Processor: Intel’s Core 2 Duo E6400

RAM : 1Gb. Another 3GB are on the way...
Graphics card: on-board

Display: Samsung 32'' LCD TV

The stb box is connected to the TV card via S-VIDEO. The image is watchable but it is not great. The loss compared to connecting the STB box directly to the LCD screen is clear

The image is quite blurry, you can really notice it with still text.
Bad image contrast
There are also parallel lines in the screen, like if there was an interference...

Another problem that the card is introducing is a delay in changing the channels. The MPEG2 convertion in the TV card takes time, which is not noticed when wathing a continous stream but is noticeable when changing channels

My idea was using the PC as the only TV input source but I don t think I will if I dont improve the picture quality.

Thanks again!!!

bazwaldo · 02-04-2009 07:39AM

The picture should not be that bad. Something is not right and its not the process. What OS are you using? Are you viewing using WinTV or can you get Windows Media Center to work (if running Windows)?

FYI, NTL STB does not output s-video. But 2 of the s-video pins are shared with composite video so its actually composite (RCA) thats being used.

How are you connecting the STB to PC exactly? SCART to svideo cable? Could there be any interference creeping in here?

Try changing some gfx settings. I see the gfx chip is Intel GMA X4500. Never heard of it so can't comment on what to change.

pjuegos · 02-04-2009 02:01PM

OS is VISTA
I am using WinTV at the moment but the idea is using WMC once I get delivered the logitech remote with IR blaster.

Connection is SCART to svideo adapter.

I tried changing gfx settings in WinTV but i could not get it right...

Thanks!

bazwaldo · 02-04-2009 02:13PM

Try connecting your cables to the TV instead of your TV card to ensure whats going in is of good quality. And your actual gfx driver should have settings somewhere.

pjuegos · 03-04-2009 01:15PM

i try connecting svideo to the TV but for some reason it did not display anything at all.

I will try again this weekend and I will keep you posted of what happens

Thanks!

pjuegos · 04-04-2009 08:00PM

my Samsung TV does not recognise the SvIDEO input for some unknown reason...

However, I have connect the STB box to the TV card via composite video. The interferences are gone, so they were an svideo issue
The quality of the image is very similar. Probably a little bit better than using svideo, which does not make too much sense since svideo is supposed to provide better picture quality. Still blurry anyway. If you reduce the size of the image it is OK, but when you display the image in full 32" LCD TV screen the loss in quality between connecting the STB to the TV directly and doing it via TV card-composite is quite clear

cheers!!!

bazwaldo · 05-04-2009 07:57PM

NTL box does not output svideo.

What resolution is your tv and whats your htpc res set to?

pjuegos · 06-04-2009 07:58AM

When I say svideo, I mean SCART to svideo cable.

the TV is an LCD TV Samsung LE32R8
The max resolution for HDMI input is 1024x768
The max resolution for VGA input is 1360x768

Unrelated topic, don't reply if it is a diversion from the thread topic
Now that you mention resolutions, when using HDMI input each time that I launch WMC there is a resolution change in the TV. I cannot find any way to stop that to happen. The interesting thing is that it does not happen with VGA.

Thanks

bazwaldo · 08-04-2009 10:43AM

When Media Center opens, it adjusts the resolution to what is set within it. To get the resolution you want for when MC opens, go throiugh the setup display wizard in MC.

You should try to get your HTPC res to match your TVs resolution so that the upscaling is done by your gfx card. Or if you want to set the resolution to 720x576 interlaced, then your TV will do the upscaling so your gfx card does not. Worth a try to see how your gfx card is compared to your TV for upscaling. BTW, MC will have much less on the screen at such a small res. Still, worth trying once to see the results.

When I say the NTL box does not output svideo, I mean that the scart pins for svideo are not used for svideo. There are 4 pins for svideo. 2 of which are shared with composite and this is what your NTL box is using. So when you used svideo, it actually used 2 pins to transmit composite and it was composite that your TV card encoded. If it used svideo, you would have seen a B&W picture.

pug_ · 10-04-2009 08:33AM

Sorry to jump in on this thread, but I'm having pretty much the same problem.

Maybe it's different I don't know, but for me it's the fact that I can only get composite picture quality from the scart connector. Is there any way of getting s-video quality picture? The raw feed is scrambled, and I've looked but can't find any scart adaptors that will plug directly into a PC.

The only option I've found is scart to s-video, but the picture quality is so poor compared to what I'm used to that I just can't bring myself to watch it.

bazwaldo · 10-04-2009 10:27AM

S-video is not available from an NTL box. Only composite or RGB. There are RGB to svideo converters available (maplins). However if you get a decent scart to composite cable (I got one from ebay for less than a tenner) then the quality should be good. Definitely watchable and bearly a differerence to the RGB direct to the TV.

Before I got the single SCART to composite, I used a SCART adaptor which had 3 female composite outputs and then used male to male composite cables. The picture was still quite good with this too. In fact before that I used an svideo cable and my card was able to take the composite feed from the svideo input and that was decent quality too.

I found that most of the problems I have seen with TV on my HTPC were due to the deinterlacing or resolution. Once I got the right settings, the picture was very good.

Can you explain what problems you are seeing with the picture? Is there interference, smearing, interlaced images, blended frames? Might be able to narrow down the issue from that.

pug_ · 10-04-2009 11:57AM

Maybe I have a different stb or something, I have chorus MMDS where I live, but I don't have any RGB coming out of the back of my box, only 2 scarts, and an option for raw feed in and back out again via coax.

Kinda hard to describe what it is that's wrong with the picture quality really it's perfectly watchable just not as sharp as the feed direct into the telly via scart. It kinda reminds me of a badly recorded video the quality is just lost somewhere. Hmm, trying to think of a way to describe it here, I suppose you could say it looks digitised not that you can see pixles or anything but you'd still know it was going through a computer, similar ish to watching a full screen standard def youtube video.

I'm not sure how to differentiate between smearing, interlaced images, and blended frames they're not terms I'm familiar with sorry, it's possible it's one of those I just don't know. It doesn't look like interference though the picture it's self is perfectly smooth and it's all there all of the time.

I should probably say that I also have just a bog standard crt telly, and avi's play perfectly so at least I know the signal going from the PC to the TV is okay.

bazwaldo · 10-04-2009 01:00PM

RGB is transmitted on the SCART too on the NTL (pace) box. In the settings theres an option to output composite or RGB (if you select RGB, composite is also outputted to the SCART). I can't comment on the chorus MMDS box though.

Sounds like the issue is the decoding and display of the video. Whats you setup? Vista/XP? Using Windows MC? What gfx card?

pjuegos · 10-04-2009 03:04PM

thanks again,

I changed the resolution in WMC and now is fine. The only problem I am having is that i have to do an autoscan in my TV each time that I restart the PC for getting the res right for the windows desktop. I wonder if that can be automated...WMC res is always fine now

I have connected analogue NTL to the TV card/WMC and I have noticed that in WMC the picture does not fit into the screen. Can WMC resize image?

Final question...(bazwaldo, u r a legend giving good answers

)
Sometimes, I get no sound with HDMI and I cannot figure out why... any idea?

Thanks

pug_ · 10-04-2009 03:09PM

Here's where we get to the tricky part. I'm one of those funny folk that doesn't like paying for an operating system (or hardware) so my setup is running Mythbuntu on a low end P4 system.

Graphics card is an Nvidia Gforce4 with 64Meg ram (I know, I know) but it works perfectly for any avi or MKV files I throw at it at much higher definition than I'd expect from the TV output.

I'm using a Hauppage WinTV PVR 500 to take the signal from the stb. I'll admit my knowledge of exactly how the Hauppage card formats the video stream and forwards it to the graphics card is pretty ropey, but from what I've seen nothing is under any kind of stress at any stage so in theoryit should be able to handle it fine... I think

bazwaldo · 10-04-2009 04:33PM

pjuegos wrote: »

The only problem I am having is that i have to do an autoscan in my TV each time that I restart the PC for getting the res right for the windows desktop. I wonder if that can be automated...WMC res is always fine now

You need to scan for TV stations everytime you reboot! That can't be right. Is that what you are saying?

pjuegos wrote: »

I have connected analogue NTL to the TV card/WMC and I have noticed that in WMC the picture does not fit into the screen. Can WMC resize image?

Hit in 'i' or info button on remote. Select zoom. Pick the best one.

pjuegos wrote: »

Sometimes, I get no sound with HDMI and I cannot figure out why... any idea?

No idea on this one. Any pattern to when the sound is there or not?

bazwaldo · 10-04-2009 04:37PM

pug_ wrote: »

I'm one of those funny folk that doesn't like paying for an operating system (or hardware) so my setup is running Mythbuntu on a low end P4 system.

You'd be funny if you did like paying for it

pug_ wrote: »

I'm using a Hauppage WinTV PVR 500 to take the signal from the stb. I'll admit my knowledge of exactly how the Hauppage card formats the video stream and forwards it to the graphics card is pretty ropey, but from what I've seen nothing is under any kind of stress at any stage so in theoryit should be able to handle it fine... I think

I've no experience of Mythbuntu so can't say if your problems are related to that. I would suggest changing any settings related to video or deinterlacing. This worked for me.

pjuegos · 10-04-2009 05:00PM

oh no . What I meant is that each time I reboot the resolution of the desktop does not mach the TV screen and I have to use a function on my samsung TV called "autoscan" that adjusts automatically.
Unfortunatelly, I have to resize the image at each reboot

cheers

bazwaldo · 10-04-2009 06:32PM

I'm still not sure what you mean. The HTPC and TV should have the same resolution for the best results. If your TV needs to do an autoscan to adjust, it suggests that the resolution of your HTPC is not matching the TVs. Try some different resolutions to see what happens.

If your TV is not recognising the HTPC resolution on startup, maybe take a look at your TV manual to see what resolution is best.

pjuegos · 02-05-2009 09:44AM

Hi bazwaldo,

Sorry for the big delay in my response. I am just back to dublin from a business trip...

The best resolution configuration I could get for matching both HTPC and TV is HDMI input is 1024x720. So, I have chosen that resolution in the display settings in Vista and in TV settings in WMC.

However, I still have to readjust at each PC boot the screen size in the TV, which is quite annoying... Interestingly, WMC resolution is fine all the time and does not need to be readjusted...

Thanks

TV signal is poor quality when connecting STB box to TV card via S-VIDEO

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