I'm getting annoyed with the poor quality of the TV-Output built into my mother board (nforce2 chipset, GeForce4 equivalent). Since my first principle of engineering is "it annoyed me, so I fixed it" it seems like time to commit some engineering.

Basically I'm seeing dark, low contrast (either white/light grey/pale colors all look the same or the dark colors do), with distorted colors (either "overexposed" or muddy). I've tweaked and adjusted and fiddled and and tested and compared and ... but the results are always subpar, and it's becoming more and more clear that it's a fundamental hardware issue. From research here and other places I've come to suspect that the problem is substandard output voltages on the svideo connector. I can think of several approaches to try, but before I dump any money into this, it seemed like a good idea to poll the collective wisdom here. The approaches revealed by my researches so far include:

- (Too damned expensive) Use a component amp/receiver. This is supposed to normalize the voltage levels and it makes plenty of sense, but it seems like kiling flies with a 5 pound gold bar. Decent receivers cost as much as my whole MythTV box, and doubling the cost to get an acceptable TV picture seems pretty silly.

- ($185 and lots of work) Switch to a PVR-350 and use it's TV Out which is supposed to be excellent. This means fighting with the pvr 350 output set up, prerelease drivers, sound issues, stability issues, ...

- ($55-$75) Find a video card with better quality svideo driver chips that actually produce good voltage levels. I've heard recommendations for "a cheap GeForce FX 5200 base card" but without specifics (maker, model, chips, ...) that seems like a crap shoot. I'd be slightly concerned with thermal issues in my media machine's already crowded SFF case but not enough to rule it out. Recommendations are requested.

- ($80-$150) Used a VGA/SVGA to TV converter box. I've heard mixed results with these. This one is supposed to be good: http://www.newegg.com/app/ViewProductDesc.asp?description=14-100-010&depa=1 others are supposed to be utterly horrible. Again I'd like to hear recommendations...

Saw another possible option tonight at RadioShack, a distribution amplifier designed to take an svideo or composit feed and pump it up enough to drive 4 TVs. Roughly $40-$45, this assumes that it would normalize the levels...

BTW - If you ARE happy with you video out please leave a note on what you're using...

I'm using nforce2 onboard, and I'm fine with it. I guess I'm just not as picky as some people. Yes it's is ever so slightly more washed out than the same signal plugged directly into the tv, but doesn't bother me that much.

_________________
Have a question search the forum and have a look at the KnoppMythWiki.

Xsecrets

Same as Xsecrets, it does get a bit on the red side at times, but I'm happy with it... Looks almost as good as my 24" Sony.

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cesman

When the source is open, the possibilities are endless!

I think the biggest quality problem with nVidia TV-out is the apparent inability to "pass through" fields from PVR-x50 MPEG2 recordings.

I've read lots of messages and tried various XF86Config settings, but I've never seen one that properly preserves the recorded fields and sends them out on the proper scan line.

You can mask over the problem by deinterlacing, but ideally you wouldn't need to do this.

Sorry that this didn't address the original poster's color quality issues. Radio Shack is pretty liberal with their returns so it might be worth a try to get the $40 box you mentioned. It'd be a shame to spend $100+ for an outbound converter box, especially if there's any chance of your going HDTV in the future... you'll end up spending the same $100+ for a VGA->Component box.

Maybe I'm not describing what I'm seeing right...

I'm not seeing interlace issues, or sharpness issues, or ... what I'm really trying to address here is a color/brightness/contrast issue. It isn't even a subtile issue, to me at least it's glaringly obvious. If there is a character wearing a white shirt and a light grey jacket, the TV tuner shows flesh-white-grey as expected, the svideo TV-out from the box tends to show off white-off white-off white. If I adjust things so that you can see the difference between these colors, darker colors in the shot sink into indistinguishable charcoals and dark browns.

This is especially apparent when watching animation with it's blocks of solid colors (The Simpsons, Futurama, Bebop, Big O, ...), and really annoying when watching live action shows with lots of dark scenes (Farscape, BtVS, Angel, ...). I know this isn't a capture problem because I see the same issues with DVDs too.

What finally pushed me over the edge on this was trying to watch a new DVD (FLCL) which opens with this gorgeous watercolor/pastel style aerial view landscape and seeing a giant bright burned out blur. (BTW - If you like art animation check it out, the story line is not as random as it seems at first glance, the animation style is practically a survey of every technique and style out there (including an homage to South Park), and the backgrounds and characters are often stunning.)

The only (major) dissapointment with MythTV for me has been TV out. As it is the end product of the whole system, that is pretty sad.

I am using a digital Freeview PCI card in the UK, so I have perfect interlaced digital video, recorded to HD as the source. Sony PAL Tv has Composite/svideo/RGB options available through scart.

There are 4 things wrong with TV out.

1) The Output level of the analogue video.
I have used both a GF4 card and a Matrox G400 dual head. Both have low analogue output voltages. When connected to the tv, you should see a total Peak to peak from synch tip to White of 1 Volt. Both of these cards gave somthing like 0.3-0.4 volts. This gives a dark low contrast picture. None of the software contrast/brightness controls fix that, they just let you choose which pixels you want to be Brightest and which one darkest. As the brightest is grey, you can't get a really good picture.

Luckily the Matrox card allows you to tweak the analogue voltage, and wind it back up to a full 1 V P-P signal, for nice bright pictures. The geforce card does not have any software I know of that does this.

tjc The other approach that worked for me was feeding my S-video though my S VHS video recorder, that did the level amplification and clamping very nicely, but obviously it would be better fixed at source, rather than amplifying a low signal.

2) Picture juddering on scroll:
I thought this was interlacing issues to start with but it is not.
What happens is that the frame/field buffer of the TV -out is fed a frame "when the processor has time ) " So although the tv-out will send a field to the TV every 50th second, it might not be the right one.
Turning on the experimental A/V sync helps with this on GF4 cards, and jitter reduction helps on all cards (I think).
This is unfortunatlly missing from any how to: I have read, but really does make a diffrence.

3) Interlacing.
Myth is designed around analogue capture cards, and displaying TV on a PC monitor. It does not do well with interlaced content. It is set up to provide hardware/software de-interlacing, which then feeds a progressive picture to the Graphics card. Normally this goes to the Monitor, but it can also go to the TV out of the graphics card where the Progressive frame is de-interlaced to 2 fields, and interlaced pictures sent to the TV. In the process the original interlacing is completely lost, and you end up with a degraded picture.
Even if you turn of all deinterlacing, the interlaced content is not passed through to the TV properly by GF4. The Matrox card does it under windows and also under DirectFB, but setting up DirectFB is a bit of a drag.

4) RGB is prefferable to Svideo, but RGB is hard to get out of most video cards.

My Matrox card can be set up to give RGB out through a special (home made lead) htis does not work on my main TV, probably a sync on green issue) I t works on my RGB portable.

I have had success with a very simple approach of setting up my GF4 card with the new interlaced output drivers, and then plugging this straight into the TV through the scart socket. [ Dont try this at home unless you know ewhat you are doing !]
The analogue RGB is directly compatible, and all you need to do is recombine the H and V synch. This can be done "properly" but you can get away with a couple of resistors.

I have tried lots of approaches to TV out.

A PC next to the TV, Mythfrontend. Not silent.

i) GF4 - Svideo - dark picture, interlacing artifacts, occassional stutterring on panning shots.
ii) Mattrox G400 - Svideo - Picture bright and clear -, interlacing artifacts, stuttering on panning shots.
iii) Matrox G400 RGB through a self made cable, doesnt work on my target TV (but does on others)
iv) GF4 - simple VGA-RGB scart converter. VGA picture quality, ( occassional interlacing artifacts, occassional stutterring on panning shots)

All of the above have annoying picture flaws, and the quietest PC still makes a lot of noise in a quiet living room. Very low wife acceptance factor.


Video Sender:

Use a vdeo sender to remotely locate the backend/frontend combination from the TV. Pro: Silent, Cons : Microwaving during a movie ruins the picture and all the Picture quality issues of the source TV-Out

Haupauge MVP:

By far the best Video results I have got are by using a Haupauge MVP. It is a simple Stand alone external MPG2 player, with ethernet in, TV out. It is designed to work with a windows server programme, that allows the MVP to network boot, and then select Mpeg files on the servber through a simple graphical interface. There is currently activity to produce Linux software that allows as much as possible of the Mythtv frontend functions to run on the mVP. Currently you can boot from a linux server, and then access the recorded shows off the Mythtv backend, with descriptions. No live tv or any other Mythtv Goodies.

I am currently using this as my frontend. I prefer a totally silent frontend with Good picture quality and V. Limited functions to a fully functional full tower case withe 3 fans and a poor picture.

I have to agree 100% Short of burning a DVD, this is the only way I've played my MythTV recordings via composite or S-video that preserves the fields and the color.

(I will ask how to get it to boot from a Linux server in a separate thread.)

To tjc: When you say you're seeing the same problems with DVD, is this with a set-top box, or with your MythTV box playing a DVD?

Are you using a composite connection or an S-video connection? If you have the option to use S-video with your TV, you should.

Have you tried using a TV tune-up DVD to calibrate your DVD?

tjc: in the "misery loves company" department, here is a long informative thread from the AVS Forum on Radeon S-video output under Windows, and why it stinks:

http://www.avsforum.com/avs-vb/showthre ... ght=fields

Highlighting "fields" because you'll see some posts in there that basically state there is NO way to preserve fields with anything other than a PVR-350, or a Sigma Xcard (which appears to have no Linux support).

As I tried to emphasize, the problem is the computer's s-video output to my TV. No matter what the image source, whether it be recorded by the PVR 250, a DVD being played in the internal DVD drive, graphics generated by the computer, ... No matter what the quality of the data going into it ... The output of the:
on my TV is mud.


See above. I'm actually considering trying the composite output adaptor in the hope that the TV will treat it differently, or that I can run it through some other piece of hardware to boost it.


No. Not much point if I can't even get an acceptable image on the TV using the computers output to start with. It'd be like painting a skunk grey in the hope of passing it off as an elephant.

Like I said I can tell the difference. I do not watch any of the programs that you mentioned, The next thing I am going to use is vga-> component convertor, but I have not had the money or desire to set this up yet. I am hoping at some point to experiment with the pchdtv card, and at that point I will switch to the converter to get the higher res anyways.

_________________
Have a question search the forum and have a look at the KnoppMythWiki.

Xsecrets

Xsecrets,

As I am in the UK and have a scart connection with RGB, I was brave/stupid enough to try the approach of direct VGA to SCART through a very simple circuit. Now that the new Nvidia linux drivers support Interlaced modes, it is relatively simple. As long as the VGA modeline is interlaced, and matches the expected input of your "monitor" (TV) then it should work.

ModeLine "720x576PALi" 13.75 720 744 800 880 576 581 583
625 interlace -hsync -vsync
Works for me.

RGB is at the right voltage levels (0 to 0.7v above black level), but the sync signals out of the VGA port are TTL (0-5V), and need to be dropped in voltage and combined to give a combined HV sync pulse.

Check out

http://www.qsl.net/dh1dm/tv_50hz_svga/ for the simple circuit I used.

The 10K resistors should be somthing much lower though, as the input impedence of the scart synch is 75 Ohms. I used 330 Ohms.

Also I found

http://www.idiots.org.uk/vga_rgb_scart/ useful.

Again be careful. If your new TV goes up in smoke, you are on your own

ceenvee703
Wandering off topic, for Linux on the MVP then check out

http://www.shspvr.com/forum/viewforum.php?f=38 (I'm red321 on that board as well)

and

http://mvpmc.sourceforge.net/

tjc: I realized afterward that you did mention you were using s-video. Sorry for missing it the first time.

Did you read that AV Science forum link I posted?

I also seem to remember a few years ago, some kind of modification people were doing to Nvidia cards to dramatically improve TV-out... something like cutting leads on some resistors on the board. I haven't tried searching for that, and it may be so old as to be irrelevant now, but it may be worth investigating.

I'd highly recommend avsforum for issues of improving image quality.

red321: thanks for the links! Another linux project to bang my head against... :-/

tjc,
I have the same symptoms as you have described, however, I had came to the conclusion that it was a capture issue. I have the same contrast/brightness issues whether it is being viewed on my 43" Sony via S-video out, or on my Compaq monitor via analog VGA connector (all my video out options on a single SiS AGP315T). I don't have my DVD drive working yet, so I can't test that.

It has really baffled me!

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ECS K7VMM+
AMD Athlon 1600+(1.4Ghz) CPU
nVidia MX 440 w/TV-out AGP
KWorld PCI-Xpert Tuner
512MB PC100
80GB Seagate

I'm getting more anecdotal evidence that the S-Video TV out on FX5200 based video boards is better. One guy actually did a DVB side by side comparison between the direct feed and a cheap (~$70 (his price was 550 Swedish Kronor)) Gainward FX5200 based card and saw essentially no difference. I'd still like to get more feedback on this, so if you're using an FX5200 based card, and can do a side by side comparison (tune the TV to the same channel as the Myth box and flip back and forth between the two video sources) I'd really like to hear your results.

Note - Most cartoons are really a good baseline for comparison because of the strong and fairly consistent colors, with live action the ligting leads to far more variability.