Improving Picture Quality in MP (2 Viewers)

[KevL]

I have been playing with MP and similar packages for a long time. With recent improvements in graphics cards and
processors (particularly using DXVA and similar techniques) it is now possible to get picture quality approaching
that of decent quality set top boxes and stand alone DVD players.

I say - approaching - as I have never quite got it to be quite as good. Typically I notice microjudder, a lack of
fluidity to motion, some motion blur and a general "softness" to the picture. An excellent illustration of the
fact that the typical HTPC doesn't quite cut it is to try and watch the Bloomberg channel which has a ticker tape
running showing stock market prices. From a set top box this runs smoothly. From an HTPC this ticker tape is a
horrible jerky mess. I guess this makes sense as set-top boxes do decode and picture processing in hardware whereas HTPCs do some (most???) of the processing in software - and the processor is easily distracted by servicing windows etc.

Of course the ticker tape is just moving video so if it looks so obviously poor then what is the HTPC actually
doing to the video when some person has the audacity to move across the screen in a film?

Ive done all the normal tweaks, played with different decoders and combinatations of settings.
I guess I am being quite picky but the above effects are very obvious on big plasma displays where one can switch
between HTPC and settop box sources and make direct comparison.

Then I discovered where I had been going wrong.

My plasma screen has a native res of 1366x768. It has HDMI and VGA inputs either of which can be connected to a PC and with some effort (possibly involving Powerstrip or similar) can get a picture which fills the screen and is
quite watchable.

I notice that when I set the HTPC to output 1280x720@50Hz progressive by HDMI then my mostly PAL Standard
definition signals get scaled by the HTPC to 1280x720 and then get displayed on the plasma which then scales the
picture again to 1366x768. Picture quality is OK but not brilliant.

I can also output 1920x1080@50Hz via HDMI but picture is even worse (really quite poor).

So then I find that with Powerstrip I can get an even better picture by outputting 1368x768 (near native panel
res) at 50Hz via VGA. Picure is now the best yet.

But still the picture quality is not as good as the set top box. The "Bloomberg test" is failed dismally and
there are motion artifacts and blurring and softness.

So now the fix.

Just out of interest I now set the PC to output 720x576@50Hz progressive via HDMI. It had never occurred to me to use such a low res.

Picture is now actually better than set-top box. Bloomberg ticker tape is now as smooth as silk and there is no
problem with motion and no softness in the image. Picture from many set-top boxes (mine included) suffer from the Chroma bug. This artefact is absent from most HTPC implementations - hence picture is better than set-top box.

I think what this is suggesting is that HTPCs do not make very good scalers. (Or that the hardware scaler in the
plasma is head and shoulders above the typical PC in this regard).

So now I'm not burdening the PC with any scaling duties. I just let the plasma screen sort it out.

I guess this makes sense when you think about it, but I hadnt.

So am now investigating how to have the MP menu in 1280x720 and then have it switch mode to 720x576@50Hz
progressive when showing SD video full screen and 1280x720@50Hz when showing HD full screen.


Hope this helps others struggling with PQ on an HTPC.

Maybe I'll find that everybody already knew this


Kev

 

[tourettes]

Sorry, but the assumption you made is wrong:

I think what this is suggesting is that HTPCs do not make very good scalers. (Or that the hardware scaler in the
plasma is head and shoulders above the typical PC in this regard).

Based on your experience looks like the TV won't handle the PC input correctly (this is pretty common for many LCD/Plasma TVs). Video cards itself are almost always doing a better quality scaling than the today's TVs. Almost many times such stuttering you are seeing is a result of TV itself, no one knows what the TVs are doing internally, some are even converting the 50 hz video to 60 hz and then back to 50 hz.

So, basicly when someone is buying a new TV he/she should do some studies how well the TV will work with PC connected to it. Many different forums are good place for such queries (AVS forum for example).

 

[KevL]

Have you tried the Bloomberg test on your setup? Is text silky smooth, no stutter/ judder???

I have an 8th gen Pioneer plasma. Well respected for PQ - there are better sets but it is well into the diminishing returns re cost versus performance. As you will see from my system config - my ATI graphics card is of recent vintage and though not gaming quality ought to be OK for SD video.

All I can say is try it on your setup - unless your gear is producing better PQ than your set-top boxes already. If so please post setup details.


Kev

 

[tourettes]

Have you tried the Bloomberg test on your setup? Is text silky smooth, no stutter/ judder???

Yes, all news tickers are smooth scrolling. LCD picture quality (LCD does some scaling) is a little bit compromise as I have 1366x786 native panel but I'm "forced" to feed the 720p picture into it as the beamer is also sharing the same source. Better to make some compromise on the 32" display than on the 100" one.

 

[KevL]

All I can say for sure is that my plasma is better at scaling than my fairly modern HTPC - by a large margin.

I can't be sure that you are correct when you say that stuttering is a problem created by the TV and the PC is blameless. How can one know?

In my case I'm using the same HDMI channel on the TV and 720p @50Hz is worse than 576p @50Hz for SD material by a huge margin.

Anyway if you have better than set-top box quality already then you have found a way of setting your gear up correctly. I hadn't


Kev

 

[gxtracker]

Just out of interest I now set the PC to output 720x576@50Hz progressive via HDMI. It had never occurred to me to use such a low res.

Picture is now actually better than set-top box. Bloomberg ticker tape is now as smooth as silk and there is no
problem with motion and no softness in the image. Picture from many set-top boxes (mine included) suffer from the Chroma bug. This artefact is absent from most HTPC implementations - hence picture is better than set-top box.

I think what this is suggesting is that HTPCs do not make very good scalers. (Or that the hardware scaler in the
plasma is head and shoulders above the typical PC in this regard).

HTPC's have the power to be much better scalers than those built into television sets - simply due the fact that every part of the processing stream can be customized and modified to the viewers taste. The difference of course is that manufacturers have dedicated engineers working on image quality and the rest of us have hobbyist videophiles who tinker with settings to rely on.

If setting your resolution to the native size of SD material produces no stuttering, but then does with anything higher, than that tells me a piece of the chain isnt able to keep up with it's decoding/display duties - whether that component be hardware or software. Even on my modest HTPC, I set my display to 1360x768 (native 1080p HDTV) and scrolling tickers are just as smooth as if they were coming out of a dedicated STB. I have most of the video processing disabled in the TV itself, since doing so can speed up response times and create other benefits on some sets.

IMO, I would rather let the HTPC deal with the scaling duties, and use the display just as a display.

 

[KevL]

Its been a while since I tried ffdshow as a scaler. I've just been using VMR9 fullscreen exclusive to sort all that out. The only settings it has is the amount of filtering it uses - unless I'm missing something - and I can't rule that out.

You might well be right about my HTPC not being setup correctly. There are an awflul lot of variablesto play with. I think I have played with all the permutations I can think of but might have missed something. There again just type stutter and judder into the MP search box. Maybe I'm not alone with this problem.


Kev

 

[tourettes]

If setting your resolution to the native size of SD material produces no stuttering, but then does with anything higher, than that tells me a piece of the chain isnt able to keep up with it's decoding/display duties - whether that component be hardware or software.

There is still the other option. Unfortunately some TVs won't support all refresh rates on:

1) non-native display resolutions
2) VGA input

Most of the TVs are still pretty picky about the signal characteristics you are feeding to them.

 

[KevL]

There is still the other option. Unfortunately some TVs won't support all refresh rates on:

1) non-native display resolutions
2) VGA input

Most of the TVs are still pretty picky about the signal characteristics you are feeding to them.

The above is very true of course but....

My TV accepts both of the resolutions I am comparing via its HDMI input at 50Hz. (its user manual is quite explicit on the subject)

When PC desktop res is set to 720x576p@50Hz picture is stunning on PAL SD material..
When set to 1280x720p@50Hz picture is poorer.

For these settings I simply go into catalyst control centre and select them. No complicated resolutions via powerstrip/12noon etc involved.

If the pioneer did such a really bad job of upscaling 720p then I suspect they wouldn't be as well respected for PQ.

Kev

 

[gxtracker]

Most of the TVs are still pretty picky about the signal characteristics you are feeding to them.

That is very true - My TV has a specific port split between HDMI and DVI. If i set the HTPC to 1360x768 (PC Resolution) then the video options i get are related only to a PC and many of the advanced filtering settings are disabled. If I set the resolution to 1280x720 (720p) then all the HDMI advanced filtering options become enabled such as correcting the RGB values.

I cant think of a definite reason of why your picture looks better at SD resolution. Maybe because of the low res signal the TV enables certain features for upscaling and filtering the video? Is a stuttering picture the only issue? If so, im still inclined to believe performance related issues.