Picture quality MP1.0 vs DVBviewer (2 Viewers)

[Mister Bean]

Hi Tourettes and all others,

Very interesting stuff. . . .

I have done some more investigation. I'm almost convinced that the difference in picture quality between DVBviewer and Mediaportal can be 'downdrilled' to the MediaPortal application itself. The reasons why I am thinking that are:
- DVBviewer uses the same graph as DVBviewer.
- It is MPEG2 decoder independent. Problem occurs with almost every MPEG2 (hard- and software) decoder. @ Tourettes, I've attached also a screendump of the Cyberlink Decoder settings. Tweaking of these settings gives me no improvement.
- It is renderer independent. Problem occurs with VMR9 and EVR (under XP).
- When I make a recording with Mediaportal and played this back with DVBviewer --> picture is perfect!
- Tweaking of decoder settings, VMR filtering or Catalyst settings gives no improvement.

It seems to be there is going something wrong in the processing of the picture in Mediaportal or it has something to do with the VMR/EVR settings that are used by Mediaportal.


In the attached zip-file you will find one small recording and two captured frames taken from this recording. It is best to open these captured frames in Windows Paint. Look specially at the (collar) of the shirt the presentator is wearing. In Mediaportal there is much more aliasing visible then in DVBviewer.

I'm sad to conclude that the picture quality of DVBviewer is better (more purely, less aliasing) then in Mediaportal.

This aliasing problem occurs only with MPEG2. MPEG4/H.264 transmissions (1080i and 720p) are looking wonderfull. Also 1080p content (MKV rips) are giving perfect quality.

I'm looking forward to all replies to this interesting thread!

Thanks in advance.

Nico

 

[tourettes]

Very interesting stuff. . . .

When comparing side to side those screen shots (they contain only small difference) I think the MP one looks better (just an opinion).

Looks like DVB viewer has more smoothing, especially if you look at the text at the bottom of the screen.

It's pretty easy to see that the DVBViewer shoot (or MP in that case you have made a test where the file names are switched on purpose )

1) Open both pictures in Paint (in fullscreen)
2) Zoom to 800%
3) Scroll down to right bottom corner
4) Compare details on "1" char

That same "sharpness" (not sure if we can call it sharpness on MPEG SD video ) will make MP look to have more decoding artifacts as not much smoothing is applied to the whole image.

...now, I'm not sure where the difference in "blur" level comes, but its not any deinterlace error I would assume, but instead something else.

PS. I definitely wouldn't loose my sleep because of that difference as you can see the picture quality itself is horrible on that sample .ts Just check how much mpeg blocking artifacts there are visible, those are much more visible than the slight smoothing difference.

 

[Mister Bean]

tourettes
I agree with you that the quality of the Dutch broadcasters on Astra (Canal Digitaal) is horrible due to low bitrates (avg. 3Mbit/s), but . . . . If a tune in to a good quality MPEG2 transmission (ARD/ZDF) which has a bitrate of 7Mbit/s the picture quality is looks really better with DVBviewer. These 'artificial sharpening' or aliasing become worse in the small details of the picture (for example hair). Maybe this is subjective, but I'm an AV enthousiast and find these picture distorsions annoying. Again, it is only noticeable on good quality big screens (plasma's), thats maybe the reason why less people have complained about this. Unfortunately is this 'problem' still unsolved and the question still remains. What is different in pictureprocessing between Mediaportal and DVBviewer?

At this moment my (8 year old) STB connected via SCART beats my HTPC in picture quality with MPEG2 transmissions.

 

[tourettes]

@tourettes
I agree with you that the quality of the Dutch broadcasters on Astra (Canal Digitaal) is horrible due to low bitrates (avg. 3Mbit/s), but . . . . If a tune in to a good quality MPEG2 transmission (ARD/ZDF) which has a bitrate of 7Mbit/s the picture quality is looks really better with DVBviewer. These 'artificial sharpening' or aliasing become worse in the small details of the picture (for example hair). Maybe this is subjective, but I'm an AV enthousiast and find these picture distorsions annoying. Again, it is only noticeable on good quality big screens (plasma's), thats maybe the reason why less people have complained about this. Unfortunately is this 'problem' still unsolved and the question still remains. What is different in pictureprocessing between Mediaportal and DVBviewer?

As DVBViewer is closed source I can only guess what's different in those two and based on the picture I would assume DVBViewer does some smoothing (as I know that MP is at least not by any purpose doing any sharpening or any other post processing to the picture).

I think we need to find some reference MPEG decoder that can be used as comparision target to see is MP sharper than the comparision target or is DVBViewer using some blur / smoothing. So, does anyone know some reference MPEG decoders (non-directshow) that could be used for the analysis?

At this moment my (8 year old) STB connected via SCART beats my HTPC in picture quality with MPEG2 transmissions.

Could it be that you like more the smoother picture? SCART is most likely producing smoother picture than the HTPC connect to the tv (if you are using digital connection, what I assume you are).

btw. I'm also pretty picky when it comes to picture quality, especially as with >100" projector image the small details are pretty visible

 

[rtv]

@tourettes
These 'artificial sharpening' or aliasing become worse in the small details of the picture (for example hair). Maybe this is subjective, but I'm an AV enthousiast and find these picture distorsions annoying. Again, it is only noticeable on good quality big screens (plasma's), thats maybe the reason why less people have complained about this.

Maybe tourettes and me have a different point of view here. As we're using MP on a screen which is more than 4 times the size of yours we're even glad about the picture looking a bit less "processed & dull". In fact noise reduction & smoothing is one of the worst things when you watch anything else then comics/manga. Some people with good projectors even prefer adding "artificial" noise (which sounds rather stupid) via ffdshow to get a more "film like" effect.

 

[grubi]

For me it looks like postprocessing (Edge Enhancement) artifacts for the MP picture.
Did you ensure that all post processing (Noise Reduction + Edge Enhancement) done by the grafic card is disabled (Look at the avivo tab in CCC).

 

[tourettes]

For me it looks like postprocessing (Edge Enhancement) artifacts for the MP picture.
Did you ensure that all post processing (Noise Reduction + Edge Enhancement) done by the grafic card is disabled (Look at the avivo tab in CCC).

That indeed could explain the difference in sharpness.

 

[grubi]

I just did the tests on my system (comparing you recording between MP and DVBViewer) and I have to admint that I could acknowledge your observations.
It looks like the picture of DVBViewer is better scaled than the MP one (better aliasing).
I also verified that both graphs in use are identical.
This is really strange.

Will try to play around with VMR settings in MP next.

It seems that disabling the options "Use nonsquare mixing for scaling" cures the problem.
The question remains why - as it should increase quality and not decreas it.
I'm not an expert on this but IIRC the option should avoid that an image is scaled twice under certain circumstances. Scaling a picture twice could indeed smoothen a picture which could lead to a more pleasent apearance.

Mister Bean: Maybe you could give it a try and report back. I also found that all the scaling algorythms do not show any difference which they obviously should.

 

[tourettes]

It seems that disabling the options "Use nonsquare mixing for scaling" cures the problem.
The question remains why - as it should increase quality and not decreas it.
I'm not an expert on this but IIRC the option should avoid that an image is scaled twice under certain circumstances. Scaling a picture twice could indeed smoothen a picture which could lead to a more pleasent apearance.

Non-Square Mixing (Windows)

If your application uses a custom allocator-presenter with non-square mixing mode, be aware that the composited image may have a non-square PAR. The allocator-presenter must scale the image to a square (1:1) PAR.

I wish Eabin was here to check the VMR9 code I would assume I haven't seen such behaviour as I have always used EVR on Vista.

 

[grubi]

Maybe I will setup Vista on that machine (for testing) to see how EVR (HW) compares to that.
Interrestingly as Mr Bean already stated switching to EVR (software based) on WinXP shows the same artifact like VMR9 with Non-Square Mixing enabled.