New zoom mode: 4/3 -> 16/9 non-linear distortion

[mystic2k]

Started on: 2007-04-09
last update: 2007-04-09

Summary:
Implement a zoom mode using slight cropping and non-linear distortion to optimize the scaling of 4/3 images on 16/9 screens.

Area:
My TV, My Videos

Description:
First let me say I've read pretty much all of the existing threads on this topic, but I couldn't find any containing an answer from the dev-team about the feasibility of this.

I've just switched to MP from MCE 2005 and this is the ONLY feature I miss. MCE has a zoom mode that crops a small part of the top and bottom, then stretches/compresses the image to make it 16/9, but only on the sides of the picture, leaving the central part pretty much untouched. This is also found on pretty much any widescreen TV set, although with slightly different approaches (no cropping for example).

I realize some people don't like this depending on the type of program watched (14/9 zoom can be a better alternative), but I still believe it would be a highly valuable addition to MP as it remains by far the best compromise for those wanting to scale 4/3 content without any letterboxing.

Also, please note that with many LCD/plasma TV sets, you can not use any kind of image processing when using the VGA/DVI input, so using the TV's own zoom mode isn't an option here.

Lastly I would like to insist that if (fingers crossed) someone ends up developping such a feature for MP, the quality of the implementation can vary greatly depending on the values used. Let me stress that the MCE 2005 one is probably one of the best I've seen so far (including high-end TV sets), as the image distortion is barely noticeable even on the sides. I would be glad to help figuring out the exact values that are used by MCE, please let me know if needed. Here's a link that shows an example of the MCE mode in action :

http://www.codinghorror.com/blog/archives/000418.html

Thanks in advance for any feedback !

(My first message on these forums and it's already a request... so I also wanted to say a big THANK YOU to all those working hard on this superb piece of software, please keep up the fantastic work !!)

[lkuech]

Hi mystic2k.

I was also surprised that MediaPortal lacks in such an important point as I was stumbled about it a few weeks ago. Maybe it is because many people use MediaPortal on there normal PC with the normal 4/3 monitor... not sure...

To build a HTPC that have a decent WAF (woman acceptance factor) that is something I have to solve first. Because of this I have build a new zoom mode that is based on the 14:9 zoom, but stretched over the whole screen. With other words the picture is cropped 12,5% of the upper and lower part of the picture and stretched the rest over the screen. This is a compromise between "stretched" and "zoom".
Of course this is not as elegant as a real smartzoom that handles the center of a picture in a different way as the borders, but it is much better than a simple stretch.

I have plans to post it in the next days. Maybe the devs are will implement it sooner or later (Maybe before the next stable version is released). Unfortunately the implementation of a new zoom mode makes changes in many files necessary, so it is not done with a few clicks...

Find attached the sample screenshots of the new zoom mode.

BTW: Because of the WAF I currently develop a plugin that automatically switches to the zoom mode if a 4/3 signal was detected. This maybe interesting for you as well. Here is the link: http://forum.team-mediaportal.com/vi...in-t21365.html

Bye
Lars

[knutinh]

Originally Posted by lkuech

I was also surprised that MediaPortal lacks in such an important point as I was stumbled about it a few weeks ago. Maybe it is because many people use MediaPortal on there normal PC with the normal 4/3 monitor... not sure...

I am guessing that most people interested in video thinks that it is a subjectively bad feature? I, for one, do.

Of course, having a feature that I dont like is no problem to me as long as it can be disabled, but in a open source project, the personal view of the developers will influence what they implement?

-k

[mystic2k]

I am guessing that most people interested in video thinks that it is a subjectively bad feature? I, for one, do. (...) in a open source project, the personal view of the developers will influence what they implement?

In my opinion the question is : what's the objective of MP's dev team ? Is it to cater mainly to video enthusiasts, or is it to reach a wider audience and become the new standard in HTPC software ? This feature certainly has its faults, but to the casual user its a real must-have (WAF is a major concern for many of us, and I totally agree with Ikuech on this one).

The thing is, when I see the kind of very advanced features that are being developed right now (like zoom mode moving the subtitles from the bottom part of the screen into the zoomed picture, or auto-detection of the proper zoom mode based on real-time analysis of the source), I'm thinking that developing a non-linear zoom mode based on fixed scaling values must not be that difficult for these experts (sorry if I'm wrong here - just supposing). Given the huge popularity of widescreens nowadays (both TV's and computer monitors) I really think that this belongs in the basic aspect ratio featureset of a good HTPC front-end - then it's up to the end user to choose to use it or not.

Also, I understand how some of you consider it bad because the image ends up too distorted, but I really encourage you to have a look at the MCE implementation if you have a chance. I was really impressed at how natural the scaled image looks compared to many TV-sets with the same function, and I now use it all the time (and believe me I hate distorted pictures too). I will do some testing tonight to understand exactly what MCE does to achieve this, and will come back to you guys with the results.

I would really appreciate if someone could advise on the technical challenges this might represent from a coding point of view. I'm ready to do as much as I can to facilitate their work.

Cheers,

Laurent

[spenca]

hi all!

this is also a very interesting feature for me! since i use a htpc for watching multimedia, it's not possible for me to use this widescreen mode of my tv any more. and i missed it so much, because it offers so much advantages over 4:3 or pure 16:9 modes! just think of damages on plasma tv sets which are driven in 4:3 mode all time!

greetz!

Mario

[mbuzina]

FDDshow already has a non-linear zoom mode. So you would have to enable FDDshow postprocessing and set the zoom modes.

Unfortunatly, this is not tightly integrated, turning on & off is difficult etc. etc. etc.

I do use this feature on my Philips LCD TV (37") and I turn it of for films or other things where this disturbs my viewing experiance. For simple everyday watching such a mode is fine. So a version which is integrated into the zoom features (maybe including the auto-zoom / crop plugin), can be customized and turned off is a good thing to add to mp.

[revs]

Ill put another vote in for this feature!

[mystic2k]

Hi all,

I did some testing with MCE 2005 last night. I created an uncompressed AVI video containing a grid of 1024*768 pixels (each square 32*32 pixel) and played it in MCE using "intelligent zoom" on my 1360*768 LCD. Examining the resulting screenshot allowed me to determine the zoom/stretch values that are being used :

1) The image is zoomed by 9.1%, resulting in a slight cropping of the top and bottom portion of the picture.

2) The values used for the non-linear stretch can be found in the attached file (sorry for the poor quality... but it's readable !)

Looking at these results, I think that the reason the MCE implementation looks so smooth is because as you can see in the attachment, even the very center of the image is stretched by 8.9% (while in some implementation I think it remains totally untouched). This and the top/bottom cropping results in lower stretching values needed on the sides, therefore less noticeable distortion.

I don't know what I can do to help further and encourage one of the MP devs to implement this, but anything that can be done without programming knowledge should be ok ! Let me know !

Cheers,

Laurent

[Schrauber]

I would also like to see such a Feature in MP.

The thing is, for everyday viewing it is very nice. Most shows on Tv remain 4:3. And for this shows its a nice mode.
I can use the superzoom of my TV set even with MP. But doing so, a part of the OSD is cut off. So it would be much nicer to have this mode directly in MP.

Anyway, many thanks to the devs for this nice peace of software.

[bigj]

This feature would be nice.
As to the implementation:

I'm not sure how the VMR9 frames reach the screen.
I've always assumed there is a simple D3D quad (two triangles) and the video frames are applied as a texture.
If this is the case, it would be trivial to reprogram the quad to be split into 1:N variable width vertical strips. The video is always displayed at full screen resolution. There should be a profile per stretch ratio, so that at 1:1 (true widescreen source on true widescreen destination device) the current single quad (strip) is used, at 4:3->16:9 stretch the profile_4_3_to_16_9 is used etc. The profiles are a simple text file that defines the number and ratio of the strips for that stretch ratio.

But, I'm suspicious that the code to present the VMR9 video isn't that controllable, since I've often wondered why there isn't MediaPortal controllable brightness-contrast-gamma; that should also be relatively easy to support if it (the video) is being presented as a simple texture on D3D geometry.
(as would skin definable warps, keystoning correction, mirroring etc etc)