Aspect ratio incorrect on 16:10 LCD screen

[stustunz]

what decoder are you using ?
make sure its not set to default

have a think about what you are saying aswell dont you think there would be more complaints if it were wrong
maybe its a setting or something in your system that is causing the issue
beleive me im pretty sure its not gbpvr

[sub]

He is correct that you need to have you video decoder set to something other than 'system default' for it to do this.

Stustunz I have tried F7. If I set <AspectRatioMode name="LetterBox" ratio="0,0.05,1,0.95" /> it displays the picture correctly. Thanks.

That fact this worked makes me think Stustunz was correct that the decoder setting was your problem.

[Astrophysics]

Agreed (with earlier posts... somehow missed the last couple); the pixels on my TV -- though it is a 16x9 aspect ratio -- are not entirely square as displayed by my computer. I got out the measuring stick, calculator, paper, and pencil and worked out by hand all the precise percentages to plug in to my config.xml, and it works beautifully. Granted, I would love to have the configuration detect whether I'm using my TV in 720p mode or 1080i mode, since I need 4x3 aspect ratios separately programmed for each... but that's neither here nor there. Yes, it might be useful to include a block of commented-out aspect ratios for people with 16x10 or 5x4 displays that they can then manually enable, but the point is that the capability is there to handle any shape and size of display -- don't be afraid of the arithmetic! There's a good tutorial on the wiki if you search for it.

[Agamemnon]

It's not my decoder. The video window aspect ratio is 16:10. This aspect ratio is set by GB-PVR not my decoder. I have taken a screen capture and measured it. It's 800x500 pixels and always resizes with a 16:10 ratio. The reason for this is because the software is assuming that my screen is 16:9 ratio and has non-square pixels. It should not be doing that. It should be assuming square pixels like Windows Media player does and displaying a 889x500 pixel window.

If you are using HDMI to transfer a 1920x1080 picture to your HD TV then the aspect ratio of that resolution (16:9) is already equivalent to the screen resolution ratio, which means square pixels are being used by the HDMI controller and being input to the upscaling/downscaling/processing chip on your TV even if your TV resolution is only 1440x1080 like some wide screen TVs are which don't use square pixels.

[sub]

It's not my decoder. The video window aspect ratio is 16:10. This aspect ratio is set by GB-PVR not my decoder.

I'm not saying its your decoders fault. I'm saying you have to have your video decoder set to something other than 'system default' in the config app - this is so that GB-PVR can find the correct filter to ask what the current aspect ratio of the video stream is. Once GB-PVR knows the aspect ratio of the stream, then it chooses the most appropriate aspect ratio mode from the <AspectRatioModes> list in config.xml.

As you've already indicated, you got the correct aspect ratio when you forced it to "0,0.05,1,0.95".

If you are using HDMI to transfer a 1920x1080 picture to your HD TV then the aspect ratio of that resolution (16:9) is already equivalent to the screen resolution ratio, which means square pixels are being used by the HDMI controller and being input to the upscaling/downscaling/processing chip on your TV even if your TV resolution is only 1440x1080 like some wide screen TVs are which don't use square pixels.

You are trying to over simplify things. Tube TVs and plasma usually have rectangular pixels. LCD TVs often have square pixels. GB-PVR needs a scheme that accommodates both.

Video resolution and screen resolution are also two different concepts. Remember a widescreen 16:9 DVD has a video resolution of 720x480, while a 4:3 DVD also has a video resolution 720x480.

[Agamemnon]

I have selected the MPEG decoder manually and GB-PVR is still not displaying the aspect ratio properly. Even with letterbox set to <AspectRatioMode name="LetterBox" ratio="0,0.05,1,0.95" /> there is still too much underscan and timing and switching signals from BBC News24 are being displayed on the top of the picture when they sould not be. The problem as I have already said is that GB-PVR is using a 16:10 ratio window filled by a squashed-sideways 16:9 ratio picture. The ratio of the video window should be 16:9 even on a 16:10 monitor. The only way to correct this fault properly and maintain the right amount of overscan is for GB-PVR to use square pixels and display the video in a 16:9 ratio window and stop assuming that the monitor is 16:9 and using rectangular pixels which it is not.

Oh and BTW 16:9 widescreen DVD resolution is actually 702x480 NTSC or 702x575 PAL. It's 720 only for 4:3 material. I hope your scalar actually realises this.

[sub]

You're confused and switching back and forth between aspect ratio and the desire to crop parts of the picture. These are two different concepts.

I have a 16:10 LCD monitor sitting here on my desk running 1920x1200. By simply setting <AspectRatioMode name="Fill" ratio="0,0.05,1,0.95" /> in config.xml, when I'm in the auto aspect ratio, and attempt viewing a channel transmitting 16:9 video, I automatically get the correct 16:9 aspect ratio on my 16:10 display. See the attached screenshot.

With this setting it gives exactly the result I'd expect. GB-PVR is displaying the 16:9 video within a 1920x1080 view port on the screen, with 60 black pixels on the top and bottom of the screen (filling the remainder of the 1920x1200 screen).

The problem as I have already said is that GB-PVR is using a 16:10 ratio window filled by a squashed-sideways 16:9 ratio picture. The ratio of the video window should be 16:9 even on a 16:10 monitor.

That is exactly what GB-PVR is doing. See screenshot. Do you think there is something wrong with the aspect ratio of this picture GB-PVR is producing?

[stustunz]

sub wont agree but mpeg decoder wont work properly either select something else
i can almost garentee it will work if you select cyberlink or another decoder

[Hairy]

I've found that with my 16x10 TV, the best way for me is to treat it like a 4x3 set. I set TvShape to 4x3 and over compensate for the compressed image by adjusting the VerticalZoom. That way all widescreen video, from 16x9 to the various widescreen aspect ratios used in film, looks correct.

I then add a separate AspectRatioMode for 4x3 to scale it back down to the correct position. With this set up I have just 2 Aspect Ratio Modes, Auto which handles everything widescreen and 4x3 mode for the 4x3 content, so it's simple a single press of a button to switch between the two.

It's just a different suggestion to try out.

Code:

<!-- zoom control -->
  <HorizontalZoom>1.01</HorizontalZoom>
  <HorizontalOffset>0</HorizontalOffset>
  <VerticalZoom>1.16</VerticalZoom>
  <VerticalOffset>0</VerticalOffset>

Code:

<TvShape>4x3</TvShape>
  <AspectRatioModes>
  <AspectRatioMode name="Auto" ratio="0,0,0,0" />
  <AspectRatioMode name="4:3" ratio="0.080,0.080,0.920,0.920" />
  </AspectRatioModes>

[Agamemnon]

Here is a screen capture (aspectratio.jpg) I have taken of BBC News 24 view in GB-PVR with the letterbox set to <AspectRatioMode name="LetterBox" ratio="0,0.05,1,0.95" /> and all other settings set to default. As can clearly be seen, time and switching codes are displayed at the top of the picture when they should have been overscanned and at the bottom of the screen the news ticker is too wide, whereas it should have been cropped 4 scan lines below the clock. The above setting narrows the overscaan to display more of the picture from top and bottom in order to achieve the 16:9 correct aspect ratio inside the 16:10 window, and it should not be doing that.

GB-PVR does not handle aspect ratios and overscanning properly. If I attempt to correct the oversscan by setting the vertical zoom settings to <VerticalZoom>1.09</VerticalZoom> as well the picture becomes even worse than before. Not only do the black bars almost disappear but instead of overscanning more GB-PVR overscanns less, as can be seen from the other screen capture (aspectratio2.jpg).

It is also clear from both screen captures that GB-PVR is displaying the picture in a 16:10 window even though it knows it should be displaying the TV picture in 16:9 ratio. Why is it doing this? Is it assuming that my 16:10 monitor is using rectangular pixels instead of square pixels.

Why isn't GB-PVR using a display window with a 16:9 aspect ratio. For PAL 16:9 widescreen TV the correct aspect ratio multiplication factor is 1.46 to 1. Thus for a PAL 702x576 image 702 is multiplied by 1.46 in order to give the correct display image of 1025 pixels by 576 pixels which gives a screen ratio of 1.78 to 1 or 16:9. This 1025x576 pixel image should then be rescaled equally in both directions. Instead of using a multiplication factor of 1.46 to 1 for PAL, GB-PVR uses a multiplication factor 1.31 to 1 which gives an image of dimensions 920x576 which is 16:10!

Note that widescreen TV uses a displayable picture area of 702x576 or 702x480 pixels whereas standard narrow screen TV uses a displayable picture area of 720x576 or 720x480 for PAL/SECAM and NTSC respectively, the rest is used for blanking.