(2012-08-04, 01:38)jmarshall Wrote: Wide zoom is the non-linear stretch.
Wide Zoom is not a non-linear stretch. It is a linear stretch except that the stretch ratio is slightly different in the x and y plane (unlike zoom where the stretch ratio is the same). Let me explain: in order to make a 4:3 video fit a 16:9 screen you must either loose pixels or distort the image (ie change the pixel ratio) or put up with black bars. This is how the various modes work:
- Stretch 4:3 - retains the original pixel ratio and stretches the image equally in both directions so that the vertical size matches the screen height. However this does not fill the screen in the horizontal plane so the video is displayed with black bars left and right. No distortion, No missing pixels, Black bars.
- Zoom - goes one stage further and continues to stretch the image until the horizontal size matches the screen width. However pixels on the top and bottom are now off screen and thus missing. No Distortion, Missing pixels, No Black Bars.
- Wide Zoom tries to improve on zoom by stretching the image slightly less in the vertical plane than the horizontal plane to retain more pixels at the cost of some distortion (slight squashing of the picture). Mild distortion, Less missing pixels, No Black Bars.
- Stretch 16:9 - like Wide Zoom, the image is stretched by different ratios in the vertical and horizontal planes so that the vertical size matches the screen height and the horizontal size matches the screen width. However the image is even more squashed than with Wide Zoom. This fills the screen and retains all the pixels, but at the expense of image integrity. People appear short and fat. Maximum distortion, no loss of pixels, No black bars.
In each of these cases we either have: black bars, missing pixels or unacceptable distortion.
Non-linear Stretch tries to overcome this as follows: like Stretch 16:9 the image is stretched in both directions until the vertical and horizontal sizes match the screen height and width. However instead of using the same stretch ratio across the whole horizontal plane (linear stretch), it varies the ratio (non-linear stretch) so that pixels in the centre of the screen are un-distorted but the rate of distortion slowly increases as you move to the horizontal edges of the screen. Note that stretching in the vertical plane is linear. The distortion is therefore negligible in the centre of the screen where most of the action takes place. Whilst the distortion at the edges is greater that Stretch 16:9, this is not very noticeable in practice. The result is: Acceptable distortion, no loss of pixels, no black bars.
MediaPortal does nonlinear stretch very well. People appear natural and the video seems like it was shot in 16:9 mode. Only on some panning shots do you notice the distortion at the edges, but this is a very small price to pay for the more realistic presentation.
Now back to my original question - Does xbmc have a non-linear stretch mode as described above?