If I have a 1080p video played by VLC-player and a graphic card that allows highest resolution 1360x768 on a monitor of native resolution 1366x768 (connected by VGA), how do all these components work together to render the final resolution?

They're all different 1920x1080 (video), 1360x768(graphic card), and 1366x768 (monitor).

  1. The max resolution of the display is defined by the number of individual pixels in the display.
  2. The graphics card can output to a monitor at any arbitrary size (within the limits of its processing capacity and whether it uses VGA, DVI, etc).
  3. VLC expands a compressed video file into individual frames, which for 1080p video are 1920x1080 pixels.

Your graphics card detects the display and, finding that the display's max resolution (1366x768) is lower than the graphics cards' own resolution, starts outputting at 1366x768 to the display. VLC decodes individual frames and presents them to the video card for display. Since the frames are larger (1080p) than the display's max size they get downscaled to 1366x768. Whether the video is downscaled by VLC using the CPU, or by the graphics card in the GPU, depends on whether the video is played using software or hardware decoding. This all assumes fullscreen mode. If VLC is playing in a window then the video gets scaled to the size of the video window; that's the only big difference.. the mechanics of the scaling process itself don't change, just the target output size.

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VLC itself will interpolate the video to the window size or in full screen to the computers resolution, generally whatever size that is, even much larger or a few pixels different.

The graphics card will output the computers resolution to the Analog VGA output.

To an analog Monitor:
The analog VGA input will then be displayed to the best of its ability, analogs horizontal streams can be easily interpolated and blend well, analog monitors often had areas that were not visualised (overscan) so it is possible that the 6 pixels extra would not change its pix=pix representation.

To a Digital Monitor:
In a digital LCD monitor with VGA input , the analog already has to be converted to digital prior to display, it is also likely to use an interpolation method, even if it was pixel for pixel it is still done as a stream, this 6pix differance would have the horizontal line end in 6pix black again, or interpolated with the rest of the stream. Any negative effects from this small of differance would either not be seen, or would so minimally effect the output as to not be an issue.

In this scenario the analog would be both the biggest blending, and the best interpolation (both good and bad) The lower computer resolution intital, and the analog (also if it needed conversion to digital) would be the biggest negatives. The minor issues here with the pixels would be the least of the deficiencies.

Short of replacing everything :-) I would think that you would still have a very nice picture, that will look fine , and these differances your seeing in numbers are usually worked out using the best method, and should not distract, or cause you to see it badly.
If your seeing a really bad picture it could be:
a) the settings in VLC for the way the video is interpoated and the render type.
b) software settings for the display both the OS, and the GPU software
c) if any interferances exists that seems unrelated to the picture, the VGA cable itself.
d) Settings in the monitor itself

Are you having any real problems with the setup?

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  • I'm curious as to why when I go to Display Settings and change the resolution for the 2nd monitor (I guess what Display Settings does is changing resolution of graphic card, not that I can change the native resolution), the size of full-screen video is affected. e.g. 1280x960, 1400x1050, 1600x1200 would give the same size fully covering the whole monitor. But others would give a size covering only part of the monitor. What does Display Settings do to the resolution? Why doesn't the graphic card just work between the video (1080p) and the 2nd monitor's native resolution(1366x768). – Myath Feb 13 '14 at 6:48
  • I am going to re-read your comment and Q more so I understand what your saying. for the moment you could see parts 2&3 of another post I covered some of that in. superuser.com/questions/713386/… If you could link to a picture you have in the question that shows the situations this would also help understanding your text. – Psycogeek Feb 13 '14 at 6:58
  • Ok, I think I know what your asking in the comment. Orignally analog monitors could do like 1 res and refresh rate, eventually they became "multi-scan" eventually (about) everything made was "multi-scan" and the name dropped off. The analog monitor without being sent ID information would analise the signal frequency it was seeing and attempt to display that frequency as best as it could. they still were not Vari-Scan. you computer can toss the monitor resolutions that it displays with borders , pillarbox or letterbox as it attempts to use the best method for displaying what it was handed. – Psycogeek Feb 13 '14 at 8:05
  • It is possible to have everything be 1=1 all over , match the res and pixels on everything. example play a 1080 on a 1080capable video card , with a 1080 monitor. There are also ways to force some aspects of things into 1=1 even if that clips , and shows a small 1=1 picture in the middle of its total res, and other methods. This interpolating (as best as it can) is a great feature, to solve all the problems, it is probably better than having a computer that only does one res, and a monitor that only does one res. but not everything that could exist, some of it is bent into the hole there. – Psycogeek Feb 13 '14 at 8:13
  • And lastly Format or Aspect. VGA monitors were originally a 4X3 aspect ratio, showing a HD pic/video on them is a 16X9, the fitment onto the screen is different. If the aspect of the picture is to be correct. The aspect is not required to be correct, but I think you can noatice that most of the resolutions selected that it displays properly are way closer to the aspect of the monitor. And you can see that aspect is trying to be maintained in the way that different resolutions are displayed. – Psycogeek Feb 13 '14 at 8:25

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