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Biamp Systems

Aspect ratio mismatches

TesiraLUX supports a wide range of video formats with the highest quality supported mode being 4K60 UHD. Many laptop and desktop computers are not able to display 4K60 and will display the video using a lower resolution or refresh rate modes. In some instances, this may result in an aspect ratio mismatch with the display devices. TesiraLUX will always strive to maintain the aspect ratio of the source image to prevent geometric stretching or distortion on the output device. This will result in letterboxing or pillarboxing bars on the output image if the aspect ratios are not the same between the input source and output sink. 

Example: A laptop connected to a TesiraLUX IDH-1 encoder is transmitting 1920x1200 (16:10 ratio) because it is not capable of any higher resolutions. The sink device connected to the TesiraLUX OH-1 decoder is a 16:9 4K UHD monitor. Rather than distort the aspect ratio of the 16:10 source image, TesiraLUX will add black bars on the sides of the output image (pillarboxing). This can be corrected if the laptop output is configured to a 16:9 aspect ratio resolution mode, such as 1920x1080.

Changing Source Resolution

In Windows, the first place most people would go to change the output resolution of a computer is in the Display control panel. The advanced display settings changes the resolution of the desktop rendering. However, this does not always change the HDMI or DP output resolution mode, which results in an apparent discrepancy with the input resolution detected by TesiraLUX. In this case, the computer will need to have the output mode forced to match the desired desktop resolution. It is preferable to select a display resolution that correlates to the aspect ratio of display devices attached to TesiraLUX OH-1 decoders. The output mode of the computer can be forced via the "List All Modes" option of the Display Adapter properties or via the graphics card's control panel, such as the Intel HD Graphics Control Panel. 

Depending on the supported modes of the display device, it is possible to force an output format via the AV Output block which matches the aspect ratio of the source image. The connected display would internally handle scaling. This likely will result in geometric distortions to the image, such as stretching. It is instead preferred to match the source aspect ratio without having to use any ratio scaling as this would avoid any boxing on the display output.

Intel HD Graphics Control Panel

If changing the resolution from the Display control panel in Windows doesn't change the output resolution of the HDMI or DP video connection, the display mode needs to be changed to "Maintain Display Scaling". The screenshot below shows how to do this for computers equipped with Intel Graphics:

IntelHDGraphics.PNG

Other scaling modes will result in the desired desktop resolution being upscaled or stretched to the negotiated input mode of the TesiraLUX IDH-1 encoder, which may result in aspect ratio mismatches or geometric distortions. Changing the Intel Graphics scaling to Maintain Display Scaling will prevent any disparity between the desktop resolution and the output mode of the graphics port. If pillarboxing or letterboxing is not desired, a resolution should be selected which matches the aspect ratio of the display devices connected to TesiraLUX OH-1 decoders.

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