Camera Video Display Problems Tested

By Ethan Ace, Published Mar 18, 2016, 12:00am EDT (Research)

In the old days, displaying video was simple. Both cameras are monitors were generally the same aspect ratio, so it was fairly simple to display video without any problems.

Now, though, with various aspect ratios (16:9 monitors, 4:3 cameras, 16:9 cameras, fisheye streams, multi-imagers, etc.), this is becoming much more difficult.

Indeed, many VMS clients are now defaulting to cropping or warping video by default.

In this report, we look at this problem and share examples of how Axis, Dahua and Hikvision do this.

Cropping Problem

There are two key problems here, cropping and stretching.

Compare the two images below, notice how when it 'fills' the pane, the top and bottom are cropped:

This animation below shows it in action.

Stretching Problem

Compare the two images below, the narrower one is a 16:9 aspect ratio camera but the VMS displays it wider / stretched:

In the comparison below, you can see how the VMS is stretching:

Hikvision

Hikvision has little regard for proper aspect ratio. By default, Hikvision cameras, DVRs/NVRs, and iVMS-4200 CMS all stretch video to the window, regardless of aspect ratio. The entire image is visible (unlike Axis, below, which crops parts of the image), but distorted in most cases.

This can be changed to respect aspect ratio, but the option is buried in settings (Tool > System Configuration > Image > View Scale > Original Resolution). The image below shows the same cameras as above, all 16:9, in their proper aspect.

Axis Camera Station

In our Axis Camera Station 5 test, cameras are set to "fill" the view by default. This essentially means that the horizontal width of the image is fit to the width of the viewing pane. However, areas at the top and bottom of the FOV are cut off.

This can be changed in configuration to fit the full image in the pane, which displays the full FOV, but results in varying levels of blank space to either side, seen below. However, using this option, at least the full FOV is visible and aspect ratio is respected.

Dahua

In Dahua web interfaces, aspect ratio is not respected, although client software defaults to "original aspect ratio", with options to stretch to fill. This can result in extreme stretching depending on the window aspect ratio and size.

For example, the screenshot below was taken from the web interface of a Dahua 4K model. Regardless of the window height, video is still stretched to fill the width by default, resulting in squashed or stretched video. There are controls to show video in the original aspect, but they are not well labeled and may users may not realize they are even there.

The Solution

Client views will rarely be perfectly filled, for two reasons:

  1. Monitors are 16:9, but some cameras are not: Though many would like to proclaim HD and 16:9 formats as the way to go, 4:3 models are still commonly used (and arguably provide more useful images), including 3 MP, 5 MP, and now 12 MP resolutions. It will be years before 4:3 is no longer available.
  2. UI elements take up space: Toolbars, Windows and Mac task bars, event lists, and other UI elements take up screen space, meaning even if the VMS client is run full screen on a 16:9 monitor with 16:9 cameras in a split view, these controls may take up space and skew the aspect ratio of viewing windows.

Simply put, the solution is to stop distorting camera aspect ratio. Though some may consider full viewing windows "prettier", they ultimately detract from system usability due to the issues above. Blank space between panes is a better solution than viewing distorted video.

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