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MV Sensor Crop

Overview 

Sensor Crop is a new feature for the MV12 that allows for configuring a fixed zoom and pan without any loss in image quality.

 

sensor_crop_config.gif

 

In the above gif, the camera is streaming at 1080p full-frame (4MP sensor downsampled to 1080p). After selecting a crop region and applying, the output from the sensor is cropped to the selected region at full 1080P. This produces a higher quality, zoomed image for the selected region.

Use Case 

  • Sensor crop is best utilized on cameras where physical/logistical limitations of the camera installation location relative to the area of interest prevent:

    • viewing a selection of the frame in greater detail

    • removing portions of the perimeter of the frame that are undesirable

  • Some examples might include:

    • Identification: viewing persons entering a building entryway in greater detail for better identification
    • Privacy: removing a portion of the frame that observes a private work desk/area

    • Analytics: removing a portion of the frame that observes passersby outside a glass window

Configuration 

To configure Sensor crop on a MV12:

  • click the "Select crop region" button
  • move and/or resize the selection pane to the desired crop region
  • click "Apply crop region" to apply this setting
Before applying sensor crop:

sensor_crop_before.png

 

The crop region can also be moved anywhere in the frame, and can also be scaled; it doesn't need to be exactly 720p or 1080p.

If a crop region is selected that is larger than the video quality setting (720p or 1080p), the camera first crops the frame and then downscales to the desired resolution.

After applying sensor crop:
sensor_crop_after.png
 
It takes a few moments for the settings to change on the camera. Once the crop is applied, all footage will be recorded with this new view.
 
After applying the change, we can see the region within the frame has been correctly cropped. The Sensor crop "Apply crop region" button has been replaced with a representation of the current crop region. A "Reset crop region" button is now presented in the event the region needs to be reset/reconfigured.
 
Note: The High dynamic range and Sensor crop features cannot be enabled at the same time. Enabling one of these features will disable the ability to configure the other.

Sensor Crop vs. Optical Zoom vs. Digital Zoom 

Sensor crop is different from optical and digital zooming. To briefly compare:

  • Sensor crop

    • Changes applied after optics but before sampling/storing of footage to enlarge a desired region

    • Crops the sensor to a selected region before capturing a frame and downsampling (if required)

    • Requires no moving parts

  • Optical Zoom

    • Changes applied to optics to enlarge a desired region

    • Alters the focal length/aperture/etc when capturing footage

    • Requires moving parts

  • Digital Zoom
    • Applied after optics and sampling/storing of footage to enlarge a desired region
    • Upsamples the footage in software and may require additional processing for pixel inferences
    • Requires no moving parts

Technical Breakdown 

How It Works

With Sensor Crop, there is no pixelation because the image is never upscaled.
The MV12's sensor captures raw video at 4 megapixels (2688x1520). This is then scaled down to 1080p or 720p before saving to local storage.
 
The difference between these frame sizes is illustrated below:
 



Instead of simply scaling the whole frame down to our desired resolution, we can crop the image first. The result is a zoomed image of up to 2.1x (720p) or 1.4x (1080p).

There's no loss of quality because we're not scaling up and inferring the values of pixels. They're all read directly from the sensor.
 
sensor_crop_more_info_link.png
 
The "more information" link reveals a modal which explains how the feature works.
sensor_crop_more_info.png

Event Log 

sensor_crop_event_log_entry.png

Image settings change 

Details include:

  • user: user who executed the change
  • before: sensor crop settings prior to application of change
  • after: sensor crop settings after change
    • if value remains unchanged between before/after, this value is not represented

Expected values:

  • user: user's admin email address
  • x: horizontal pixel start [off-set calculated from top-left corner of sensor]
    • min. 0, max. 1408 for 720p video quality setting
    • min. 0, max. 768 for 1080p video quality setting
  • y: vertical pixel start [off-set calculated from top-left corner of sensor]
    • min. 0, max. 792 for 720p video quality setting
    • min. 0, max. 432 for 1080p video quality setting
  • w: width in pixels
    • -1 for full sensor width
    • 1280 default minimum for 720p video quality setting
    • 1920 default minimum for 1080p video quality setting
  • h: height in pixels
    • -1 for full sensor height
    • 720 default minimum for 720p video quality
    • 1080 default minimum for 1080p video quality setting

FAQ

Is this the same as Digital Zoom? 

No. Digital zoom has negative connotations, as it usually means scaling an image up. If you want to turn a 100x100 pixel image into a 200x200 pixel image, 75% of the information in that picture must be inferred from the original pixels; this means severe pixelation.
bunny_zoomies.png
This does not apply to Sensor Crop. With Sensor Crop, there is no pixelation because the image is never upscaled.

Can I still see the cropped region in historical footage after applying sensor crop? 

No. When applying sensor crop, you are telling the sensor to discard any information outside of the selected region.

 

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