Darrell L. Young

Loss of Interpretability due to Compression Effects as Measured by the New Video NIIRS

The effect of video compression is examined using the task-based performance metrics of the new Video National Intelligence Interpretability Rating Scale (Video NIIRS). Video NIIRS is a subjective task criteria scale similar to the well-known Visible NIIRS used for still image quality measurement. However, each task in the Video NIIRS includes a dynamic component that requires video of sufficient spatial and temporal resolution. The loss of Video NIIRS due to compression is experimentally measured for select cases. The results show that an increase in the compression and an associated increase in artifacts reduces task based interpretability and lowers the Video-NIIRS rating of the video clips. The extent of the effect has implications for system design.

Factors Related to Low Slant Angle Affecting Airborne Video Interpretability

The following material is given to address the effect of low slant angle on video interpretability: 1) an equation for the minimum slant angle as a function of field-of-view to prevent no more than a &sqrt2; change in GSD across the scene; 2) evidence for reduced situational awareness due to errors in perceived depth at low slant angle converting to position errors; 3) an equation for optimum slant angle and target orientation with respect to maximizing exposed target area; 4) the impact of the increased probability of occlusion as a function of slant angle; 5) a derivation for the loss of resolution due to atmospheric turbulence and scattering. In addition, modifications to Video-NIIRS for low slant angle are suggested. The recommended modifications for low-slant angle Video-NIIRS are: 1) to rate at or near the center of the scene; and 2) include target orientations in the Video-NIIRS criteria.

Color in perceptual tracking using low frame rate motion imagery

A perceptual evaluation compared tracking performance when using color versus panchromatic synthetic imagery at low frame rates. Frame rate was found to have an effect on tracking performance for the panchromatic motion imagery. Color was found to be associated with improved tracking performance at 2 frames per second (FPS), but not at 6 FPS or greater. A self estimate of task confidence given by the respondents was found to be correlated to the measured tracking performance, which supports the use of task confidence as a proxy for task performance in the future development and validation of a motion imagery rating scale.

When to engage video resilience options

Video bit errors or missing packets can result in freezing or distortion causing a severe loss of interpretability. Resilience options can mitigate the error propagation that occurs due to the spatial and temporal dependencies in the compressed bit stream. Resilience options can be invoked at the encoder, based on feedback from the application layer decoder. If no feedback channel is available, the encoder controller can estimate data link performance and engage sufficient resilience options. Decode errors can be summarized in metadata to alert upstream encoders to engage resilience and downstream consumers of artifacts due to damaged or missing macro blocks.