April 17, 2023 – The Contrast-aware Multiscale Banding Index (CAMBI) operates as a no-reference banding detector adding another video quality measurement tool in ClearView 9.5, newly released for NAB 2023.
Banding artifacts are artificially introduced contours arising from the quantization of a smooth region in video content. Banding is most noticeable in a medium bitrate application where the video is neither highly compressed nor provided with a substantial number of bits to faithfully represent an intensity ramp within a video frame and thus is intensified by other artifacts.
To create a banding visibility score, CAMBI extracts multiple pixel-level maps at multiple scales, for temporally sub-sampled frames of previously encoded video. It then combines these maps into a single index using properties of the human Contrast Sensitivity Function. Including CAMBI as a detection and measurement mechanism which is based on a study of the banding artifact’s dependence on multiple encoding parameters can help identify the onset of banding in video content and serve as a first step towards its mitigation.
CAMBI operates similarly to other included no-reference quality indices in ClearView 9.5 by giving a per frame score for any single video sequence that has been imported using ClearView’s comprehensive file importer, recorded from baseband inputs, or captured via its built-in IP stream input decoder. The measurement also operates as a full-reference test in a ClearView video quality analyzer such that aligned video sequences are measured together for their respective per-frame CAMBI scores with an added log entry for individual frame difference scores between source and downstream encoded/distributed versions.
CAMBI can provide a significant aid to the development of debanding features in encoders and it can provide encoder performance tests at target content transmission and delivery bit rates. Furthermore, operators and manufacturers can easily set up an encoding and transmission banding threshold test for qualification of distribution file assets with a ClearView quality analyzer. The addition of CAMBI to a ClearView video quality test routine provides the ability for comparison of CAMBI banding scores versus overall perceptual quality metrics to create content quality acceptance criteria throughout a video encoding product’s test cycle and a network operator’s content transmission delivery path.
References:
CAMBI Tech Blog
…https://netflixtechblog.com/cambi-a-banding-artifact-detector-96777ae12fe2
CAMBI Study Paper
About Video Clarity Inc.
Video Clarity Inc. provides video quality analysis systems which include quality lab applied video content recording and playback solutions for broadcasters, video-processing equipment manufacturers, and entertainment entities that must deliver high-quality video to multiple screens and continually measure the audio and video quality of their products and services. Propelled by market-leading technology, Video Clarity solutions have been adopted the worldwide by major media networks; leading broadcast-product manufacturers; and educational, government, and research organizations. Video Clarity was founded in 2003, with headquarters in Campbell, California, and distribution worldwide.
All trademarks appearing herein are the property of their respective owners.
Video Clarity Inc. Contact:
Adam Schadle, Vice President
Tel: +1 408 379 6952
Email: adams@videoclarity.com