Variable frame rate control jerkiness-driven

Abstract

We are introducing a real-time variable frame rate control scheme capable of optimizing both spatial and temporal video qualities. It traces the motion of incoming video frames and automatically tunes the outgoing frame rate according to the level of jerkiness acceptable by the user. The control scheme was conceived within the framework of mobile communications, which require an optimum use of both the available bandwidth and terminal resources. We have designed and implemented a video transcoding architecture which supports our frame rate control. The transcoder has been developed at the Coritel laboratories, Rome, Italy (Coritel is a research consortium managed by Ericsson Lab, Italy, and the University of Rome La Sapienza), while the visual tests were carried out at the ISCOM laboratory, Italian Communication Ministry, Rome, Italy. The proposed transcoding architecture is compatible with the constraints of real-time communications and it has been extensively tested under a wide range of conditions. We then present a subjective assessment of our solution carried out in a fully equipped professional laboratory. Within this assessment a number of non-expert viewers were asked to express their preference when watching side by side the same video, coded at a variable frame rate and at a fixed frame rate. Results show that in most cases a variable frame rate control based on a dynamic bit/frame allocation scheme might substantially improve video quality perceived by viewers.