Multi-Clip Video Editing from a Single Viewpoint

International audienceWe propose a framework for automatically generating multiple clips suitable for video editing by simulating pan-tilt-zoom camera movements within the frame of a single static camera. Assuming important actors and objects can be localized using computer vision techniques, our method requires only minimal user input to define the subject matter of each sub-clip. The composition of each sub-clip is automatically computed in a novel L1-norm optimization framework. Our approach encodes several common cinematographic practices into a single convex cost function minimization problem, resulting in aesthetically pleasing sub-clips which can easily be edited together using off-the-shelf multi-clip video editing software. We demonstrate our approach on five video sequences of a live theatre performance by generating multiple synchronized subclips for each sequence

Intraframe Prediction with Intraframe Update Step for Motion-Compensated Lifted Wavelet Video Coding

Abstract. In motion-compensated lifted wavelet video coding, the calculation of the highpass frame involves interframe prediction. Due to occlusions, or change of intensity, or new objects in the video frame, interframe prediction is not always effective. Intraframe prediction provides an alternative and increases coding efficiency. However, previous analysis shows that these intraframe predicted pixels suffer higher distortion propagation than the rest of the pixels in the open-loop scheme. The main contribution of this paper is to mitigate this increased distortion through an intraframe update step. We propose a perfectly invertible sequence of operations. In addition, we present theoretical analysis of the reduction in distortion due to the inclusion of the proposed intraframe update step for various intraframe prediction modes. This is compared with practical measurements. Index Terms lifted wavelet, intra prediction, update step

Distortion Prediction For Motion-Compensated Lifted Haar Wavelet Transform and its application to Rate Allocation

In this paper we present a solution for low complexity rate allocation for video compression using motioncompensated lifted wavelet transform. We assume that after temporal decomposition a standard still image coding scheme like JPEG2000 is used to encode the resulting temporal bandpass frames. We show that the reconstruction distortion of a group of pictures can be accurately predicted from the distortion introduced into the temporally decomposed frames despite the nonorthonormality of the transform. We model the operational rate-distortion function of the still image coding using a simple parametric model and solve the rate allocation problem by minimizing a Lagrangian cost function. We compare our rate-allocation approach with a heuristic scheme and observe significant improvements in terms of rate-distortion performance at dramatically reduced computational complexity. The gains are particularly significant if the motion field is represented with sub-pel accuracy. 1

MULTIPLE DESCRIPTION VIDEO CODING USING MOTION-COMPENSATED LIFTED 3D WAVELET DECOMPOSITION

In this paper we design a multiple description (MD) video coding scheme based on the motion compensated (MC) lifted wavelet transform. A major advantage of basing MD video coding on motion-compensated lifted 3D wavelet decomposition is that it does not require any mismatch control like in a hybrid codec which was previously achieved by sending drift compensation data. We propose to perform the temporal decomposition of a group of pictures and then create multiple descriptions for each temporally transformed frame. We use polyphase sub-sampling with an appropriate amount of oversampling to form the descriptions and to control the redundancy among them. We determine the appropriate amount of redundancy as a function of description loss probability. Our experimental results show that the controlled introduction of redundancy leads to significant improvements in lossy transmission environments. 1