Haiyan Shu

An efficient arbitrary downsizing algorithm for video transcoding

When delivering video over communication networks, it is required to transcode the precoded video content to meet the demands of a broad range of end users with different bandwidths and resource constraints. One solution to transmit video over bandwidth-constrained channels is to reduce the spatial resolution of video frames and transmit a low-resolution version of the video as a tradeoff for the bit rate. In this paper, an arbitrary downsizing algorithm is proposed. This arbitrary downsizing algorithm is processed directly in the discrete cosine transform domain. Experimental results show that the proposed method can achieve a satisfactory performance. Compared to the existing methods, this algorithm is not only applicable to an intracoding frame but also to an intercoding frame. This is one of the crucial features of this method.

The realization of arbitrary downsizing video transcoding

In order to transmit the precoded bit stream through bandwidth constrained network, transcoding technique has been introduced to reduce the overall bit rate generated. Downsizing transcoding is one of the commonly used methods since it can reach very low bit rate without losing any motion information. Many efforts have been devoted to this research area. With the proposal of arbitrary downsizing, fine gradual reduction of bit rate and video quality becomes feasible. However, there is little research focusing on frame size selection for arbitrary downsizing transcoding. In this letter, the realization of arbitrary downsizing transcoding is discussed. Rate estimation scheme is applied on video sequences to choose the suitable frame size for the target bit rate. An efficient method is proposed to estimate the number of bits allocated to residue in requantization process. Experimental results show that, it can provide an accurate estimation and make a reliable decision in frame size selection.

A Resizing Algorithm With Two-Stage Realization for DCT-Based Transcoding

In video transcoding, arbitrary resizing is always desired for end users with different display capabilities. In this paper, a two-stage resizing structure is proposed for arbitrary resizing. It gives a general solution for the realization of arbitrary resizing in the transform domain. Two constraints are given for the selection of parameter set to benefit the anti-aliasing and picture quality. Illustrative examples show that our proposed two-stage resizing structure, with the qualified parameter sets, can provide an appropriate solution for arbitrary resizing

Frame-skipping transcoding with motion change consideration

Transcoding is adopted to deliver video content to a broad range of end users with different preferences and bandwidth constraints. Frame-skipping transcoding is one of the solutions to reduce the temporal resolution of the video sequence and decrease the overall bit rate. Traditionally used control scheme in frame-skipping transcoding is based on buffer constraint or considers the motion activity of each frame. In this paper, we would like to propose a new frame-skipping control scheme that considers the motion change and tries to reduce the jerky effects caused by the undesired frame skipping. Experiments show that proposed frame-skipping control scheme can produce transcoded video look more like the original one and hence remain the visual quality.

Variable frame rate transcoding considering motion information [video transcoding]

Motion information is important to consider in frame-skipping video transcoding. Traditionally methods consider only motion activity in dynamic frame skipping transcoding. In fact, motion continuity also has a distinct effect on human visual perception. In this paper, we introduce a new concept of motion change. Combined with motion activity, these two types of motion information can be used to dynamically skip frames without seriously affecting our human perception. We also propose a new frame-skipping control scheme with variable length prediction window. Experimental results show that our proposed method can present a smooth frame rate variation, and comply well with the original motion information.

Intra/Inter Macroblock Mode Decision for Error-Resilient Transcoding

When transmitting the precoded bitstream over an error-prone network, error-resilient transcoding is adopted to convert the bitstream to a resilient format for robust delivery. Intra refreshment is an efficient tool to reduce the dependency between frames and stop the channel error propagation. In the conventional scheme, the rate-distortion optimized macroblock mode decision is employed to adaptively determine the coding mode of each macroblock. However, this scheme only considers the channel error propagated from the previous frames to the current frame. As opposed to this traditional algorithm, this paper proposes a method which considers consecutive two frames in a sequence, thus taking the error propagation to the following frame into account. This enhances the overall robustness of the transcoded bitstream against the packet loss. Considering the availability of the next frame information, two cases are discussed respectively. Experimental results show that the proposed methods present quality improvement when compared with the conventional rate-distortion optimized error-resilient coding scheme under different test environments, and the PSNR improvement can reach as high as 0.9 dB.

A new scene change feature for video transcoding

In video transcoding, information collected from a precoded video stream may be used to benefit the coding process. There is a need to detect the scene change in video streams because statistical information may vary when scene change occurs. Several scene change features are discussed for compressed video. In order to realize efficient detection, we propose a novel scene change feature for compressed video streams. The motion change information within each frame is used to identify the scene change. Experimental results show that this proposed scene change feature is rather robust and can provide useful information to realize accurate detection.

Frame size selection in video downsizing transcoding application

In order to transmit a pre-coded video stream through a bandwidth constrained network, a downsizing transcoding technique has been introduced because it can reach a very low bit rate without losing any motion information. With the proposal of arbitrary downsizing, a fine gradual reduction of bit rate and video quality becomes feasible. However, there is little research focusing on frame size selection for arbitrary downsizing transcoding. In this paper, we propose an efficient method to estimate the number of bits allocated to residue information in the re-quantization process. By estimating a lower bound of the bit rate of the corresponding frame size, a reliable decision can be made. Experimental results show that the proposed method can provide an accurate estimation.

Generalized arbitrary resizing for video transcoding

In video transcoding, arbitrary resizing is always desired for end users with different display capabilities. In this paper, a two-stage resizing structure is proposed for arbitrary resizing. It gives a general solution for the realization of arbitrary resizing in the transform domain. Two constraints are given for the selection of parameter set to benefit the anti-aliasing and the picture quality. Illustrative examples show that our proposed two-stage resizing structure, with qualified parameter set, can provide a satisfactory solution for arbitrary resizing

Frame layer bit allocation for video transcoding

In order to transmit video content to different end users, a video transcoder has been adopted to re-shape the pre-coded video stream for a different purpose. In the transcoding process, the pre-coded video stream can provide useful information to improve the performance of the transcoder. The bit rates generated in the pre-coded and transcoded video streams are analyzed. Based on this analysis, a frame layer bit allocation scheme is proposed to assign a different number of bits for each frame according to the criteria that generates an output video sequence with smooth visual quality. Experimental results show that our proposed method can reduce the video quality variation.