Video transmission in wireless environments is a challenging task calling for high-compression efficiency as well as a network friendly design. Both have been major goals of the H.264/AVC standardization effort addressing "conversational" (i.e., video telephony) and "nonconversational" (i.e., storage, broadcast, or streaming) applications. The video compression performance of the H.264/AVC video coding layer typically provides a significant improvement. The network-friendly design goal of H.264/AVC is addressed via the network abstraction layer that has been developed to transport the coded video data over any existing and future networks including wireless systems. The main objective of this paper is to provide an overview over the tools which are likely to be used in wireless environments and discusses the most challenging application, wireless conversational services in greater detail. Appropriate justifications for the application of different tools based on experimental results are presented.

Abstract—We consider streaming of video sequences over both constant and variable bit-rate (VBR) channels. Our goal is to enable decoding of each video unit before exceeding its displaying deadline and, hence, to guarantee successful sequence presentation even if the media rate does not match the channel rate. In this work, we will show that the separation between a delay jitter buffer and a decoder buffer is in general suboptimal for VBR video transmitted over VBR channels. We will specify the minimum initial delay and the minimum required buffer for a given video stream and a deterministic VBR channel. In addition, we provide some probabilistic statements in case that we observe a random behavior of the channel bit rate. A specific example tailored to wireless video streaming is discussed in greater details and bounds are derived which allow guaranteeing a certain quality-of-service even for random VBR channels in a wireless environment. Simulation results validate the findings. Index Terms—Receiver buffer, streaming video, variable bit-rate (VBR), wireless video. I.

Despite the well-known challenges of variations in throughput, delay, and packet loss over the Internet, video streaming has experienced phenomenal growth, owing to the extensive research in video coding and transmission. In this paper, we review several recent advances for channel-adaptive video streaming that, we believe, will benefit the design of video streaming systems in the future. Employed in different components of the system, these techniques have the common objective of providing efficient, robust, scalable and low-latency streaming video. First, by allowing the client to control the rate at which it consumes data, adaptive media playout can be used to reduce receiver buffering and therefore average latency, and provide limited rate scalability. Secondly, rate-distortion optimized packet scheduling, a transport technique, provides a flexible framework to determine the best packet to send given the channel behaviors, the packets' deadlines, their transmission histories, the distortion reduction associated with sending each packet, and the inter-packet dependencies. Thirdly, at the source encoder channel-adaptive packet dependency control can greatly improve the error-resilience of streaming video and reduce latency. Finally we address the specific additional challenges for wireless video streaming. We consider three architectures for wireless video and discuss the utility of the reviewed techniques for each architecture.

Internet transmission is characterized by variations in throughput, delay, and packet loss, which can severely affect the quality of multimedia presentations delivered over the network. Still, Internet video streaming has experienced phenomenal growth in the last few years, owing to the extensive research in video coding and transmission. In this paper, we review several recent advances for network-adaptive video streaming that, we believe, will benefit the design of video streaming systems in the future. Employed in different system components, these techniques have the common objective of providing efficient, robust, scalable and low-latency streaming video. They range from purely server or source encoder-based techniques, through transmission schemes that could be implemented either at the sender or at the receiver, to purely client-based techniques. We discuss each of them in detail, presenting also related work and experimental results. We end the paper with a summary of the reviewed techniques and a brief discussion of future research directions.

Abstract — In this work we investigate strategies for joint radio link buffer management and scheduling for video streaming over wireless shared channels with focus on High–Speed Downlink Packet Access (HSDPA). The simulations have been carried out with the virtual mode of our wireless system emulator WiNe2. We compare different end–to–end streaming options including variations in the initial delay and timestamp–based streaming versus ahead–of–time streaming. It turns out that buffer management at the entrance to the wireless system has a similar effect as server–based rate control schemes, but avoids the need for frequent end-to-end link probing. In case of an overloaded system packets with the longest waiting time in the radio link buffer should be dropped, since most likely their presentation deadline has already expired anyway. We also conclude that hybrid scheduling strategies do not yield large gains for timestamp-based streaming, since the inherent coarse ”rate control ” is sufficient to avoid extreme unfairness in the system. In this case the use of a simple maximum–throughput scheduling policy provides best results. However, if the streaming application does not behave fair as in case of ahead–of–time streaming, the maximum–throughput policy degrades the overall system, as users with bad channel conditions are blocked. Hence, a fair scheduling algorithm provides significantly better performance. Finally, it is shown that the exploitation of simple priority information in packet headers in the dropping strategy can only increase the quality for high initial delays. I.

We consider streaming of video sequences over both, constant and variable bitrate (VBR) channels. Our goal is to enable decoding of each video unit before exceeding its displaying deadline and, hence, to guarantee successful sequence presentation even if the media rate does not match the channel rate. In this work, we will show that the separation between a delay jitter buffer and a decoder buffer is in general sub-optimal for VBR video transmitted over VBR channel. We will define the minimum initial delay and the minimum required buffer for a given video-stream and a deterministic VBR channel. In addition, we provide some probabilistic statements in the case that we have a random behaviour of the channel bit-rate. A specific example tailored to wireless video streaming is discussed in greater details and bounds are derived which allow to guarantee a certain quality-of-service even for random VBR channels in a wireless environment. Simulation results validate the findings.

Video transmission in wireless environments is a challenging task calling for high compression efficiency as well as a network friendly design. These have been major goals of the H.264/AVC standardization effort addressing "conversational" (i.e., video telephony) and "non-conversational" (i.e., storage, broadcast, or streaming) applications. The video compression performance of the H.264/AVC Video Coding Layer typically provides a significant improvement. The network-friendly design goal of H.264/AVC is addressed via the Network Abstraction Layer that has been developed to transport the coded video data over any existing and future networks including wireless systems. The main objective of this paper is to provide an overview over the tools which are likely to be used in wireless environments and discusses the most challenging application, wireless conversational services in greater detail. Appropriate justifications for the application of different tools based on experimental results are presented.