Abstract In this paper we present an adaptive video transmission framework that integrates rate allocation and buffer control at the source with the playback adjustment mechanism at the receiver. A transmission rate is determined by a rate allocation algorithm which uses the program clock reference (PCR) embedded in the video streams to regulate the transmission rate in a refined way. The server side also maintains multiple buffers for packets of different importance levels to trade off random loss for controlled loss according to the source buffer size, the visual impact, and the playback deadline. An over-boundary playback adjustment mechanism based on proportional-integra (PI) controller is adopted at the receiver to maximize the visual quality of the displayed video according to the overall loss and the receiver buffer occupancy. The performance of our proposed framework is evaluated in terms of peak signal-to-noise ratio (PSNR) in the simulations, and the simulation results demonstrate the improvement of the average PSNR values as well as the better quality of the decoded frames. Key words Variable-bit-rate (VBR), video streaming, program clock reference (PCR), buffer management, proportional-integra controller In order to obtain better visual quality, videos are required to use variable-bit-rate (VBR) encoding. However, it is more difficult to manage the VBR video traffic because of its significant bit-rate burstiness [1] . Normally, transmission of video requires high bandwidth and low delay. Many researches have been done on VBR compressed video transmission [2−9] . In [2], the problem of streaming packetized media in a rate-distortion optimized way was addressed. An interactive descent algorithm was used to minimize the average end-to-end distortion. However, the high computational complexity of this approach made it less appealing during real-time streaming, where the server must adapt to bandwidth variations very quickly. Adaptive media playout (AMP) was proposed from the receiver point of view in [3] to vary the playout rate of media frames according to the buffer occupancy as soon as the target buffer level is reached, which may cause jitter at the critical point of two adjacent buffer levels. A multi-buffer scheduling scheme was proposed in [4] to schedule the transmission based on the source buffer priority. A proportional-integralderivative (PID) controller was adopted in [5] to have better tradeoff between spatial and temporal qualities. The above two schemes belong to server-side technologies, which only consider the sender buffer state without taking into account the end-to-end delay constraint of multimedia applications. [6] addressed the problem of optimizing the playback delay experienced by a population of heterogeneous clients and proposed a server-based scheduling strategy that targets a fair distribution of the playback delays. [7] modeled the streaming system as a queuing system. An optimal substream was selected based on the decoding failure probability of the frame and the effective network bandwidth. [8] proposed a reverse frame selection (RFS) scheme based on dynamic programming to solve the problem of video streaming over VBR channels. [9] presented a streaming framework centered around the concept of priority drop. It combined the scalable compression and adaptive streaming to provide a graceful degradation of the quality. Most of the previous approaches focused on regulating transmission rate through the observation of network sta-
In REF , the rate allocation algorithm, performed at the Group of Picture (GoP) level, is in charge of determining the transmission rate from the buffers and a playback adjustment mechanism.
Joint Rate Allocation and Buffer Management for Robust Transmission of VBR Video
ICMCS
Computer Science