Flicker effects in adaptive video streaming to handheld devices

Abstract

Streaming video over the Internet requires mechanisms that limit the streams' bandwidth consumption within its fair share. TCP streaming guarantees this and provides lossless streaming as a side-effect. Adaptation by packet drop does not occur in the network, and excessive startup latency and stalling must be prevented by adapting the bandwidth consumption of the video itself. However, when the adaptation is performed during an ongoing session, it may influence the perceived quality of the entire video and result in improved or reduced visual quality of experience. We have investigated visual artifacts that are caused by adaptive layer switching -we call them flicker effects -and present our results for handheld devices in this paper.We considered three types of flicker, namely noise, blur and motion flicker. The perceptual impact of flicker is explored through subjective assessments. We vary both the intensity of quality changes (amplitude) and the number of quality changes per second (frequency). Users' ability to detect and their acceptance of variations in the amplitudes and frequencies of the quality changes are explored across four content types. Our results indicate that multiple factors influence the acceptance of different quality variations. Amplitude plays the dominant role in delivering satisfactory video quality, while frequency can also be adjusted to relieve the annoyance of flicker artifacts.

Quality of Experience of adaptive video streaming: Investigation in service parameters and subjective quality assessment methodology

“…Following the recommendation of [3], the compression domain was considered as the switching dimension. For each SRC, four quality levels were produced using Rhozet Carbon Coder with the setting summarized in Table 2.…”

“…In the same time, the study presented in [3] indicates that if the duration spent on the high quality level is sufficiently long, higher switching frequencies do not significantly degrade the QoE. Considering the switching amplitude, most of the previous studies [3][4][5][6][7] conclude that gradual multiple variations are preferred over rapid variations. Nevertheless, as highlighted in [4], this conclusion may not be applied to the scenarios where the quality levels' difference is very small.…”

“…About the switching frequency, results presented in [2][3][4][5][6] show that frequency of the adaptation should be kept as low as possible. In the same time, the study presented in [3] indicates that if the duration spent on the high quality level is sufficiently long, higher switching frequencies do not significantly degrade the QoE.…”

“…Studied presented in [3,8] revealed that the effect of spatial and temporal switching varies depending on the content type. This was found to be even true for switches with the same amplitude so that it is difficult to spot quality oscillation when there are frequent scene changes while in steady shots they are more noticeable.…”

A Real-Time Adaptive Algorithm for Video Streaming over Multiple Wireless Access Networks

“…For instance, according to [25], the layer variations will decrease the users' watching experience, and thus the number of layer variations was used to reflect the smoothness in our experiments. The performance metrics used in our experiments are listed as follows:…”