Selection of TH is critical. Overestimation: playout rate declines giving bad playout performance. Underestimation: higher probability of having an empty buffer = playout discontinuityOptimal TH trade off rise in probability of empty buffer against increase in playout rateQueue analysis is performed and the frame arrival processes is modeled by a Poisson process. This is to simulate random networking delays, etc.Authors solve for optimal probabilities of empty buffer and frame loss probability, which is the metric for this study. Seems to be either fast or slow!!!!
When target buffer size has been reached (similar to TH in previous work) playout begins
For B_target from 50 to 200 packets in increments of 10. Higher MTBBU is good! Channel model is a two-state Markov (good or bad) . Packet loss probability is 0.05No video is used…. Everything is based on packet assumptions
Again Poisson arrival process of frames (they admit the poor choice of modelling the frame arrival rate)Makes use of variance of discontinuity (VoD)
MPR: Mean Playout RateSmall TH allows buffer overflow to take place thus losing frames
Adaptive Video PlaybackMohammed Sinky
Background Proposed concept falls under the general category of “Adaptive Media Playback or (AMP)” l 2lAMP: l ×s /f
Historical PerspectiveAdaptive Media Playout (AMP) Content Adaptive Optimal frame VDoP [Laoutaris] selection Laoutaris and Yet another AMP buffer design algorithm Video Smoothing First HD video used for evaluation Motion based AMP
Video Smoother -1996 Playout buffer (size N) Video frames playout of frames Threshold (TH) Playout rate Time controller If number of frames in playout buffer exceeds TH, maximum playout rate (m) is employed. Otherwise smoother uses proportionally reduced rates to eliminate playout pauses due to empty buffer. M. C. Yuang, S. T. Liang, Y. G. Chen, and C. L. Shen, “Dynamic video playout smoothing method formultimedia applications,” in IEEE International Conference on Communications, 1996, vol. 3, pp. 1365–1369.
Video Smoother Metrics as TH increases (l: mean frame arrival rate) p0: probability of empty buffer pL: frame loss probability
Adaptive Media Playout (AMP) - 2001 Adaptive Media Playout: the adjustment of the playout speed of the media packets depending on the condition of the channel and the current client buffer fullness. Video playout based on channel conditions: Bad conditions: slow down playout, virtual increase in buffer Good conditions: following recovery of bad conditions, playout is done faster than normal E. Steinbach, N. Farber, and B. Girod, “Adaptive playout for low latency video streaming,” in ImageProcessing, 2001. Proceedings. 2001 International Conference on, 2001, vol. 1, pp. 962–965.
AMP Assumptions: Audio+Video frame fit into one packet Lost packets: retransmission requests are sent from client to server (application layer)
AMP Packet burst error and the arrival of retransmissions If a packet burst loss exceeds the maximum playout time, we get buffer underflow: freeze video
AMP Two main criteria for evaluation Probability of buffer underflow Average value of max burst length: Average end-to-end delay introduced by adaptive playout
AMP Metric: Mean Time Between Buffer Underflow (MTBBU) s: slowdown factor (s≥1) f: speed-up factor (f≤1)
Variance of Distortion of Playout(VDoP) - 2001 New metric to gage interruptions in video playback Extension of 1996 work done by Yuang which suffered from an undesirable fast forward effect N. Laoutaris and I. Stavrakakis, “Adaptive playout strategies for packet video receivers with finite buffercapacity,” in Communications, 2001. ICC 2001. IEEE International Conference on, 2001, vol. 3, pp. 969–973.
Recent Take into consideration motion characteristics of frames Choosing specific frames (frame selection) Most work revolves around finding the optimum buffer size, threshold and corresponding frame rate adjustment in the context of AMP
Many of the works consider the network to be a cloud (possibly internet, LAN, etc.) We consider specific home network, ad hoc, 802.11 based Most deal with frames as a whole, and don’t get into details of packetization We are relying on frames split across packets Assumptions are made on frame arrival rates In our scenario a more accurate estimation of frame arrival rates can be considered HD video is not considered Our work is centralized around HD video