Streaming stored video:revisited constant bit rate video client video constant bit transmission reception[ rate video anle]nwno playout at client variable network delay client playout time delay client-side buffering and playout delay:compensate for network-added delay,delay jitter Multimedia Networking 9-11
constant bit rate video transmission time variable network delay client video reception constant bit rate video playout at client client playout delay buffered video ▪ client-side buffering and playout delay: compensate for network-added delay, delay jitter Streaming stored video: revisited Multimedia Networking 9-11
Client-side buffering,playout buffer fill level, ←Q(0→ variable fill playout rate. rate,x(t) e.g.,CBR r video server client application ←—buffer,size B+ client Multimedia Networking 9-12
Client-side buffering, playout variable fill rate, x(t) client application buffer, size B playout rate, e.g., CBR r buffer fill level, Q(t) video server client Multimedia Networking 9-12
Client-side buffering,playout buffer fill level. ←Q(0+ variable fill playout rate, rate,x《t) e.g.,CBR r video server client application ←一buffer,size B→ client I.Initial fill of buffer until playout begins at tp 2.playout begins at tp. 3.buffer fill level varies over time as fill rate x(t)varies and playout rate r is constant Multimedia Networking 9-13
Client-side buffering, playout variable fill rate, x(t) client application buffer, size B playout rate, e.g., CBR r buffer fill level, Q(t) video server client 1. Initial fill of buffer until playout begins at tp 2. playout begins at tp, 3. buffer fill level varies over time as fill rate x(t) varies and playout rate r is constant Multimedia Networking 9-13
Client-side buffering,playout buffer fill level, ←Q(0→ variable fill playout rate rate,x(t) e.g.,CBR r video server client application ←—buffer,,size B→ playout buffering:average fill rate (x),playout rate (r): x<r:buffer eventually empties(causing freezing of video playout until buffer again fills) x>r:buffer will not empty,provided initial playout delay is large enough to absorb variability in x(t) initial playout delay tradeoff:buffer starvation less likely with larger delay,but larger delay until user begins watching Multimedia Networking 9-14
playout buffering: average fill rate (x), playout rate (r): ▪ x < r: buffer eventually empties (causing freezing of video playout until buffer again fills) ▪ x > r: buffer will not empty, provided initial playout delay is large enough to absorb variability in x(t) • initial playout delay tradeoff: buffer starvation less likely with larger delay, but larger delay until user begins watching variable fill rate, x(t) client application buffer, size B playout rate, e.g., CBR r buffer fill level, Q(t) video server Client-side buffering, playout Multimedia Networking 9-14
Streaming multimedia:UDP server sends at rate appropriate for client often:send rate encoding rate constant rate transmission rate can be oblivious to congestion levels short playout delay(2-5 seconds)to remove network jitter error recovery:application-level,time permitting RTP [RFC 2326]:multimedia payload types UDP may not go through firewalls Multimedia Networking 9-15
Streaming multimedia: UDP ▪ server sends at rate appropriate for client • often: send rate = encoding rate = constant rate • transmission rate can be oblivious to congestion levels ▪ short playout delay (2-5 seconds) to remove network jitter ▪ error recovery: application-level, time permitting ▪ RTP [RFC 2326]: multimedia payload types ▪ UDP may not go through firewalls Multimedia Networking 9-15