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Dual-Plan Bandwidth Smoothing for Layered-Encoded Video
Tong Gan, Kai-Kuang Ma, and Liren Zhang
IEEE Trans. Multimedia, Apr. 2005
Outline Bandwidth smoothing
Dual-plan bandwidth smoothing (DBS) scheme Trunk plan Branch plan
Simulation results
Dual-plan bandwidth smoothing scheme Based on the renegotiated constant bit rate (RCBR) service.
The reserved bandwidth limits the peak rate of the schedule. Renegotiation may fail (the reservation request for a higher ban
dwidth may be rejected by the network) Upon a renegotiation failure, the server has no choice but to pa
use the transmission. Use layered video coding to guarantee continuous video playba
ck.
L layers: one base layer and (L-1) enhancement layers. Trunk plan A L(t): deliver all L layers Branch plan Am(t): the branch plan for the mth renegotiation i
nstance rm,j: the renegotiation instances (the jth renegotiation after the
mth rate change)
Example: DBS scheme
b1
b2
b3
b4
b5Trunk plan A L(t)
r1,0r0,0 r1,1 r1,2 r2,0 r2,1 r3,0 r3,1 r4,0 r4,1 r5,0 Time, t
Cum
ula
tive d
ata
si
ze, s
Branch plan A1(t)
Branch plan A3(t)
Branch plan A4(t)
bi = ci
Example: switch plan
b1
b2
b3
Trunk plan A L(t)
r1,0r0,0 r1,1 r1,2 r2,0 r2,1 r3,0 Time, t
Cum
ula
tive d
ata
si
ze, s
b2
b3
Branch plan A1(t)
Procedure Compute the trunk plan
Adjust renegotiation instances of the trunk plan Match frame boundaries
Compute the branch plans Frame boundaries Number of layers being transmitted
Trunk plans Minimum Polyline Smoothing (MPS) a
lgorithm Renegotiation instances
Switching procedure only occurs at frame boundaries.
If the server intends to switch to a branch plan, it must completely send out all L layers of the kth frame and then follows the branch plan to transmit the (k+1)th frame.
Adjust renegotiation instance (1/2)
A L(t)
cm
Cm+1
vm kmΔ
V L(t)
mkm tr 0,
renegotiate before the rate increases
Adjust renegotiation instance (2/2)
A L(t)
cm
Cm+1
vm kmΔ
V L(t)
mkm tr 0, renegotiate after the rate decreases
Branch plans For each bandwidth increasing instance, an associ
ated branch plan should be established. Renegotiation instances
The server should switch back to the trunk plan as early as possible.
However, more renegotiations imply more overhead. Use Tr to control renegotiation frequency.
Renegotiations should only occur at frame boundary. The branch plan continues until
the end of the video, renegotiate successfully, or (the bandwidth requirement of the video) < (the current r
eserved bandwidth).
Scheme (branch plan) The server transmits an equal number of l (l
≦L) layers of each frame. The goal: maximize l Procedure:
For a given l, the corresponding constraint region is constructed.
Apply MPS algorithm to compute a temporary transmission plan.
If the plan satisfies the bandwidth constraint, it is saved as the branch plan;
otherwise, l will be decremented and the procedure is repeated.
Exploit the MPS algorithm to compute A l(t)
Vm(t)
Am(t)V l(t)
Um(t)
U l(t)
r_right
r_left (p-1)Δ (q-1)Δ
Transmit the pth frame to the (q-1)th frame during r_left ≦ t < r_right. A l(t)
Finish line
Starting point
G
Simulation C: link capacity bmin, bavg, bmax: the minimum, average, and maximu
m transmission rate of the trunk plan. Kmin = C / bmax: the number of clients admitted when
the peak-rate reservation is employed. Kavg = C / bavg: the number of clients accepted when
each one can transmit at the average rate. Kmax = C / bmin: the maximum number of concurrent
connections admitted. (base layer only)
Measurements
Network utilization Enhancement layer discarding
ratio
Video quality degradation interval
Different Tr (1/3)
In heavy load, renegotiation failures occur frequently, limiting the number of enhancement layers to be delivered.
L = 2