Upload
others
View
9
Download
0
Embed Size (px)
Citation preview
Rebera: Real-time Bandwidth Estimation andRate Adaptation for Video Calls
over Cellular Networks
E. Kurdoglu, Y. Liu, Y. Wang 1
Y. Shi, C. Gu, J. Lyu 2
1NYU Tandon School of Engineering
2Tencent Co. Ltd.
May 11, 2016
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Outline
1 Introduction and Problem Setting
2 Rebera ComponentsMeasuring the Current BandwidthPredicting the Future BandwidthDetermining the Sending Rate (Bit-budget)Encoder & Video Stream StructureDynamic Frame Selection
3 Experiment Results
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Video calls: very low-delay, interactive applications
1 Need to adapt transmission rate wrt network speed:Tx rate > Bandwidth ⇒ intolerable delaysTx rate < Bandwidth ⇒ under-utilized link
Accurate measurement and forecast of bandwidth is hard!
2 Need to adapt video encoding rate wrt to network speed
Accurate low-delay video rate control is hard!
3 Need resiliency against late or lost packets
Cellular links can be highly volatile: link speeds, delays...
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
A Video Call Scenario
ISP1 Internet ISP2
S D
BS BD
Challenge: measuring and predicting the e2e bandwidth
Assume: cellular links are the only bottlenecks
Model: cellular links as isolated queues (no cross-traffic)
uplink buffer in the device, downlink buffer in the BS
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Outline
1 Introduction and Problem Setting
2 Rebera ComponentsMeasuring the Current BandwidthPredicting the Future BandwidthDetermining the Sending Rate (Bit-budget)Encoder & Video Stream StructureDynamic Frame Selection
3 Experiment Results
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Rebera Overview
PacketTransmission
H.264/AVCHierP
CapacityPrediction
PacketReception
CapacityMeasurement
Decode &Display
sender
receiver
We periodically insert I-frames
Intra-period: time between two successive I-frames (≈1 sec)
Rate control performed at the beginning of each intra-period
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Measuring the Current Bandwidth
Observation: We can measure bandwidth by sending packet trainsand measuring packet inter-arrival times at the receiver.
…
a2 a3 ap
z2
z3
zp
time⇒ mn ,
z2 + · · ·+ zpa2 + · · ·+ ap
,Zn
An
Key idea: Use the packets belonging to a frame as a packet train.
1 Estimate avg. ABW in thelast intra-period
2 Feed it back to sender
3 Slide the window
ZK
AK
Z1
A1
now
sliding window
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Predicting the Future Bandwidth
Observation: Bandwidth measurement values are correlated.
Key idea: Forecast future bandwidth from past values with onlinelinear adaptive filtering (e.g. RLS)
time(sec)200 250 300 350 400 450 500
kbps
0
500
1000
1500MeasurementPrediction (RLS)
ck+1 =M−1∑i=0
wi (k)ck−i
M number of filter tapsw(k) filter tap vector of length Mck measured capacity
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Determining the Sending Rate (≡ Bit-budget)
Observation: Forecast errors are inevitable.
Key idea: Estimate the (almost) worst-case scenario to find the(almost) safest max sending rate.
rk sending rateεk exact-to-predicted ratio (= ck
ck)
qk backlogged bits
Pr(rk+1 > ck+1) ≤ δ ⇒ Pr
(εk+1 <
rk+1
ck+1
)≤ δ
r safek+1 = ck+1 × δ-quantile of ε
Bit-budget for intra-period k + 1
bk+1 = r safek+1 × T − qk
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Determining the Sending Rate (≡ Bit-budget)
Observation: Forecast errors are inevitable.
Key idea: Estimate the (almost) worst-case scenario to find the(almost) safest max sending rate.
rk sending rateεk exact-to-predicted ratio (= ck
ck)
qk backlogged bits
Pr(rk+1 > ck+1) ≤ δ ⇒ Pr
(εk+1 <
rk+1
ck+1
)≤ δ
r safek+1 = ck+1 × δ-quantile of ε
Bit-budget for intra-period k + 1
bk+1 = r safek+1 × T − qk
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Encoder & Video Stream Structure
Observation: Resiliency against packet losses is essential.
Key idea: Use hierarchical-P temporal layering.
GoP GoP
I0
P1
P2
P3
P4
P5 P7
I8P6
time
Intra-period1 Enables UEP X
2 Complexity & overheadkept minimum X
3 DFS does not causejitter. X
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Dynamic Frame Selection for Hierarchical-P Video
Observation: When video rate > target bitrate, we can discardhigher layer frames and maintain a stable frame rate.
Requirement: Must make the “send/discard” decision on the fly.
Decision for frame P1?
Cannot wait for {P2,P4,P6}
GoP GoP
I0
P1
P2
P3
P4
P5 P7
I8P6
time
Intra-period
Sequential decision makingalgorithm considers:
1 Qualities of layers
2 Decoding dependencies
3 Smoothness of frameintervals
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Outline
1 Introduction and Problem Setting
2 Rebera ComponentsMeasuring the Current BandwidthPredicting the Future BandwidthDetermining the Sending Rate (Bit-budget)Encoder & Video Stream StructureDynamic Frame Selection
3 Experiment Results
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Our Testbed
NYU Network
S D
CS CD
eth0eth1
eth0eth1
Implemented in C++ (platform: Linux)Encoder: x264, modified to generate hierarchical-P w/ 3 TLsDecoder: FFmpegCellular links emulated by CellSim
FaceTime used as a benchmark
Performance metrics: ABW utilization, 95-percentile packet &frame delays
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Evaluation under Cellular Bandwidth Traces
0 200 400 600 800 1000
Mbps
0
0.5 Tr1
0 200 400 600 800 1000
Mbps
0
0.5 Tr2
0 200 400 600 800 1000
Mbps
0
1 Tr3
0 200 400 600 800 1000
Mbps
012 Tr4
0 200 400 600 800 1000
Mbps
0
2Tr5
time (sec)0 200 400 600 800 1000
Mbps
0
2Tr6
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Evaluation under Cellular Bandwidth Traces
ABW utilization percentage10 20 30 40 50 60 70
95
-pe
rce
ntile
fra
me
de
lays (
mse
c)
0
1000
2000
3000
4000
5000
6000
A-BA-C B-A
B-CC-A
C-B
att-tmobile
att-verizon3g
att-verizon4g
tmobile-att
tmobile-verizon3g
tmobile-verizon4g
verizon3g-att
verizon3g-tmobile
verizon4g-att
verizon4g-tmobile
A-BA-CB-A
B-C
C-A
C-B
att-tmobile
att-verizon3g att-verizon4g
tmobile-att
tmobile-verizon3g
tmobile-verizon4g
verizon3g-att
verizon3g-tmobile
verizon4g-att
verizon4g-tmobile
Double-link scenarios
FaceTimeRebera
Rebera avg. util.: 55%, avg. 95-percentile frame delay: 865 msecFaceTime avg. util.: 32%, avg. 95-percentile frame delay: 2.8 sec
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Evaluation under Cellular Bandwidth Traces
ABW utilization percentage10 20 30 40 50 60 70
me
an
fra
me
de
lays (
mse
c)
0
200
400
600
800
1000
1200
1400
1600
1800
A-B
A-C
B-A
B-C C-AC-B
att-tmobile
att-verizon3g
att-verizon4g
tmobile-att
tmobile-verizon3g
tmobile-verizon4g
verizon3g-att
verizon3g-tmobile
verizon4g-att
verizon4g-tmobile
A-BA-C
B-A B-C
C-A
C-B
att-tmobileatt-verizon3g
att-verizon4gtmobile-att
tmobile-verizon3g
tmobile-verizon4g
verizon3g-att
verizon3g-tmobile
verizon4g-attverizon4g-tmobile
Double-link scenarios
FaceTimeRebera
Rebera avg. util.: 55%, avg. mean frame delay: 295 msecFaceTime avg. util.: 32%, avg. mean frame delay: 620 msec
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Evaluation under Cellular Bandwidth Traces
sec0 100 200 300 400 500 600 700 800
kbps
0
500
1000
1500
2000verizon3g-att
CapacityFaceTimeRebera
sec0 100 200 300 400 500 600 700 800 900 1000
kbps
0
500
1000
1500
2000verizon3g-tmobile
CapacityFaceTimeRebera
sec0 100 200 300 400 500 600 700 800
kbps
0
500
1000
1500
2000att-verizon4g
CapacityFaceTimeRebera
sec0 100 200 300 400 500 600 700 800
kbps
0
500
1000
1500
2000tmobile-att
CapacityFaceTimeRebera
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Conclusions
Proposed a real-time bandwidth estimation for video calls→ can be integrated with existing CC mechanisms
Sequential linear prediction allows forecasting→ can be further improved: ML, etc...
Hierarchical-P structure enables easy rate control and someresiliency
Proposed method integrated into last version of WeChat
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks
Thanks!
Find the code and reproduce our work at
http://vision.poly.edu/
Q&A
Kurdoglu, Liu, Wang, Shi, Gu, Lyu NYU Tandon School of Engineering, Tencent Co. Ltd.
Rebera: Real-time Bandwidth Estimation and Rate Adaptation for Video Calls over Cellular Networks