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WISH: User-centric Bitrate Adaptation for HTTP Adaptive Streaming on Mobile Devices



Recently, mobile devices have become paramount in online video streaming. Adaptive bitrate (ABR) algorithms of players responsible for selecting the quality of the videos face critical challenges in providing a high Quality of Experience (QoE) for end users. One open issue is how to ensure the optimal experience for heterogeneous devices in the context of extreme variation of mobile broadband networks. Additionally, end users may have different priorities on video quality and data usage (i.e., the amount of data downloaded to the devices through the mobile networks). A generic mechanism for players that enables specification of various policies to meet end users' needs is still missing. In this paper, we propose a weighted sum model, namely WISH, that yields high QoE of the video and allows end users to express their preferences among different parameters (i.e., data usage, stall events, and video quality) of video streaming. WISH has been implemented into ExoPlayer, a popular player used in many mobile applications. The experimental results show that WISH improves the QoE by up to 17.6% while saving 36.4% of data usage compared to state-of-the-art ABR algorithms and provides dynamic adaptation to end users' requirements.
WISH: User-centric Bitrate Adaptation for HTTP
Adaptive Streaming on Mobile Devices
Minh Nguyen, Ekrem C¸ etinkaya, Hermann Hellwagner, Christian Timmerer
Christian Doppler Laboratory ATHENA, Institute of Information Technology (ITEC)
at Klagenfurt, Klagenfurt, Austria
Abstract—Recently, mobile devices have become paramount
in online video streaming. Adaptive bitrate (ABR) algorithms of
players responsible for selecting the quality of the videos face
critical challenges in providing a high Quality of Experience
(QoE) for end users. One open issue is how to ensure the optimal
experience for heterogeneous devices in the context of extreme
variation of mobile broadband networks. Additionally, end users
may have different priorities on video quality and data usage
(i.e., the amount of data downloaded to the devices through the
mobile networks). A generic mechanism for players that enables
specification of various policies to meet end users’ needs is still
missing. In this paper, we propose a weighted sum model, namely
WISH, that yields high QoE of the video and allows end users to
express their preferences among different parameters (i.e., data
usage, stall events, and video quality) of video streaming. WISH
has been implemented into ExoPlayer, a popular player used in
many mobile applications. The experimental results show that
WISH improves the QoE by up to 17.6% while saving 36.4%
of data usage compared to state-of-the-art ABR algorithms and
provides dynamic adaptation to end users’ requirements.
Index Terms—ABR Algorithms, HTTP Adaptive Streaming,
ITU-T P.1203, WISH
The COVID-19 pandemic has resulted in a remarkable
increase in video consumption due to the lockdown time.
Video content watched globally has increased by 60% [19].
In addition, Cisco [6] estimates that video data will occupy
82% of the Internet traffic by 2022. Mobile devices, including
smartphones and tablets, will also become predominant in
video streaming with more than 70% of watch time [20].
HTTP-based Adaptive Streaming (HAS) is a crucial tech-
nology for delivering videos over the Internet that brings
fewer stall events and higher video quality. In HAS, a video
at the server is encoded in multiple representations. Each
representation is further split into temporal segments. The
client executes an adaptive bitrate (ABR) algorithm to get
the most suitable representation of a segment before sending
an HTTP request to the server. Despite its popularity, video
streaming over HAS on mobile devices faces some challenges
such as severe throughput fluctuations in mobile broadband
networks [14] and the heterogeneity of mobile devices. The
former challenge makes it difficult for ABR algorithms to
select suitable bitrates to avoid stall events while keeping the
video in high quality. The latter means an ABR algorithm
might not be a one-size-fits-all solution to provide the optimal
Quality of Experience (QoE) for all mobile devices.
In this paper, we address the aforementioned problems by an
ABR algorithm based on a WeIghted Sum model for HAS,
namely WISH. WISH takes into account three cost factors
of each video representation: (a) throughput cost,(b) buffer
cost, and (c) quality cost. The throughput cost indicates the
amount of downloaded data which refers to the data usage of
mobile devices. The buffer cost and quality cost represent the
stalling risk and the deterioration in quality of a representation,
respectively. A low-quality representation with a small bitrate
provides a low throughput cost due to less data delivered in
broadband networks and a low buffer cost because of less
time to download, with low risk of stalling events. However, it
suffers from high quality cost due to a low quality. An overall
cost, which is a weighted sum of these penalties, represents
each video representation. Our proposed method provides
the optimal segment bitrate by choosing the representation
with the lowest overall cost for a certain time. A solution
determining the weights of the cost factors based on end users’
preferences and mobile devices will be introduced in this work.
WISH’s source code is available on Github1.
In summary, the contributions of this paper are three-fold:
1) WISH. We propose a novel ABR algorithm with the
objective of trading off the video quality, rebuffering,
and mobile devices’ data usage. Our approach considers
three categories of costs of each video representation
and selects the lowest-cost representation for the next
2) Weights determination. Each cost has a specific impact
on the overall cost function illustrated by a weight. End
users express their preferences by setting corresponding
weights. We propose a mathematical formula to map
the end user’s needs to the weights’ values, rather than
determining them by conjecture and empiricism.
3) Evaluation. Extensive experiments with various test se-
quences have been conducted to compare WISH with
state-of-the-art ABR algorithms. Moreover, WISH’s abil-
ity to reflect end user preferences in video streaming is
investigated in our experiments.
The remainder of this paper is structured as follows. Sec-
tion II provides an overview of related work. The details of
WISH are presented in Section III. The experimental results
are discussed in Section IV and the conclusions are provided
in Section V.
1The URL of the source code will be provided upon acceptance.
Many ABR algorithms have been proposed in the literature,
which can be classified into (i) throughput-based,(ii) buffer-
based, and (iii) hybrid-based [4]. A simple throughput-based
ABR algorithm that selects the highest bitrate but smaller than
the estimated throughput is used as a default in ExoPlayer2
a media player commonly used in thousands of applications,
including YouTube and WhatsApp [13]. As a buffer-based
algorithm, BBA-0 [7] relies on an increasing function of
instant buffer status to determine segments’ qualities. If the
current buffer is less than a low threshold, the lowest quality
level is chosen. If it is more than a high threshold, BBA-
0 selects the highest quality level. Otherwise, the value of
that function demonstrates the next segment’s representation.
Wang et al. [23] propose a hybrid-based ABR algorithm,
namely SQUAD, that takes into account the available through-
put and buffer occupancy. SQUAD starts the streaming session
with multiple low-quality segments. Then, this approach uses
a so-called spectrum, which is the variation of the segment
bitrates, to minimize the number of switches and maximize the
average video bitrate. The selected representation should be
sustainable (i.e., the estimated download time does not exceed
the segment duration) and provides the lowest spectrum (i.e.,
the least bitrate variation).
Many approaches have been introduced for adaptive video
streaming to mobile devices. Ara´
ujo et al. [2] propose the
Energy-Saving Based Adaptation Algorithm (ESBA) that has
the goal to utilize the energy of the devices efficiently. To
determine the segment quality, ESBA not only considers
throughput estimation and buffer information but also takes
into account battery voltage and the energy power usage.
Yan et al. [25] design a Rate and Brightness (RnB) adaptation
framework. The relationship among bitrate, video quality,
and devices’ screen brightness is investigated. A suitable
bitrate and corresponding brightness are then selected accord-
ing to the throughput and representation’s quality to mini-
mize the power consumption of video streaming. This strat-
egy requires additional representations, namely luminance-
compensated versions, to those that are already encoded at
the server, to enable energy adaptation. It might lead to more
storage consumption at the server and decrease the scalability
of the ABR algorithm.
Weighted sum models have been utilized recently in HAS.
Nguyen et al. [16] propose a cost function as a weighted
sum of buffer cost and request cost to select the number of
segments to be downloaded by a single request in adaptive
video streaming over HTTP/2 [3], [15]. A high number of
segments may harm the buffer when the throughput drops
as the client has to download all of these segments before
switching to a lower quality level. In return, there are fewer
requests sent to the server, which reduces network overhead;
in other words, the request cost goes down. Similar to this
work, Le et al. [10] add a smoothness-related cost to penalize
a quality level if it differs from the quality of the current
TABLE I: Notations used in this paper.
Notation Definition
NThe number of representations
RThe set of available bitrates R={R1, R2, ..., RN}
τSegment duration
q(i)Quality of representation i
QnQuality of segment n
TnAverage throughput measured at segment n
nSmoothed throughput at segment n
TeEstimated throughput for the next segment
BBuffer size
BlThreshold of low buffer occupancy
BnBuffer occupancy at segment n
segment. Compared to these approaches, our proposed method
considers the throughput cost and the quality cost. The former
cost is the amount of data downloaded in a second compared
to the available throughput, whereas the latter includes the
difference between a quality level and the highest representa-
tion, and between that quality level and the average quality of
recent segments. Moreover, the weights of the cost elements
in the related papers are chosen empirically. In contrast, we
introduce a mathematical method to determine dynamically
those parameters based on the video profile (i.e., bitrate ladders
and segment duration), client characteristics (i.e., buffer size),
and end users’ preferences.
A. Throughput Estimation
The simplest method to estimate the future throughput Te
is using the average throughput Tnof the current segment n.
Due to strong throughput variations in mobile networks, this
strategy may result in serious fluctuation of Tethat causes
frequent switches in the selected qualities. To tackle this issue,
we implement the “smooth” method introduced in [1]:
n=((1 ω)×Ts
n1+ω×Tn,if n > 1,
Tn,if n= 1,(1)
where Ts
nis the smooth throughput for downloading seg-
ment nand ωis a weight in the range [0,1]. In our paper,
ωis set to 1/8for smoothing computation, which is similar
to [9], [18].
A disadvantage of the “smooth” method is that it might
react late with the throughput decrease [9]. Therefore, we set
the estimated throughput as the last measured throughput if
the network is unfavorable. Otherwise, the smooth throughput
is used. The estimated throughput is determined as follows:
Te= min{Ts
n, Tn}.(2)
B. WISH ABR Algorithm
In this section, we describe our proposed WISH algorithm
that selects the quality of the next segment according to the
lowest-cost outcome. The notations used in our algorithm are
shown in Table I.
1) Start-up phase:If the current buffer level Bnis less than
a threshold Bl, then the buffer is in a dangerous zone with
high stall possibility. WISH selects the lowest representation
to start the playback as fast as possible at the beginning of the
streaming session and to decrease the risk of stalls.
2) Steady phase:If the current buffer exceeds Bl, the
streaming session switches to a steady phase. In this phase,
WISH calculates the cost of representation i,C(i), which is a
weighted sum of throughput cost Ct(i),buffer cost Cb(i), and
quality cost Cq(i)as presented in Eq. (3); the weights α, β, γ
are positive numbers:
C(i) = α×Ct(i) + β×Cb(i) + γ×Cq(i).(3)
The throughput cost of a representation is calculated as a
linearly increasing function of its bitrate as follows:
Ct(i) = Ri
The buffer cost is defined based on the following obser-
vations. While downloading representation i, the buffer is
drained by the download time, which is Ri×τ
Te. The higher the
download time, the more the buffer is decreased. Also, with
the same download time, a buffer at a low level has a higher
risk of under-running, which would result in a stall event.
Therefore, the buffer cost of representation iis computed as:
Cb(i) = Ri×τ
Finally, the quality cost comprises two sub-penalties: (i) a
penalty when a representation is lower than the highest-bitrate
representation, and (ii) a penalty if it is different from the
average quality of the recent segments. To make the quality
cost positive, we use an exponential function:
Cq(i) = e[q(N)q(i)]+[Qkq(i)]
e2×q(N)2×q(1) ,(6)
where q(i)is the quality of representation i, and Qkis the
average quality of the last ksegments (default k= 10). In
this paper, we use the bitrate Rito calculate the quality of the
i-th representation as:
q(i) = Ri
Our proposed ABR algorithm is presented in Algorithm 1.
As the lowest bitrate is selected in the start-up phase when
the buffer occupancy is too small, it is reasonable to omit
this representation when the buffer is not in danger. Thus, the
minimum considered representation is the second-lowest one
in the steady phase (line 7 in Algorithm 1). Also, when a high
bitrate level is selected, and afterward, the throughput suddenly
drops, the buffer occupancy will be decreased dramatically,
which might result in a low bitrate for the next decisions and
QoE impairment. To avoid this issue, WISH only considers the
representations whose bitrates are less than the last throughput
with the margin µ(µ= 0.1in this paper) (lines 8 – 9 in
Algorithm 1).
C. Weights determination
It is nontrivial to find suitable values for the weight set
(α, β, γ ) that meet the end users’ needs and provide a high
QoE. In this work, we introduce a strategy to dynamically set
the weights according to videos’ characteristics.
Algorithm 1: WISH ABR algorithm.
1if Bn< Blthen
i=0 Qni;
5m= 2;
6M= max{i|Ri< Tn×(1 + µ), m iN};
7for i=m, m + 1, ..., M do
8Ct(i) = Ri
9Cb(i) = Ri×τ
10 Cq(i) = e[q(N)q(i)]+[Qkq(i)]
e2×q(N)2×q(1) ;
11 C(i) = α×Ct(i) + β×Cb(i) + γ×Cq(i);
12 jmin = arg min
13 Rc=Rjmin ;
14 return Rc;
The cost C(i)can be considered as a function f(Ri)of the
bitrate Rias follows:
f(Ri) = α×Ri
e2×q(N)2×q(1) .
The derivative of f(Ri)is presented in Eq. (9).
where A=e2×q(N)2×q(1) is a constant. It can be seen that
the value of Rithat makes f(Ri)lowest is Xif f0(X)=0.
The weights α, β, γ are determined by making the maxi-
mum bitrate RNown the lowest cost (i.e.,f0(RN)=0) under
the following conditions. Firstly, the estimated throughput Te
should be high enough, compared to the maximum bitrate RN,
to avoid buffer drainage. Secondly, the average quality of the
last segments Qkis high to indicate that the recent network
condition is favorable. Finally, the current buffer Bnneeds
to be high to prevent stall events in the case of a sudden
throughput drop. These constraints are described as follows:
f0(RN) = 0, if
Qk= Q
where δ(δ > 0) indicates the capability of the network to
deliver the maximum bitrate and ξ(0,1] is the proportion
of filled buffer. Qis a threshold representing the recent average
quality is in high level. In this paper, we set ξ= 0.8, which
is similar to [18], δ= 1, and Q = q(RN1)as default.
Now, we need to find (α, β, γ ) to obtain (). Without loss
of generality, we can set the sum of these parameters to 1 (i.e.,
α+β+γ= 1). For relaxation, we set α, β so that throughput
and buffer costs have the same contribution in the overall cost
of the highest representation (i.e.,α×Ct(N) = β×Cb(N)).
Thus, the relationship of α, and βcan be demonstrated as
Finally, the weights α, β, γ can be determined as follows:
α= (1 + ξ×BBl
γ= 1 αβ
A. Experimental Setup and Metrics
Our testbed consists of a server and a client connected via
a WIFI interface. The server hosts an Apache web server
running on a Thinkpad P1 Gen2 (i7/16GB) with Ubuntu 18.04.
WISH is implemented in ExoPlayer running on a Xiaomi Mi
11 (256 GB, Android 11). The buffer size of this player is set
to 20s (B= 20) and the threshold Blis equal to 4s.
The network conditions are controlled by the Linux traffic
control tool, tc, on the server. In our experiments, a 4G
network trace [21] collected on bus rides is used to emulate
the mobile network conditions. The average bandwidth in this
trace is 3787 Kbps with a standard deviation of 3193 Kbps,
and the maximum bandwidth is 17361 Kbps. The round trip
time is set to 20ms that is reasonable in 4G networks3.
We use four videos as the test sequences stored at the server,
each of which is 5 minutes long: (i) Tears of Steel (the first 5
mintues) – ToS1, (ii) Gameplay4[24], (iii) Rally 5,(iv) Tears
of Steel (the last 5 minutes) – ToS2. We want to choose
videos with different characteristics as our test sequences.
The Rally sequence consists of natural captured content, the
Gameplay sequence consists of computer-generated content,
and the ToS1 and ToS2 sequences contain both natural and
computer-generated content. These characteristics make them
a suitable set of test sequences. Moreover, these videos have
different spatial information (SI) and temporal information
(TI) as shown in Fig. 1. The test sequences are encoded into
seven quality levels R={107, 240, 346, 715, 1347, 2426,
4121}Kbps at {144, 240, 360, 480, 720, 1080, 1440}p res-
olutions, respectively, using the state-of-the-art H.265/HEVC
codec. HEVC is chosen as the codec since market-adaption
of the H.266/VVC is still too limited, and using H.264/AVC
would not have been suitable as it is more than a decade
old. The bitrate ladder is based on the ToS video stored in
Youtube6. Each quality level is then divided into segments of
4s (τ= 4) as recommended in [5]. WISH is compared with
three state-of-the-art approaches described in Section II, i.e.,
BBA-0, SQUAD, and the default ABR algorithm of ExoPlayer,
each of which belongs to a class of ABR algorithms [4].
The performance of those ABR algorithms is evaluated with
common QoE-related metrics as follows:
Fig. 1: Spatial and temporal information of the test sequences.
Average bitrate: The average bitrate of all the segments
downloaded by the client.
Number of switches: The number of segments whose
bitrate is lower than that of their previous one.
Video instability: The average change in the level of
representation of contiguous segments.
Number of stalls and stall duration: The number of
rebuffering and the total video freeze time, respectively.
QoE scores: ITU-T Rec.P.1203 mode 0 [8] is used
to estimate the perception QoE of the end users. The
implementation of this model [22] with its extension for
up to 4K HEVC videos is available on Github7.
For accuracy, each ABR scheme is executed five times
and the averages and standard deviations are presented in the
B. Experimental Results
1) WISH performance compared to state-of-the-art ABR
algorithms: Fig. 2–Fig. 5 show the performance of WISH
with the default setup and existing ABR schemes for different
videos. It can be seen that WISH achieves the highest QoE
scores for all test sequences, as illustrated in Fig. 2. Its QoE
scores are in the range of 3.46 (GamePlay) to 3.71 (ToS2),
whereas this figure for other related work is no more than
3.40 in most cases except ExoPlayer in the ToS2 video. Thus,
WISH’s QoE scores are higher than others by up to 17.6%.
An interesting finding is that the built-in ABR algorithm of
ExoPlayer yields better QoE scores than BBA-0 and SQUAD.
It can be attributed to the number of stalls and stall duration
of those ABR algorithms in Fig. 3. WISH has the fewest
number of stalls with at most one stall. In particular, there is
not any stall in ToS1 and ToS2 videos. Regarding GamePlay
and Rally videos, WISH experiences on average 0.4 stall
events that last for 1.1s and 1.2s, respectively. On the other
hand, BBA-0 and SQUAD suffer severely from stalls with
on average more than two stall events, and the stall duration
varies from 15s to 30s, which may make the end users
quit the video watching [11], [12]. This is because BBA-0
only takes the current buffer occupancy into account without
considering the network condition, and SQUAD makes an
effort to provide stable-quality videos. These strategies react
slowly to the severe throughput fluctuation, which results in
Fig. 2: ITU-T QoE scores.
Fig. 3: Number of stalls and stall duration.
Fig. 4: Average bitrate of each segment.
Fig. 5: Video instability.
long stall duration when the throughput drops significantly. In
contrast, ExoPlayer adapts quickly to the network oscillation;
thus, it reduces the number of stalls to less than two, and the
stall duration is from 3.8s (ToS2 video) to 17.0s (GamePlay),
but still more than when using WISH. With the objective of
balancing bitrate, stalls, and segment quality, WISH does not
try to download high-quality segments, which avoids stalls
when the network is unfavorable.
The average bitrate of ABR algorithms is reported in Fig. 4.
In general, BBA-0 downloads segments with the highest
average bitrate, whereas this figure for WISH is the lowest.
Each segment in BBA-0 has an average bitrate of 2800 Kbps,
which is higher than that in WISH by 36.4%. ExoPlayer
and SQUAD provide 2198 Kbps and 2670 Kbps segments,
respectively, compared to 2053 Kbps segments of WISH. It
should be noted that the higher the average bitrate, the more
data usage. Therefore, WISH saves a large amount of data
usage from 7.1% to 36.4%. These analyses reveals that WISH
is able to trade off video quality, buffer (i.e., stalls and stall
duration), and mobile devices’ data usage.
However, to achieve such performance, WISH sacrifices the
video stability (Fig. 5). The video instability of our method
is around 0.6, compared to 0.51, 0.54, and 0.42 of BBA-0,
ExoPlayer, and SQUAD, respectively. On average, there are
less than six quality switches in BBA-0 and SQUAD as these
methods adapt gradually with the throughput drop. On the
other hand, WISH and ExoPlayer experience respectively 14.8
and 15 quality switches in each streaming session.
2) WISH performance with different end user preferences:
Table II shows the WISH’s results with different end user
preferences by changing the safe threshold ξof the buffer.
The requirement of the high video quality is increased from
preference #1 (γ= 0.68, ξ = 1.0) to preference #4 (γ=
0.84, ξ = 0.4). The QoE scores are not reported here as the
ITU-T P.1203 model provides the scores for general viewers
and it might not reflect correctly the experience of end users
with specific preferences.
In Table II, the average bitrate acquired by WISH increases
with γ, from 1841 Kbps at γ= 0.68 to 2270 Kbps at γ=
0.84. Additionally, there is a growth in the video instability
with 0.54 in #1 and 0.61 in #4, and the average number of
switches (13.4 switches to 15.0 switches). This is attributed
to the effort of selecting segments in high bitrates. When γis
set to a large value, a small increase in Cq(i)due to a low
bitrate results in a severe penalty in the overall cost C(i)and
WISH tries to download high bitrate levels though the network
conditions are unfavorable. Consequently, the buffer might be
decreased thoroughly, and lower bitrates have to be selected
TABLE II: WISH performance with different end user preferences for ToS2.
Preference #1 (ξ= 1.0) #2 (ξ= 0.8) #3 (ξ= 0.6) #4 (ξ= 0.4)
Average bitrate (Kbps) 1841 2002 2107 2270
Average video instability 0.54 0.57 0.58 0.62
Average # of switches 13.4 14.0 14.6 15.0
Average # of stall & stall duration (s) 0 & 0 0 & 0 0 & 0 0.6 & 5.3
(α, β, γ )(0.06, 0.26, 0.68) (0.07, 0.21, 0.72) (0.07, 0.15, 0.78) (0.08, 0.08, 0.84)
for upcoming segments, or the playback stalls if the buffer
is empty (e.g., in #4 with an average of 0.6 stalls that lasts
for 5.3s in each session). Because the estimated throughput is
conservative in increasing network conditions, the bitrates of
later segments are increased conservatively, and the average
video instability is higher than for the end user preferences in
which the video quality owns a lower priority.
In this paper, we introduced a weighted sum model, named
WISH, to provide high QoE for mobile devices and to meet
end users’ requirements. WISH considers three types of cost,
i.e.,throughput cost,buffer cost, and quality cost, of each video
representation and combines them in a weighted sum as the
overall cost. The representation with the lowest overall cost
is selected. This strategy allows end users to express their
preferences by varying the weight of each cost. We also pro-
pose a mathematical solution to choose those weights based on
video characteristics (i.e., bitrate ladder, segment duration), the
client (i.e., buffer), and end users’ priorities. WISH has been
deployed into ExoPlayer, a common media player utilized
in commercial mobile applications. The experimental results
show that the proposed method needs the lowest data usage
while keeping the highest QoE scores. In the future, we will
integrate the retransmission technique H2BR [17] to improve
the video stability of WISH.
The financial support of the Austrian Federal Ministry for Digital
and Economic Affairs, the National Foundation for Research, Tech-
nology and Development, and the Christian Doppler Research As-
sociation, is gratefully acknowledged. Christian Doppler Laboratory
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... where is the estimated throughput. can be calculated by a "smooth" throughput [8] and the last measured throughput as in [118]. The next segment contributes a period of segment duration to the buffer but also drains the buffer by where is the current buffer occupancy and ∈{ | ̸ = } is the total bitrate of the next and upgraded segments. ...
... The higher the current buffer level, the more bitrate can be downloaded. On the other hand, hybrid algorithms [118,181] consider both buffer occupancy and network conditions. WISH [118] considers three kinds of cost for each representation (i.e., throughput cost, buffer cost, and quality cost) and selects the quality level with the lowest total cost according to a weighted sum model. ...
... On the other hand, hybrid algorithms [118,181] consider both buffer occupancy and network conditions. WISH [118] considers three kinds of cost for each representation (i.e., throughput cost, buffer cost, and quality cost) and selects the quality level with the lowest total cost according to a weighted sum model. Wang et al. [181] proposed SQUAD to minimize the quality variations as well as to maximize the average bitrate based on an online optimization algorithm. ...
... where T e is the estimated throughput. T e can be calculated by a "smooth" throughput [44] and the last measured throughput as in [45]. The next segment s k contributes a period of segment duration τ to the buffer but also drains the buffer by its download time t down i . ...
Full-text available
HTTP Adaptive Streaming (HAS) solutions use various adaptive bitrate (ABR) algorithms to select suitable video qualities with the objective of coping with the variations of network connections. HTTP has been evolving with various versions and provides more and more features. Most of the existing ABR algorithms do not significantly benefit from the HTTP development when they are merely supported by the most recent HTTP version. An open research question is “ How can new features of the recent HTTP versions be used to enhance the performance of HAS ?” To address this question, in this paper, we introduce Days of Future Past+ (DoFP+ for short), a heuristic algorithm that takes advantage of the features of the latest HTTP version, HTTP/3, to provide high Quality of Experience (QoE) to the viewers. DoFP+ leverages HTTP/3 features, including (i) stream multiplexing , (ii) stream priority , and (iii) request cancellation to upgrade low-quality segments in the player buffer while downloading the next segment. The qualities of those segments are selected based on an objective function and throughput constraints. The objective function takes into account two factors, namely the (i) average bitrate and the (ii) video instability of the considered set of segments. We also examine different strategies of download order for those segments to optimize the QoE in limited resources scenarios. The experimental results show an improvement in QoE by up to 33% while the number of stalls and stall duration for DoFP+ are reduced by 86% and 92%, respectively, compared to state-of-the-art ABR schemes. In addition, DoFP+ saves on average up to 16% downloaded data across all test videos. Also, we find that downloading segments sequentially brings more benefits for retransmissions than concurrent downloads; and lower-quality segments should be upgraded before other segments to gain more QoE improvement. Our source code has been published for reproducibility at DoFP-Plus.
Full-text available
HTTP Adaptive Streaming (HAS) plays a key role in over-the-top video streaming with the ability to reduce the video stall duration by adapting the quality of transmitted video segments to the network conditions. However, HAS still suffers from two problems. First, it incurs variations in video quality because of throughput fluctuation. Adaptive bitrate (ABR) algorithms at the HAS client usually select a low-quality segment when the throughput drops to avoid stall events, which impairs the Quality of Experience (QoE) of the end-users. Second, many ABR algorithms choose the lowest-quality segments at the beginning of a video streaming session to ramp up the playout buffer early on. Although this strategy decreases the startup time, clients can be annoyed as they have to watch a low-quality video initially. To address these issues, we introduced the H2BR technique (HTTP/2-Based Retransmission) [35] that utilizes certain features of HTTP/2 (including server push, multiplexing, stream priority, and stream termination) for late transmissions of higher-quality versions of video segments already in the client buffer, in order to improve video quality. Although H2BR was shown to enhance the QoE, limited streaming scenarios were considered resulting in a lack of general conclusions on H2BR's performance. Thus, this article provides a profound evaluation to answer three open questions: (i) how H2BR's performance is impacted by parameters at the server side (i.e., various encoding specifications), at the network side (i.e., packet loss rate), and at the client side (i.e., buffer size) on the performance of H2BR; (ii) how H2BR outperforms other state-of-the-art approaches in different configurations of the parameters above; (iii) how to effectively utilize H2BR on top of ABR algorithms in various streaming scenarios. The experimental results show that H2BR's performance increases with the buffer size and decreases with increasing packet loss rates and/or video segment duration. The number of quality levels can negatively or positively impact on H2BR's performance, depending on the ABR algorithm deployed. In general, H2BR is able to enhance the video quality by up to 17% and 14% in scalable video streaming and in non-scalable video streaming, respectively. Compared with an existing retransmission technique (i.e., SQUAD [49]), H2BR shows better results with more than 10% in QoE and 9% in the average video quality.
Conference Paper
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HTTP-based Adaptive Streaming (HAS) plays a key role in over-the-top video streaming. It contributes towards reducing the rebuffering duration of video playout by adapting the video quality to the current network conditions. However, it incurs variations of video quality in a streaming session because of the throughput fluctuation, which impacts the user’s Quality of Experience (QoE). Besides, many adaptive bitrate (ABR) algorithms choose the lowest-quality segments at the beginning of the streaming session to ramp up the playout buffer as soon as possible. Although this strategy decreases the startup time, the users can be annoyed as they have to watch a low-quality video initially. In this paper, we propose an efficient retransmission technique, namely H2BR, to replace low-quality segments being stored in the playout buffer with higher-quality versions by using features of HTTP/2 including (i) stream priority, (ii) server push, and (iii) stream termination. The experimental results show that H2BR helps users avoid watching low video quality during video playback and improves the user’s QoE. H2BR can decrease by up to more than 70% the time when the users suffer the lowest-quality video as well as benefits the QoE by up to 13%.
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The number of mobile devices that use video streaming applications has been steadily rising year after year. Platforms responsible for providing multimedia service face great challenges in delivering high-quality content for mobile users. One main problem in sharing video flows is the high energy consumption in mobile devices, which reduces their lifetime. A video adaptation approach with Quality of Experience (QoE) support is a key issue to increase the user experience while watching videos as well as reduce the energy consumption in mobile devices. In this paper, we propose a hybrid energy-aware video bitrate adaptation algorithm to deliver videos with high QoE and energy-efficiency for mobile users. Simulation results show the efficiency of the proposed algorithm compared to existing adaptation video bitrate algorithms, reducing the number and duration of stalls, as well as saving energy.
Full-text available
In this survey, we present state-of-the-art bitrate adaptation algorithms for HTTP adaptive streaming (HAS). As a key distinction from other streaming approaches, the bitrate adaptation algorithms in HAS are chiefly executed at each client, i.e., in a distributed manner. The objective of these algorithms is to ensure a high Quality of Experience (QoE) for viewers in the presence of bandwidth fluctuations due to factors like signal strength, network congestion, network reconvergence events, etc. While such fluctuations are common in public Internet, they can also occur in home networksor even managed networks where there is often admission control and QoS tools. Bitrate adaptation algorithms may take factors like bandwidth estimations, playback buffer fullness, device features, viewer preferences, and content features into account, albeit with different weights. Since the viewer’s QoE needs to be determined in real-time during playback, objective metrics are generally used including number of buffer stalls, duration of startup delay, frequency and amount of quality oscillations, and video instability. By design, the standards for HAS do not mandate any particular adaptation algorithm, leaving it to system builders to innovate and implement their own method. This survey provides an overview of the different methods proposed over the last several years. OAPA
Conference Paper
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In this paper, we present a 4G trace dataset composed of client-side cellular key performance indicators (KPIs) collected from two major Irish mobile operators, across different mobility patterns (static, pedestrian, car, bus and train). The 4G trace dataset contains 135 traces, with an average duration of fifteen minutes per trace, with viewable throughput ranging from 0 to 173 Mbit/s at a granularity of one sample per second. Our traces are generated from a well-known non-rooted Android network monitoring application, G-NetTrack Pro. This tool enables capturing various channel related KPIs, context-related metrics, downlink and uplink throughput, and also cell-related information. To the best of our knowledge, this is the first publicly available dataset that contains throughput, channel and context information for 4G networks. To supplement our real-time 4G production network dataset, we also provide a synthetic dataset generated from a large-scale 4G ns-3 simulation that includes one hundred users randomly scattered across a seven-cell cluster. The purpose of this dataset is to provide additional information (such as competing metrics for users connected to the same cell), thus providing otherwise unavailable information about the eNodeB environment and scheduling principle, to end user. In addition to this dataset, we also provide the code and context information to allow other researchers to generate their own synthetic datasets.
Conference Paper
Full-text available
This paper describes an open dataset and software for ITU-T Rec. P.1203. As the first standardized Quality of Experience model for audiovisual HTTP Adaptive Streaming (HAS), it has been extensively trained and validated on over a thousand audiovisual sequences containing HAS-typical effects (such as stalling, coding artifacts, quality switches). Our dataset comprises four of the 30 official subjective databases at a bitstream feature level. The paper also includes subjective results and the model performance. Our software for the standard was made available to the public, too, and it is used for all the analyses presented. Among other previously unpublished details , we show the significant performance improvements of using bitstream-based models over metadata-based ones for video quality analysis, and the robustness of combining classical models with machine-learning-based approaches for estimating user QoE.
Full-text available
Video streaming over HTTP/2 is a new trend in multimedia delivery. Compared to the pull-based HTTP/1.1 protocol, the new HTTP/2 protocol's Server Push feature is very effective in reducing the overheads (e.g., in terms of energy, processing, bandwidth) for clients, servers, and network nodes. This paper presents an HTTP/2 push-based adaptation method for on-demand video streaming that reduces the number of requests and provides high video quality. In our method, for each client request, the server sends video segments continuously until it receives another client request with a new quality. Since a request is sent only if the client wants to update the video bitrate, our method can significantly reduce the request related overhead. For this context, a buffer based algorithm is proposed to provide high and smooth video quality while avoiding buffer underflows. Experiments show that the proposed method can provide a lower number of requests, higher average quality and better quality smoothness than existing methods.
HTTP Adaptive Streaming (HAS) has become a key technology for delivering videos over the mobile Internet. To cope with throughput variations during a streaming session, an HTTP streaming client should answer two key questions: (1) “should the current bitrate be maintained?” and (2) “if not, which new bitrate should be requested?” This paper presents a buffer-based adaptation method that systematically answers these two questions. By considering the trend of the buffer level in the near future, our method reasonably decides a buffer range for maintaining the bitrate. Moreover, when the bitrate should be reduced, the proposed method smartly selects the bitrate to yield smooth reductions while avoiding buffer underflows. Through evaluation with time-varying bandwidths of mobile networks, we show that the proposed method can provide high average bitrate, gradual transitions, and buffer stability.