Computer Science

Permanent URI for this collectionhttps://hdl.handle.net/10679/43

Browse

Now showing 1 - 20 of 63

Metadata only
Adaptive streaming of content-aware-encoded videos in dash.js
(IEEE, 2022-05) Beğen, Ali Cengiz; Akçay, Mehmet Necmettin; Bentaleb, A.; Giladi, A.; Computer Science; BEĞEN, Ali Cengiz; Akçay, Mehmet Necmettin
In Hypertext Transfer Protocol (HTTP) adaptive streaming, the client makes rate adaptation decisions based on the measured network bandwidth and buffer fullness. This simplifies the adaptation logic; however, it often produces noticeable quality fluctuations during the streaming session. With content-aware encoding (CAE), one can improve the visual quality without increasing the total number of bits spent by carefully choosing where the bits are spent based on human perception. However, an adaptation logic that is unaware of the resulting variable-size segments may cause more stalls, defeating the purpose of improving viewer experience through CAE. This article explains the design steps of a size-aware rate adaptation (SARA) logic for one of the most popular Dynamic Adaptive Streaming over HTTP (DASH) clients, namely dash.js, and shows the improvements in rebuffering behavior and fetching top-resolution segments as a result of applying this logic.
Metadata only
Adjusting content work flow infrastructures for HDR
(IEEE, 2018-11-28) Syed, Y.; Beğen, Ali Cengiz; Computer Science; BEĞEN, Ali Cengiz
This paper discusses what areas of a content workflow infrastructure are affected by integrating new high dynamic range (HDR) video formats into the system while also still continuing to process the standard dynamic range (SDR) format of the content. First, we present the history of SDR and what benefits HDR can bring. We then look at potential efficiencies in the capture-production-distribution domains where the HDR/SDR paths do not need to be separated and other places where they should be separated to avoid a potential loss in quality. Lastly, we discuss some of the HDR variants and how the infrastructure could handle dynamic metadata as it passes through the relevant workflow domains.
Metadata only
Are the streamingformat wars over?
(IEEE, 2018-11-28) Beğen, Ali Cengiz; Syed, Y.; Computer Science; BEĞEN, Ali Cengiz
An average US viewer watches some form of video content five hours a day. The majority ofthe viewed content is still broadcast (over the air, cable, IPTV or satellite), however, the share of the streaming content has been on the rise. In the past year, we witnessed some much needed convergence in the standards and the industry, and as a result of this, the forecast forstreaming services looks more promising than ever.
Metadata only
Automated adaptive playback for encoder-adjudicated live sports
(IEEE, 2022) Akgul, T.; Uğur, Deniz; Beğen, Ali Cengiz; Computer Science; BEĞEN, Ali Cengiz; Uğur, Deniz
In low-latency live streaming, it is not easy to simultaneously avoid stalls and maintain low latency. The trade-off needs to be decided in real time. One of the best tools for controlling the buffer level (hence, the stalls) and live latency is adaptive playback speed control, which slows down the playback when the buffer level is critically low to reduce the risk of stalling and speeds up the playback when the buffer is sufficiently full to reduce the live latency. Adaptive playback generally works well. However, it may introduce artifacts depending on the content. Viewers may be more sensitive to playback speed changes at certain scenes. In this paper, we augment the state-of-the-art content-aware playback speed control (CAPSC) algorithm by developing a post-encoder add-on tool that analyzes the encoded live content and automatically tags each output chunk with a value indicating its suitability for playback speed changes. The source code for the CAPSC algorithm and the new post-encoder add-on (developed for the snooker games) is publicly available.
Metadata only
Automated objective and subjective evaluation of HTTP adaptive streaming systems
(IEEE, 2018-06-26) Timmerer, C.; Zabrovskiy, A.; Beğen, Ali Cengiz; Computer Science; BEĞEN, Ali Cengiz
Streaming audio and video content currently accounts for the majority of the internet traffic and is typically deployed over the top of the existing infrastructure. We are facing the challenge of a plethora of media players and adaptation algorithms showing different behavior but lack a common framework for both objective and subjective evaluation of such systems. This paper aims to close this gap by (i) proposing such a framework, (ii) describing its architecture, (iii) providing an example evaluation, (iv) and discussing open issues.
Metadata only
Bandwidth prediction in low-latency chunked streaming
(The ACM Digital Library, 2019-06) Bentaleb, A.; Timmerer, C.; Beğen, Ali Cengiz; Zimmermann, R.; Computer Science; BEĞEN, Ali Cengiz
HTTP adaptive streaming with chunked transfer encoding can be used to offer low-latency streaming without sacrificing the coding efficiency. While this allows a media segment to be generated and delivered at the same time, which is critical in reducing the latency, the conventional bitrate adaptation schemes make often grossly inaccurate bandwidth measurements due to the presence of idle periods between the chunks. These wrong measurements cause the streaming client to make bad adaptation decisions. To this end, we design ACTE, a new bitrate adaptation scheme that leverages the unique nature of chunk downloads. ACTE uses a sliding window to accurately measure the available bandwidth and an online linear adaptive filter to predict the bandwidth into the future. Results show that ACTE achieves 96% measurement accuracy, which translates to a 65% reduction in the number of stalls and a 49% increase in quality of experience on average compared to other schemes.
Open Access
Bandwidth prediction in low-latency media transport
(ACM, 2023-06-16) Bentaleb, A.; Akçay, Mehmet Necmettin; Lim, M.; Beğen, Ali Cengiz; Zimmermann, R.; Computer Science; BEĞEN, Ali Cengiz; Akçay, Mehmet Necmettin
Designing a robust bandwidth prediction algorithm for low-latency media transport that can quickly adapt to varying network conditions is challenging. In this paper, we present the working principles of a hybrid bandwidth predictor (termed BoB, Bang-on-Bandwidth) we developed recently for real-time communications and discuss its use with the new Media-over-QUIC (MOQ) protocol proposals.
Metadata only
Benchmarking the second edition of the omnidirectional media format standard
(IEEE, 2022) Kara, Burak; Akçay, Mehmet Necmettin; Beğen, Ali Cengiz; Ahsan, S.; Curcio, I. D. D.; Kammachi-Sreedhar, K.; Aksu, E.; Computer Science; BEĞEN, Ali Cengiz; Kara, Burak; Akçay, Mehmet Necmettin
Omnidirectional MediA Format (OMAF) is the first worldwide virtual reality (VR) standard to store and distribute immersive media, completed in 2019. Later, in 2021, the second edition of this standard (OMAF v2) was published. The second edition kept all the features defined in the first OMAF edition while introducing some new ones, such as overlays and multi-viewpoints. OMAF v2's Tile Index Segments that contain metadata to track fragment data per segment and quality levels create a bandwidth overhead. During the OMAF v2 standardization, multiple methods for the track fragment run representation were studied to deal with this overhead. This paper presents the implementation of one of these methods, the compressed box method using the DEFLATE algorithm (OMAF v2*). It also provides comprehensive test results of OMAF v1, OMAF v2 and OMAF v2∗ with various combinations of three tile grids (6x4, 8x6 and 12x8), three segment durations (300 ms, 900 ms and 3 s), two videos (RollerCoaster and Timelapse), two bitrate groups (each group with four different bitrates) and two HTTP versions (HTTP/1.1 and H2).
Open Access
The benefits of server hinting when DASHing or HLSing
(ACM, 2022-03-17) Lim, M.; Akçay, Mehmet Necmettin; Bentaleb, A.; Beğen, Ali Cengiz; Zimmermann, R.; Computer Science; BEĞEN, Ali Cengiz; Akçay, Mehmet Necmettin
Streaming clients almost always compete for the available bandwidth and server capacity. Not every client's playback buffer conditions will be the same, though, nor should be the priority with which the server processes the individual requests coming from these clients. In an earlier work, we demonstrated that if clients conveyed their buffer statuses to the server using a Common Media Client Data (CMCD) query argument, the server could allocate its output capacity among all the requests more wisely, which could significantly reduce the rebufferings experienced by the clients. In this paper, we address the same problem using the Common Media Server Data (CMSD) standard that is work-in-progress at the Consumer Technology Association (CTA). In this case, the incoming requests are scheduled based on their CMCD information. For example, the response to a request indicating a healthy buffer status is held/delayed until more urgent requests are handled. When the delayed response is eventually transmitted, the server attaches a new CMSD parameter to indicate how long the delay was. This parameter avoids misinterpretations and subsequent miscalculations by the client's rate-adaptation logic. We implemented the server and client understanding/processing CMCD and CMSD, respectively. Our experiments show that the proposed CMSD parameter effectively eliminates unnecessary downshifting while reducing both the rebuffering rate and duration.
Metadata only
Best papers of the 2016 ACM multimedia systems (MMSys) conference and workshop on network and operating system support for digital audio and video (NOSSDAV) 2016
(The ACM Digital Library, 2017-06) Timmerer, C.; Beğen, Ali Cengiz; Computer Science; BEĞEN, Ali Cengiz
N/A
Open Access
BoB: Bandwidth prediction for real-time communications using heuristic and reinforcement learning
(IEEE, 2023) Bentaleb, A.; Akçay, Mehmet Necmettin; Lim, M.; Beğen, Ali Cengiz; Zimmermann, R.; Computer Science; BEĞEN, Ali Cengiz; Akçay, Mehmet Necmettin
Bandwidth prediction is critical in any Real-time Communication (RTC) service or application. This component decides how much media data can be sent in real time. Subsequently, the video and audio encoder dynamically adapts the bitrate to achieve the best quality without congesting the network and causing packets to be lost or delayed. To date, several RTC services have deployed the heuristic-based Google Congestion Control (GCC), which performs well under certain circumstances and falls short in some others. In this paper, we leverage the advancements in reinforcement learning and propose BoB (Bang-on-Bandwidth) — a hybrid bandwidth predictor for RTC. At the beginning of the RTC session, BoB uses a heuristic-based approach. It then switches to a learning-based approach. BoB predicts the available bandwidth accurately and improves bandwidth utilization under diverse network conditions compared to the two winning solutions of the ACM MMSys'21 grand challenge on bandwidth estimation in RTC. An open-source implementation of BoB is publicly available for further testing and research.
Open Access
Catching the moment with LoL + in twitch-like low-latency live streaming platforms
(IEEE, 2022) Bentaleb, A.; Akçay, Mehmet Necmettin; Lim, M.; Beğen, Ali Cengiz; Zimmermann, R.; Computer Science; BEĞEN, Ali Cengiz; Akçay, Mehmet Necmettin
Our earlier Low-on-Latency (dubbed as LoL) solution offered an accurate bandwidth prediction and rate adaptation algorithm tailored for live streaming applications that targeted an end-to-end latency of up to two seconds. While LoL was a significant step forward in multi-bitrate low-latency live streaming, further experimentation and testing showed that there was room for improvement in three areas. First, LoL used hard-coded parameters computed from an offline training process in the rate adaptation algorithm and this was seen as a significant barrier in LoL's wide deployment. Second, LoL's objective was to maximize a collective QoE function. Yet, certain use cases have specific objectives besides the singular QoE and this had to be accommodated. Third, the adaptive playback speed control failed to produce satisfying results in some scenarios. Our goal in this paper is to address these areas and make LoL sufficiently robust to deploy. We refer to the enhanced solution as LoL+ which has been integrated to the official dash.js player in v3.2.0.
Open Access
Common media client data (CMCD): Initial findings
(Association for Computing Machinery, Inc, 2021-07-16) Bentaleb, A.; Lim, M.; Akçay, Mehmet Necmettin; Beğen, Ali Cengiz; Zimmermann, R.; Computer Science; BEĞEN, Ali Cengiz; Akçay, Mehmet Necmettin
In September 2020, the Consumer Technology Association (CTA) published the CTA-5004: Common Media Client Data (CMCD) specification. Using this specification, a media client can convey certain information to the content delivery network servers with object requests. This information is useful in log association/analysis, quality of service/experience monitoring and delivery enhancements. This paper is the first step toward investigating the feasibility of CMCD in addressing one of the most common problems in the streaming domain: efficient use of shared bandwidth by multiple clients. To that effect, we implemented CMCD functions on an HTTP server and built a proof-of-concept system with CMCD-Aware dash.js clients. We show that even a basic bandwidth allocation scheme enabled by CMCD reduces rebuffering rate and duration without noticeably sacrificing the video quality.
Open Access
Common media server data (CMSD) - update on implementations and validation of key use cases
(ACM, 2023-06-16) Pham, S.; Law, W.; Beğen, Ali Cengiz; Silhavy, D.; Berthelot, B.; Arbanowski, S.; Steglich, S.; Computer Science; BEĞEN, Ali Cengiz
The CTA-5006 (Common Media Server Data, CMSD) specification establishes a uniform method for media servers to exchange data with each media object response. The aim is to enhance distribution efficiency, performance, and ultimately, the user experience. We provide an overview of CMSD implementations and focus on integrating CMSD into the dash.js reference player. Three use cases are evaluated to demonstrate the advantages of CMSD, including leveraging edge server throughput estimates to improve initial bitrate selection and low-latency live streaming, prefetching manifests and segments to improve startup delay, and allowing an edge server to suggest a playback bitrate to improve the collective experience. The outcomes from the initial implementations confirm the benefits of using CMSD.
Metadata only
Consumer communications and the next generation broadcast networks
(IEEE, 2016) Beğen, Ali Cengiz; Kolberg, M.; Merabti, M.; Computer Science; BEĞEN, Ali Cengiz
Over 20 years ago the challenge for the communications community was the convergence between networking, telecommunication, and broadcasting. This challenge has been fairly well met, and we now note that around the world telco companies are being re-born as new hybrid telco-broadcast entities, and the reverse is true for many broadcasting corporations that provide Internet services in addition to their core business. Current and new infrastructure networks now face a number of major challenges that include increasing efficiency in the delivery of services from the installed or legacy systems, and an evolution path to address more topical concerns such as energy conservation and the increased heterogeneity in media, applications, and delivery systems. Central to all of these are the ever changing consumer communication habits and demands. These particular themes are addressed in this issue.
Metadata only
Content-aware playback speed control for low-latency live streaming of sports
(The ACM Digital Library, 2021) Aladağ, Ö. F.; Uğur, Deniz; Akçay, Mehmet Necmettin; Beğen, Ali Cengiz; Computer Science; BEĞEN, Ali Cengiz; Uğur, Deniz; Akçay, Mehmet Necmettin
There are two main factors that determine the viewer experience during the live streaming of sports content: latency and stalls. Latency should be low and stalls should not occur. Yet, these two factors work against each other and it is not trivial to strike the best trade-off between them. One of the best tools we have today to manage this trade-off is the adaptive playback speed control. This tool allows the streaming client to slow down the playback when there is a risk of stalling and increase the playback when there is no risk of stalling but the live latency is higher than desired. While adaptive playback generally works well, the artifacts due to the changes in the playback speed should preferably be unnoticeable to the viewers. However, this mostly depends on the portion of the audio/video content subject to the playback speed change. In this paper, we advance the state-of-the-art by developing a content-aware playback speed control (CAPSC) algorithm and demonstrate a number of examples showing its significance. We make the running code available and provide a demo page hoping that it will be a useful tool for the developers and content providers.
Metadata only
COSMOS on steroids: a Cheap detector for cheapfakes
(The ACM Digital Library, 2021) Akgül, T.; Civelek, Tuğçe Erkılıç; Uğur, Deniz; Beğen, Ali Cengiz; Computer Science; BEĞEN, Ali Cengiz; Civelek, Tuğçe Erkılıç; Uğur, Deniz
The growing prevalence of visual disinformation has become an important problem to solve nowadays. Cheapfake is a new term used for the altered media generated by non-AI techniques. In their recent COSMOS work, the authors developed a self-supervised training strategy that detected whether different captions for a given image were out-of-context, meaning that even though pointing to the same object(s) in the image, the captions implied different meanings. In this paper, we propose four methods to improve the detection accuracy of COSMOS. These methods range from differential sensing and fake-or-fact checking that detect contradicting or fake captions to object-caption matching and threshold adjustment that modify the baseline algorithm for improved accuracy.
Metadata only
Could head motions affect quality when viewing 360° videos?
(IEEE, 2023-04-01) Kara, Burak; Akçay, Mehmet Necmettin; Beğen, Ali Cengiz; Ahsan, S.; Curcio, I. D. D.; Aksu, E. B.; Computer Science; BEĞEN, Ali Cengiz; Kara, Burak; Akçay, Mehmet Necmettin
Measuring quality accurately and quickly (preferably in real time) when streaming 360° videos is essential to enhance the user experience. Most quality-of-experience metrics have primarily used viewport quality as a simple surrogate for such experiences at a given time. While this baseline approach has been later augmented by some researchers using pupil and gaze tracking, head tracking has not been considered in enough detail. This article tackles whether head motions can influence the perception of 360° videos. Inspired by the latest research, this article conceptualizes a head-motion-aware metric for measuring viewport quality. A comparative study against existing head-motion-unaware metrics reveals sizeable differences. Motivated by this, we invite the community to research this topic further and substantiate the new metric's validity.
Metadata only
Data-driven bandwidth prediction models and automated model selection for low latency
(IEEE, 2021) Bentaleb, A.; Beğen, Ali Cengiz; Harous, S.; Zimmermann, R.; Computer Science; BEĞEN, Ali Cengiz
Today's HTTP adaptive streaming solutions use a variety of algorithms to measure the available network bandwidth and predict its future values. Bandwidth prediction, which is already a difficult task, must be more accurate when lower latency is desired due to the shorter time available to react to bandwidth changes, and when mobile networks are involved due to their inherently more frequent and potentially larger bandwidth fluctuations. Any inaccuracy in bandwidth prediction results in flawed adaptation decisions, which will in turn translate into a diminished viewer experience. We propose an Automated Model for Prediction (AMP) that encompasses techniques for bandwidth prediction and model auto-selection specifically designed for low-latency live steaming with chunked transfer encoding. We first study statistical and computational intelligence techniques to implement a suite of bandwidth prediction models that can work accurately under a broad range of network conditions, and second, we introduce an automated prediction model selection method. We confirm the effectiveness of our solution through trace-driven live streaming experiments.
Metadata only
A distributed approach for bitrate selection in HTTP adaptive streaming
(ACM, 2018) Bentaleb, A.; Beğen, Ali Cengiz; Harous, S.; Zimmermann, R.; Computer Science; BEĞEN, Ali Cengiz
Past research has shown that concurrent HTTP adaptive streaming (HAS) players behave selfishly and the resulting competition for shared resources leads to underutilization or oversubscription of the network, presentation quality instability and unfairness among the players, all of which adversely impact the viewer experience. While coordination among the players, as opposed to all being selfish, has its merits and may alleviate some of these issues. A fully distributed architecture is still desirable in many deployments and better reflects the design spirit of HAS. In this study, we focus on and propose a distributed bitrate adaptation scheme for HAS that borrows ideas from consensus and game theory frameworks. Experimental results show that the proposed distributed approach provides significant improvements in terms of viewer experience, presentation quality stability, fairness and network utilization, without using any explicit communication between the players.

Browse

Browsing by Institution Author "BEĞEN, Ali Cengiz"