[EN] This Thesis presents a set of tools that allows the improvement of the digital video coding efficiency by exploiting the fundamentals of the state of the art video coding standards. This work has been focused both on research and on the application of the results to the encoding of digital video in real time mobile environments. The first contribution is an automatic shot change detection algorithm integrated in the encoding process. This algorithm is based on the monitoring of the coding mode of the macroblocks of the sequence, and the proper definition of a set of parameters provides excellent detection rates, precision and recall. The results also indicate an improvement on the encoded video quality when these detection techniques are used, which triggers the definition of a content-based keyframe selection algorithm. With this method, the optimal position of reference pictures can be determined. These keyframes are then used by the encoder to perform temporal prediction of the subsequent frames, which improves the compression rate and the encoded video quality (both objective and subjective). This quality improvement is the main objective of this Thesis. In the last part of this work, a rate control algorithm for variable bitrate and frame rate environments has been defined, being able to generate a bitstream that quickly follows the varying conditions of the mobile channel. In parallel to all this work, a set of training and test sequences has been obtained, providing an optimal environment for the design, development, configuration, optimization and test of the algorithms described here. / [ES] Esta tesis presenta un conjunto de herramientas que permiten mejorar la eficiencia de codificación de vídeo mediante la explotación de los fundamentos en los que se basan los principales estándares de codificación actuales. El trabajo se ha orientado tanto a la investigación como a la aplicación de los resultados a la codificación de vídeo en tiempo real en entornos móviles. En primer lugar se ha definido un algoritmo de detección automática de cambios de plano para entornos de tiempo real integrado en el proceso de codificación. Este algoritmo está basado en la monitorización del modo de codificación de los macrobloques de la secuencia y la correcta definición de un conjunto de parámetros consigue unas tasas de detección, una precisión y una eficacia superiores a otros métodos similares existentes en la literatura. Los resultados muestran también una mejora en la calidad del vídeo codificado al aplicar estas técnicas de detección, lo que lleva a la definición de un algoritmo de selección de imágenes de referencia (keyframes) basado en el contenido. Así se pueden obtener las posiciones óptimas para las imágenes de referencia utilizadas por el codificador para realizar predicciones temporales que aumentan la calidad tanto objetiva como subjetiva del vídeo codificado, lo que constituye a su vez el objetivo principal de esta tesis. Por último, se ha diseñado un algoritmo de control de tasa capaz de obtener un bitstream que se adapta rápidamente a los cambios tanto de bitrate como de tasa de imágenes por segundo producidos en el canal móvil. Paralelamente, se ha obtenido un conjunto de secuencias de entrenamiento y test que proporcionan un entorno óptimo para el diseño, desarrollo, configuración, optimización y prueba de los algoritmos aquí descritos. / [CAT] Aquesta tesi presenta un conjunt de ferramentes que permeten millorar la eficiència de codificació de vídeo digital mitjançant l'explotació dels fonaments en els que es basen els principals estàndards de codificació actuals. El treball ha estat orientat tant a la investigació com a l'aplicació dels resultats a la codificació de vídeo en temps real en entorns mòbils. En primer lloc s'ha definit un algoritme de detecció automàtica de canvis de plànol integrat en el propi procés de codificació. Aquest algoritme s'ha basat en la monitorització del mode de codificació dels macroblocs de la seqüència, i la correcta definició d'un conjunt de paràmetres de configuració permet aconseguir unes taxes de detecció, una precisió i una eficàcia superiors a altres mètodes similars presents a la literatura. Aquests resultats també indiquen una millora en la qualitat del vídeo codificat al aplicar aquestes tècniques de detecció la qual ens porta a la definició d'un algoritme de selecció d'imatges de referència (keyframes) basada en el contingut. Amb aquest algoritme es poden obtenir les posicions òptimes per a les imatges de referència utilitzades pel codificador per a realitzar prediccions temporals òptimes que augmenten la qualitat tant objectiva com subjectiva del vídeo codificat. Amb esta millora s'assoleix l'objectiu principal d'aquesta tesi. Per últim, s'ha dissenyat un algoritme de control de taxa capaç d'obtenir un bitstream que s'adapta ràpidament als canvis tant de bitrate com de taxa d'imatges per segon requerits per les condicions canviants del canal mòbil. Paral·lelament s'ha obtingut un conjunt de seqüències d'entrenament i test que permet disposar d'un entorn òptim per al disseny, desenvolupament, configuració, optimització i prova dels algoritmes descrits en aquestes fulles. / Usach Molina, P. (2015). TÉCNICAS DE MEJORA DE LA EFICIENCIA DE CODIFICACIÓN DE VÍDEO [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59446 / TESIS

This thesis explores possible solutions to replace Adobe Flash Player by using toolsalready built into modern web browsers, and explores the tradeoffs between bitrate, qual-ity, and delay when using an adaptive bitrate for live streamed video. Using an adaptivebitrate for streamed video was found to reduce stalls in playback for the client by adapt-ing to the available bandwidth. A newer codec can further compress the video file sizewhile maintaining the same video quality. This can improve the viewing experience forclients on a restricted or a congested network. The tests conducted in this thesis showthat producing an adaptive bitrate stream and changing codecs is a very CPU intensiveprocess.

Severe weather impacts life and in this dire condition, people rely on communication, to organize relief and stay in touch with their loved ones. In such situations, cellular network infrastructure\footnote{We refer to cellular network infrastructure as infrastructure for the entirety of this document} might be affected due to power outage, link failures, etc. This urges us to look at Ad-hoc mode of communication, to offload major traffic partially or fully from the infrastructure, depending on the status of it. We look into threefold approach, ranging from the case where the infrastructure is completely unavailable, to where it has been replaced by make shift low capacity mobile cellular base station. First, we look into communication without infrastructure and timely, dissemination of weather alerts specific to geographical areas. We look into the specific case of floods as they affect significant number of people. Due to the nature of the problem we can utilize the properties of Information Centric Networking (ICN) in this context, namely: i) Flexibility and high failure resistance: Any node in the network that has the information can satisfy the query ii) Robust: Only sensor and car need to communicate iii) Fine grained geo-location specific information dissemination. We analyze how message forwarding using ICN on top of Ad hoc network, approach compares to the one based on infrastructure, that is less resilient in the case of disaster. In addition, we compare the performance of different message forwarding strategies in VANETs (Vehicular Adhoc Networks) using ICN. Our results show that ICN strategy outperforms the infrastructure-based approach as it is 100 times faster for 63\% of total messages delivered. Then we look into the case where we have the cellular network infrastructure, but it is being pressured due to rapid increase in volume of network traffic (as seen during a major event) or it has been replaced by low capacity mobile tower. In this case we look at offloading as much traffic as possible from the infrastructure to device-to-device communication. However, the host-oriented model of the TCP/IP-based Internet poses challenges to this communication pattern. A scheme that uses an ICN model to fetch content from nearby peers, increases the resiliency of the network in cases of outages and disasters. We collected content popularity statistics from social media to create a content request pattern and evaluate our approach through the simulation of realistic urban scenarios. Additionally, we analyze the scenario of large crowds in sports venues. Our simulation results show that we can offload traffic from the backhaul network by up to 51.7\%, suggesting an advantageous path to support the surge in traffic while keeping complexity and cost for the network operator at manageable levels. Finally, we look at adaptive bit-rate streaming (ABR) streaming, which has contributed significantly to the reduction of video playout stalling, mainly in highly variable bandwidth conditions. ABR clients continue to suffer from the variation of bit rate qualities over the duration of a streaming session. Similar to stalling, these variations in bit rate quality have a negative impact on the users’ Quality of Experience (QoE). We use a trace from a large-scale CDN to show that such quality changes occur in a significant amount of streaming sessions and investigate an ABR video segment retransmission approach to reduce the number of such quality changes. As the new HTTP/2 standard is becoming increasingly popular, we also see an increase in the usage of HTTP/2 as an alternative protocol for the transmission of web traffic including video streaming. Using various network conditions, we conduct a systematic comparison of existing transport layer approaches for HTTP/2 that is best suited for ABR segment retransmissions. Since it is well known that both protocols provide a series of improvements over HTTP/1.1, we perform experiments both in controlled environments and over transcontinental links in the Internet and find that these benefits also “trickle up” into the application layer when it comes to ABR video streaming where HTTP/2 retransmissions can significantly improve the average quality bitrate while simultaneously minimizing bit rate variations over the duration of a streaming session. Taking inspiration from the first two approaches, we take into account the resiliency of a multi-path approach and further look at a multi-path and multi-stream approach to ABR streaming and demonstrate that losses on one path have very little impact on the other from the same multi-path connection and this increases throughput and resiliency of communication.

The diploma thesis deals with analysis and modeling of power line communication using NS-3. The introduction part summarizes basic information about PLC technology, distribution grids, and broadband standards. This is followed by the analysis of the transmission line and modulation method. Furthermore, the simulation tool and possibilities of its extension are described. The influence of different cross-section and type of line on channel capacity is examined in the practical part of this paper. The influence of repeaters on bitrate is examined as well. The medium-voltage line was implemented and further scenarios dealing with bitrate or optimal level of noise. The focus of the last part is to find the repeaters on the path and to determine the capacity and bitrate on the path of the large topology.

In a video there are certain regions in the image that viewers focus on more than others, which are called the salient regions or Regions­Of-Interest (ROI). This thesis aims to improve the perceived quality of videos by improving the quality of these ROis while degrading the quality of the other non-ROI regions of a frame to keep the same bitrate as would have been the case otherwise. This improvement is achieved by using saliency maps generated using an eye tracker or a deep neural network and providing this information to a modified video encoder. In this thesis the open source x264 encoder was chosen to make use of this information. The effects of ROI encoding are studied for high quality 720p videos by encoding them at low bitrates. The results indicate that ROI encoding can improve subjective video quality when carefully applied. / I en video £inns <let vissa delar av bilden som tittarna fokuserar mer pa an andra, och dessa kallas Region of Interest". Malet med den har upp­satsen ar att hoja den av tittaren upplevda videokvaliteten genom att minska kompressionsgraden ( och darmed hoja kvaliteten) i de iogon­fallande delarna av bilden, samtid som man hojer kompressionsgra­den i ovriga delar sa att bitraten blir den samma som innan andring­en. Den har forbattringen gors genom att anvanda Saliency Mapsss­om visar de iogonfallande delarna for varje bildruta. Dessa Saliency Maps"har antingen detekterats med hjalp av en Eye Tracker eller sa har de raknats fram av ett Neuralt Natverk. Informationen anvands sedan i en modifierad version av den oppna codecen x264 enligt en egen­designad algoritm. Effekten av forandringen har studerats genom att koda hogkvalitativa kallfiler vid lag bitrate. Resultaten indikerar att denna metod kan forbattra den upplevda kvaliteten av en video om den appliceras med ratt styrka.

<p>This thesis introduces a coding scheme for very low bitrate video coding through the aid of principal component analysis. Principal information of the facial mimic for a person can be extracted and stored in an Eigenspace. Entire video frames of this persons face can then be compressed with the Eigenspace to only a few projection coefficients. Principal component video coding encodes entire frames at once and increased frame size does not increase the necessary bitrate for encoding, as standard coding schemes do. This enables video communication with high frame rate, spatial resolution and visual quality at very low bitrates. No standard video coding technique provides these four features at the same time.</p><p>Theoretical bounds for using principal components to encode facial video sequences are presented. Two different theoretical bounds are derived. One that describes the minimal distortion when a certain number of Eigenimages are used and one that describes the minimum distortion when a minimum number of bits are used.</p><p>We investigate how the reconstruction quality for the coding scheme is affected when the Eigenspace, mean image and coefficients are compressed to enable efficient transmission. The Eigenspace and mean image are compressed through JPEG-compression while the while the coefficients are quantized. We show that high compression ratios can be used almost without any decrease in reconstruction quality for the coding scheme.</p><p>Different ways of re-using the Eigenspace for a person extracted from one video sequence to encode other video sequences are examined. The most important factor is the positioning of the facial features in the video frames.</p><p>Through a user test we find that it is extremely important to consider secondary workloads and how users make use of video when experimental setups are designed.</p>

Video is the most demanding modality from the viewpoints of bandwidth, computational complexity, and resolution. Thus, there has been limited progress in the field of mobile video technology. In the research, the focus is on elastic wireless video technology, and its adaptation to diagnostic application requirements in real-time clinical assessment. It is important and timely to apply wireless video technology to real-time remote diagnosis of emergent medical events. This premise comes from initial successes in telehealth based on wired networks. The enablement of mobility (for the physician and/or the patient) by wireless communication will be a next major step, but this advance will depend on definitive and compelling demonstrations of reliability. Thus, an important goal of the research is to develop a complete methodology that will be embraced by physicians. Acute pediatric asthma has been identified as a domain where this new capability will be highly welcome. The research uses flexible and interactive algorithms for Region-of-Interest (ROI) processing. ROI processing is a useful approach to achieve the optimal balance in the quality-bandwidth tradeoff characteristic of visual communication services. The notion of ROI has been traditionally used mostly for foreground-background separation in scene rendering and manipulation, and only more recently for variably quality compression. Even when the latter goal is considered, quality criteria have been ad-hoc and at best useful for video conferencing, given that the medical domain has its own fidelity criteria. The research thus focuses on the design of an elastic ROI-based compression paradigm with medical diagnosis as a central criterion. The research describes the methodology to achieve elasticity through rate control algorithms at the encoder. An elastic non-parametric approach is proposed that uses a priori user-specified video quality information, quantifies this information, and incorporates this into the encoder in the form of region-quality mappings. This method is compared to a parametric bit allocation approach that is based on region-features and a set of tuning weights. A number of videos of actual patients were filmed and used as the video database for the developed algorithms. In testing the elastic non-parametric and parametric algorithms, both objective measures in the form of Peak Signal to Noise Ratio (PSNR), and subjective evaluations were used. Thus, in this work, the focus is on domain relevance of the algorithms developed, as opposed to network related issues such as packet losses. This is justified in that these may have broader value with other applications, and continuation of this work will include realistic network conditions. To summarize, the research shows the usefulness of ROI processing as a means of achieving a gain (in a bits per pixel sense) over uniform compression at the same bitrate. It also shows how quantifying a notion of functionally lossless video quality diagnostically lossless video quality in a video-based telehealth system, in a bits per pixel sense is useful from an applications and bitrate perspective. Finally, a combination of these two concepts is advantageous i.e. diagnostically lossless ROI video quality is achievable over bitrate limited channels.

This thesis introduces a coding scheme for very low bitrate video coding through the aid of principal component analysis. Principal information of the facial mimic for a person can be extracted and stored in an Eigenspace. Entire video frames of this persons face can then be compressed with the Eigenspace to only a few projection coefficients. Principal component video coding encodes entire frames at once and increased frame size does not increase the necessary bitrate for encoding, as standard coding schemes do. This enables video communication with high frame rate, spatial resolution and visual quality at very low bitrates. No standard video coding technique provides these four features at the same time. Theoretical bounds for using principal components to encode facial video sequences are presented. Two different theoretical bounds are derived. One that describes the minimal distortion when a certain number of Eigenimages are used and one that describes the minimum distortion when a minimum number of bits are used. We investigate how the reconstruction quality for the coding scheme is affected when the Eigenspace, mean image and coefficients are compressed to enable efficient transmission. The Eigenspace and mean image are compressed through JPEG-compression while the while the coefficients are quantized. We show that high compression ratios can be used almost without any decrease in reconstruction quality for the coding scheme. Different ways of re-using the Eigenspace for a person extracted from one video sequence to encode other video sequences are examined. The most important factor is the positioning of the facial features in the video frames. Through a user test we find that it is extremely important to consider secondary workloads and how users make use of video when experimental setups are designed.

Examensarbetet bakom denna rapport utgör en undersökande studie om hur transmission av mediadata i nätverk kan göras effektivare. Det kan åstadkommas genom att viss tilläggsinformation avsedd för att jämna ut datatakten adderas i det realtidsprotokoll, Real Time Protocol, som används för strömmande media. Genom att försöka skicka lika mycket data under alla konsekutiva tidsintervall i sessionen kommer datatakten vid en godtycklig tidpunkt med större sannolikhet att vara densamma som vid tidigare klockslag. En streamingserver kan tolka, hantera och skicka data vidare enligt instruktionerna i protokollets sidhuvud. Datatakten jämnas ut genom att i förtid, under tidsintervall som innehåller mindre data, skicka även senare data i strömmen. Resultatet av detta är en utjämnad datataktskurva som i sin tur leder till en jämnare användning av nätverkskapaciteten. Arbetet inkluderar en översiktlig analys av beteendet hos strömmande media, bakgrundsteori om filkonstruktion och nätverksteknologier samt ett förslag på hur mediafiler kan modifieras för att uppfylla syftet med examensarbetet. Resultat och diskussion kan förhoppningsvis användas som underlag för en framtida implementation av en applikation ämnad att förbättra trafikflöden över nätverk.

A large portion of network resources is consumed by video traffic, and this increasing demand causes challenges in the area of video coding. As the expectations for high-quality video grow the required bitrate rises in accordance, which motivates research on lowering bitrates. This research investigated the question: How can genre-based video transcoding (using x265) be improved for animated Video On Demand-content, to maintain the subjective quality of the current profile at a lower bitrate? A transcoding profile for animated content was created with an improved motion estimation technique and an experimental change of AQ mode. A double-blind AB test was conducted where the users were exposed to 10 video pairs transcoded with the old and the new transcoding profile and chose their preference. 570 people participated. Results show that for most instances people barely saw any difference between the profiles, but a small difference in perceived quality for 2D and 3D content. Consequently, it appears that there is a potential for reducing the bitrate for animated content but further exploration is required to draw statistically significant conclusions. / En stor del av nätverksresurserna används till videotrafik, och denna ökande efterfrågan medför utmaningar inom området videkodning. När förväntningarna på högkvalitativ video ökar stiger den krävda bithastigheten i enlighet, vilket motiverar forskning kring låga bithastigheter. Denna forskning undersökte följande fråga: Hur kan genrebaserad videotranskodering (med hjälp av x265) förbättras för animerat Video On Demand-innehåll, för att bibehålla den subjektiva kvaliteten hos den nuvarande profilen med en lägre bithastighet? En transkoderingsprofil för animerat innehåll skapades med en förbättrad motion estimation-teknik och en experimentell förändring av AQ-läge. En dubbelblint AB-test genomfördes där användarna exponerades för 10 videopar transkoderade med den gamla och den nya profilen, och valde sin preferens. 570 personer deltog. Resultaten visade att för de flesta instanserna såg deltagarna knappt någon skillnad mellan profilerna, men en viss skillnad i upplevd kvalitet för 2D- och 3D-material. Följaktligen verkar det som om det finns potential att minska bithastigheten för animerat innehåll, men att detta måste undersökas ytterligare för att dra statistiskt signifikanta slutsatser.