Contributions to reconfigurable video coding and low bit rate video coding

In this PhD Thesis, two different issues on video coding are stated and their corresponding proposed solutions discussed. In the first place, some problems of the use of video coding standards are identi ed and the potential of new reconfigurable platforms is put to the test. Specifically, the proposal from MPEG for a Reconfigurable Video Coding (RVC) standard is compared with a more ambitious proposal for Fully Configurable Video Coding (FCVC). In both cases, the objective is to nd a way for the definition of new video codecs without the concurrence of a classical standardization process, in order to reduce the time-to-market of new ideas while maintaining the proper interoperability between codecs. The main difference between these approaches is the ability of FCVC to reconfigure each program line in the encoder and decoder definition, while RVC only enables to conform the codec description from a database of standardized functional units. The proof of concept carried out in the FCVC prototype enabled to propose the incorporation of some of the FCVC capabilities in future versions of the RVC standard. The second part of the Thesis deals with the design and implementation of a filtering algorithm in a hybrid video encoder in order to simplify the high frequencies present in the prediction residue, which are the most expensive for the encoder in terms of output bit rate. By means of this filtering, the quantization scale employed by the video encoder in low bit rate is kept in reasonable values and the risk of appearance of encoding artifacts is reduced. The proposed algorithm includes a block for filter control that determines the proper amount of filtering from the encoder operating point and the characteristics of the sequence to be processed. This filter control is tuned according to perceptual considerations related with overall subjective quality assessment. Finally, the complete algorithm was tested by means of a standard subjective video quality assessment test, and the results showed a noticeable improvement in the quality score with respect to the non-filtered version, confirming that the proposed method reduces the presence of harmful low bit rate artifacts

A Rate Control Algorthm for Low-Delay H.264 Video Coding with Stored-B Pictures

A rate control (RC) algorithm for H.264 video coding with stored-B (SB) pictures is proposed for low-delay applications. Different models for P and SB pictures are defined for a better QP and MAD estimation. Furthermore, a novel saw-tooth shaped model of target buffer level has also been introduced for a proper bit allocation in GOP structures with SB pictures. Our experimental results show that this proposal outperforms the reference software RC in terms of buffer occupancy and target bit rate adjustment at the expense of slight quality reduction.Publicad

Adaptive Multi-Pattern Fast Block-Matching Algorithm Based on Motion Classification Techniques

Motion estimation is the most time-consuming subsystem in a video codec. Thus, more efficient methods of motion estimation should be investigated. Real video sequences usually exhibit a wide-range of motion content as well as different degrees of detail, which become particularly difficult to manage by typical block-matching algorithms. Recent developments in the area of motion estimation have focused on the adaptation to video contents. Adaptive thresholds and multi-pattern search algorithms have shown to achieve good performance when they success to adjust to motion characteristics. This paper proposes an adaptive algorithm, called MCS, that makes use of an especially tailored classifier that detects some motion cues and chooses the search pattern that best fits to them. Specifically, a hierarchical structure of binary linear classifiers is proposed. Our experimental results show that MCS notably reduces the computational cost with respect to an state-of-the-art method while maintaining the qualityPublicad

A Cauchy-density-based rate controller for H.264/AVC in low-delay environments

The accuracy of the Cauchy probability density function for modeling of the discrete cosine transform coefficient distribution has already been proved for the frame layer of the rate control subsystem of a hybrid video coder. Nevertheless, in some specific applications operating in real-time low-delay environments, a basic unit layer is recommended in order to provide a good trade-off between quality and delay control. In this paper, a novel basic unit bit allocation for H.264/AVC is proposed based on a simplified Cauchy probability density function source modeling. The experimental results show that the proposed algorithm improves the average peak signal-to-noise ratio in 0.28 and 0.35 dB with respect to two well-known rate control schemes, while maintaining similar peak signal-to-noise ratio standard deviation and buffer occupancy evolution

A two-level sliding-window VBR controller for real-time hierarchical video coding

In this paper, a novel rate control algorithm for real-time VBR hierarchical video coding is proposed. The algorithm works at two levels that are called long- and short-term levels. The long-term level aims at ensuring that the bit count does not exceed the maximum allowed amount for a few-second long window. To this end, it considers a sliding window spanning several GOPs, which is shifted on a GOP basis. In doing so, it avoids the potentially sharp adjustments at the end of the GOP that usually happen in non-sliding approaches. The short-term level aims to provide a proper QP adaptation to fit the target bit budget, which is dictated by the long-term level. It also uses a sliding window, which in this case extends over one GOP. The proposed algorithm has been assessed in realistic conditions for a variety of video sequences. It has been compared to both a constant quality and CBR hierarchical approaches, showing an excellent performance in terms of both rate-distortion and PSNR variation

Cauchy-Density-Based Basic Unit Layer Rate Controller for H.264/AVC

The rate control problem has been extensively studied in parallel to the development of the different video coding standards. The bit allocation via Cauchy-density-based rate-distortion (R-D) modeling of the discrete cosine transform (DCT) coefficients has proved to be one of the most accurate solution at picture level. Nevertheless, in some specific applications operating in real-time low-delay environments, a basic unit (BU) layer is recommended in order to provide a good trade-off between picture quality and delay control. In this paper, a novel BU bit allocation for H.264/AVC is proposed based on a simplified Cauchy probability density function (PDF) source modeling. The experimental results are twofold: 1) the proposed rate control algorithm (RCA) achieves an average PSNR improvement of 0.28 dB respect to a well known BU layer RCA, while maintaining a similar buffer occupancy evolution; and 2) It achieves to notably reduce the buffer occupancy fluctuations respect to a well known picture layer RCA, while maintaining similar quality levels.Publicad

El plano de Cartagena, su ensanche y sus inmediaciones por Julián Sáez

[SPA]En ciertas ocasiones la investigación histórica proporciona documentos de gran valor, documentos cargados de información sobre una época. El análisis de un documento gráfico de una ciudad, del “plano de la ciudad”, ofrece numerosas características de la misma: la influencia de la topografía, la forma del tejido urbano, la naturaleza y complejidad del espacio público o privado, la presencia de edificaciones públicas, las condiciones de la edificación o la tipología edificatoria, etc. La presente comunicación tiene como objetivo analizar el contenido y los recursos de expresión gráfica del plano de Cartagena, su ensanche y sus inmediaciones realizado por Julián Sáez en 1912. En definitiva, permite aproximarse al modo de vida colectivo de la sociedad del momento. [ENG] Sometimes historical research gives documents of great value, documents that are full of information from a certain period of time. The analysis of a graphic document of a city, precisely the “plan of the city”, shows lots of its characteristics: the influence of the topography, the shape of the city fabric, the nature and complexity of the public and private spaces, the presence of public buildings, the condition or building types etc. In sum, it allows to approach to the collective way of life of the society of the time. The plan of Cartagena realized by Julian Sáez in 1912 at the request of the Cartagena City Council belongs to that kind of documents that are essential in order to understand a city in a certain period of time. The plan faithfully reflects the reality and it is a neat and accurate drawing done with great graphic quality

Perceptually-aware bilateral filtering for quality improvement in low bit rate video coding

Proceedings of: Picture Coding Symposium (PCS 2012). Krakow, Poland, May 7-9, 2012Perceptual coding has become of great interest in modern video coding due to the need for higher compression rates. Many previous works have been carried out to incorporate perceptual information to hybrid video encoders, either modifying the quantization parameter according to a certain perceptual resource allocation map or preprocessing video sequences for removing information that is not perceptually relevant. The first strategy is limited by the presence of blocking artifacts and the second one lacks of adaptation to video content. In this paper, a novel and simple approach is proposed, which performs a smart filtering prior to the encoding process preserving both the structural and motion information. The experiments prove that the use of proposed method implemented on an H.264 encoder significantly improves its perceptual quality for low bit rates.Publicad

Diferencias cinemáticas entre saltadores de altura nacionales y saltadores de altura internacionales

The purpose of this study was to establish reference values for various kinematic variables in high jump that allow us to determine an execution model of Spanish athletes and compare it with the technical model proposed in the bibliography. The best jump of the first 25 finalists in the 2009 Spanish indoor championship were analyzed (13 males: height = 1.89 ± 0.05 m, and jump performance = 2.10 ± 0.09 m; and 12 females: height = 1.69 ± 0.10 m, and jump performance = 1.73 ± 0.08 m). A total of 35 kinematic variables related to the run-up (last two steps of the approach run), takeoff, and bar clearance phases were analyzed. A photogrammetric 3D protocol (using three video cameras at 50 frames per second and a Direct Linear Transformation) was used to establish the athletes’ coordinates. The analysis and digitalization of the jumps were done using the Kwon 3D software. The results of the study show that the largest differences between Spanish high jumpers and the model found in the bibliography are found in the pre-jump phase (length, frequency, and speed of steps) and in the take-off phase with regard to the speed of the center of massEl objetivo del trabajo fue fijar valores de referencia en diferentes variables cinemáticas para la prueba de salto de altura que permitan establecer el modelo de ejecución de los atletas nacionales y compararlo con el modelo técnico que establece la bibliografía. Se analizó el mejor intento de 25 saltadores de altura finalistas en el Campeonato de España en pista cubierta 2009 (13 hombres, 1.89 ± 0.05 m de estatura y 2.10 ± 0.09 m de rendimiento, y 12 mujeres, 1.69 ± 0.10 m de estatura y 1.73 ± 0.08 m de rendimiento). Se calcularon un total de 35 variables biomecánicas correspondientes a las fases de ante-salto (dos últimos pasos de la carrera de aproximación), batida y paso del listón. Se utilizó fotogrametría 3D a través de tres cámaras de vídeo operando a 50 fotogramas por segundo y utilizando el algoritmo de Transformación Linear Directa para la determinación de las coordenadas del deportista. El análisis y digitalización de los saltos se realizó en el programa Kwon 3D. Los resultados de este estudio muestran que las mayores diferencias entre los valores en los saltadores y saltadoras españolas al compararlos con los saltadores de nivel internacional se producen durante la fase ante-salto (longitud, frecuencia, y velocidad del paso) y durante la fase de batida a nivel de velocidad del CMActividad Física y Deport

A simplified subjective video quality assessment method based on signal detection theory

Proceedings of: Picture Coding Symposium (PCS 2012). Krakow, Poland, May 7-9, 2012.A simplified protocol and associated metrics based on Signal Detection Theory (SDT) for subjective Video Quality Assessment (VQA) is proposed with the aim of filling the gap existing between the lack of discrimination abilities of objective quality estimates, specially when perceptually motivated processing methods are involved and the costly normative subjective quality tests. The proposed protocol employs a reduced number of assessors and provides a quality ranking of the methods being evaluated. It is intended for providing the rapid experimental turn around necessary for developing algorithms. We have validated our proposal performing the test on a well-known result for the video coding community: namely, that the inclusion of an in-loop deblocking filter provides a quality enhancement. The results obtained corroborate this fact. A software interface to design and administrate the test is also made publicly available.This work has been partially supported by the regional project CCG10-UC3M/TIC-5304 (Comunidad Autónoma de Madrid - UC3M) and by National Grant TEC2011-26807 of the Spanish Ministry of Science and Innovation.Publicad