Seminario sullo Standard MPEG-4: utilizzo ed aspetti implementativi

Una delle tecnologie chiave che hanno permesso il grande sviluppo della televisione digitale è la compressione video. La tecnologia di codifica video nota come MPEG-2, sviluppata nei primi anni novanta, è diventata lo standard di trasmissione DTV (Digital TV) sia satellitare sia terrestre in quasi tutti i paesi del mondo. Da allora la velocità dei microprocessori e le capacità di memoria dei dispositivi hardware per la codifica e la decodifica sono migliorate significativamente rendendo possibile lo sviluppo e l’implementazione di algoritmi di codifica innovativi in grado di abbattere significativamente i limiti di compressione dello standard MPEG-2. Tali innovazioni, sfociate nel 2003 nello standard MPEG-4 AVC (Advanced Video Coding), non hanno permesso di mantenere la compatibilità all’indietro con l’MPEG-2, e questo ha inizialmente costituito un limite alla loro introduzione nei sistemi di trasmissione DTV. Tuttavia, negli ultimi anni la codifica MPEG-4 AVC si è diffusa rapidamente, è stata adottata dal progetto DVB, recentemente dall’ATSC, ed è lo standard di codifica nell’IPTV. L’obiettivo di questo seminario, che si articola in due giornate, è quello di presentare lo standard di codifica MPEG-4 AVC con particolare attenzione agli aspetti implementativi del livello di codifica video.2008-11-18Sardegna Ricerche, Edificio 2, Località Piscinamanna 09010 Pula (CA) - ItaliaSeminario sullo Standard MPEG-4: utilizzo ed aspetti implementativ

VHDL Modeling of an H.264/AVC Video Decoder

Transmission and storage of video data has necessitated the development of video com pression techniques. One of today\u27s most widely used video compression techniques is the MPEG-2 standard, which is over ten years old. A task force sponsored by the same groups that developed MPEG-2 has recently finished defining a new standard that is meant to replace MPEG-2 for future video compression applications. This standard, H.264/AVC, uses significantly improved compression techniques. It is capable of providing similar pic ture quality at bit rates of 30-70% less than MPEG-2, depending on the particular video sequence and application [20]. This thesis developed a complete VHDL behavioral model of a video decoder imple menting the Baseline Profile of the H.264/AVC standard. The decoder was verified using a testing environment for comparison with reference software results. Development of a synthesizable hardware description was also shown for two components of the video de coder: the transform unit and the deblocking filter. This demonstrated how a complete video decoder could be developed one module at a time with individual module verifica tion. Analysis was also done to estimate the performance and hardware requirements for a complete implementation on an FPGA device

Reduction of blocking artifacts using side information

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 95-96).Block-based image and video coding systems are used extensively in practice. In low bit-rate applications, however, they suffer from annoying discontinuities, called blocking artifacts. Prior research shows that incorporating systems that reduce blocking artifacts into codecs is useful because visual quality is improved. Existing methods reduce blocking artifacts by applying various post-processing techniques to the compressed image. Such methods require neither any modification to current encoders nor an increase in the bit-rate. This thesis examines a framework where blocking artifacts are reduced using side information transmitted from the encoder to the decoder. Using side information enables the use of the original image in deblocking, which improves performance. Furthermore, the computational burden at the decoder is reduced. The principal question that arises is whether the gains in performance of this choice can compensate for the increase in the bit-rate due to the transmission of side information. Experiments are carried out to answer this question with the following sample system: The encoder determines block boundaries that exhibit blocking artifacts as well as filters (from a predefined set of filters) that best deblock these block boundaries.(cont.) Then it transmits side information that conveys the determined block boundaries together with their selected filters to the decoder. The decoder uses the received side information to perform deblocking. The proposed sample system is compared against an ordinary coding system and a post-processing type deblocking system with the bit-rate of these systems being equal to the overall bit-rate (regular encoding bits + side information bits) of the proposed system. The results of the comparisons indicate that, both for images and video sequences, the proposed system can perform better in terms of both visual quality and PSNR for some range of coding bit-rates.by Fatih Kamisli.S.M

Spatially Scalable Video Coding (SSVC) Using Motion Compensated Recursive Temporal Filtering (MCRTF)

Through the following years, streaming makers will be progressively tasked supplying enhanced streams of video to gadgets as mobile phones and set top boxes, alongside diverse quality variants for clients to get content on general Internet. While there have been various ways to deal with this issue, including different bit rate feature, one exceptionally solid competitor will be a H.264 expansion called Scalable Video Coding ( SVC). It encodes video into "layers," beginning with the "base" layer, which contains the most minimal information of the bit-stream, and then moving towards “enhanced layers” which includes the information to scale up the output. Also SVC gives support for different resolutions inside a single compressed bit stream which is known as spatial scalabilility. In this thesis a problem on SSVC has been addressed. The video sequences had been made scalable in spatial domain. In order to make it more efficient for real time applications, motion compensated recursive temporal filtering (MCRTF) has been implemented. This scheme enhances the efficiency of the components of a visual signal. The temporal filter used here helps in reducing noisearising from the plurality of the frames and the improvised output with reduced noise is used in the process of predictive encoding. Also it eliminates the inherent drift, which arises due to difference between encoder and decoder. As visual signals are always subjected to temporal correlation, motion compensation from the adjacent frames and using it as the reference during the process of predictive coding is of prior importance. The conventional and the proposed method have been used during the encoding process of various video sequences in the spatial domain and an analytical study on that has been carried ou