In this paper we focus on wireless multimedia communication and investigate how soft information from the physical layer can be used at the application layer. The soft information yields reliability measures for the received bits and is incorporated into two soft input iterative JPEG2000 image decoders. These decoders use the soft information together with the error detection mechanisms in JPEG2000. When errors occur the decoders can increase the image quality and minimize the negative effect of error concealment without making time consuming retransmissions. Experiment results with images transmitted over a simulated wireless channel show that a simple decoding algorithm that utilizes soft information can give high gains in image quality. Only marginally higher gains are observed with a more complex decoding algorithm

Error free transmission is not always possible in todays nor future's communication networks without making retransmissions. Retransmissions, however, introduce delay. To delay sensitive applications the concept of soft information, i.e. lower layer knowledge about the channel conditions, could reduce the number of retransmissions. This paper explores the utilization of soft information in image decoding. It is not sufficient to treat the soft information and the image decoder separately. By combining soft information and error resilience in the decoder the image quality can be improved. Two modified JPEG2000 image decoders that utilize soft information have been developed. Experiment results with images transmitted over a simulated wireless channel show that a simple decoding process which utilizes soft information can give high gains in image quality. Only marginally higher gains are observed with a more complex decoding process

This paper explores the utilization of soft information in image decoding. Error free transmission is not always possible in today's nor future's communication networks without retransmissions. Retransmissions, however, introduce delay. To delay sensitive applications the concept of soft information, i.e. lower layer knowledge about the channel conditions, could reduce the number of retransmissions. It is not sufficient to treat the soft information and the image decoder separately. By combining soft information and the knowledge of the image structure in the decoding process image quality can be improved. A modified JPEG2000 image decoder that utilizes soft information has been developed. Experimental results with images transmitted over a simulated wireless channel show that iterative decoding with soft information can give high gains in image quality.

Detta magisterarbete redovisar den nya bildkodningsstandarden JPEG2000. Grundläggande egenskaper i standarden som exempelvis förlustfri och förlustlös kompression och kodning av intresseregioner förklaras. I JPEG2000 används waveletkodning för att uppnå en hög komprimeringskvot. Principen för waveletkodning av signaler redovisas och kodningsförfarandet i den nya standarden beskrivs mer grundligt. Fokus i detta arbete ligger på robusthetsmekanismerna i den nya standarden. Mekanismerna utvärderas genom tester med olika feldistributioner och med olika konfigurationer på en befintlig implementation av JPEG2000-standarden. Testerna visar att kodarens mekanismer klarar av att upptäcka bit- och skurfel. Dessa tester visar vidare att på grund av den wavelettransformering som utförs i JPEG2000-kodaren, och hur datan sedan placeras i bitströmmen, kan dataförluster tillåtas, men på en bekostnad av den visuella bildkvaliteten.