The event takes place:

Andreas Rossholm's public defence of a doctoral...

Welcome to attend Andreas Rossholm's public defence of a doctoral thesis at the Department of Applied Signal Processing, Blekinge Institute of Technology.

Time: Friday, November 28, at 13.15
Place: J1640, Campus Gräsvik, Karlskrona

Thesis title: On Enhancement and Quality Assessment of Audio and Video in Communication Systems

Research education subject: Applied Signal Processing

Faculty examiner: Dr Xing Danielsson Fan, Axis Communications

Examining committee :
Professor Haibo Li, KTH
Professor Ulrich Reiter, FH Köln
Dr. Bengt Mandersson, LTH

Deputy member: Professor Lars Lundberg, BTH

Chairperson: Dr. Benny Lövström, BTH

Principal supervisor: Professor Ingvar Claesson, BTH
Supervisor: Dr. Benny Lövström, BTH

The Department of Applied Signal Processing is hosting a reception after the seminar. Please respond to Tobias Ericson ( no later than November 21 if you intend to participate and kindly note if you have any food allergies etc.

The thesis is available at:!OpenDocument

The use of audio and video communication has increased exponentially over the last decade. As the use becomes more widespread so too does the demand for new functionalities and high quality. For many mobile devices with limited memory and computational power this has proven to be a challenge resulting in many innovative solutions and a number of new standards. Despite this, there is often a requirement for additional enhancement to improve quality. However, the quality as such is also of interest both from the objective quantity point of view as how it is perceived. The focus of this thesis work has been to perform enhancement within audio and speech encoding and video decoding, to measure impacting factors of audio and video performance, and to build methods to evaluate the perceived quality. The audio enhancement part of this thesis addresses the well known problem in the GSM system with an interfering signal generated by the switching nature of TDMA cellular telephony. Two different solutions are given to suppress such interference internally in the mobile handset. The first method involves the use of subtractive noise cancellation employing correlators, the second uses a structure of IIR noth filters. Both solutions use control algorithms based on the state of the communication between the mobile handsetand the base station.The video enhancement part presents two post-filters. These two filters aredesigned to improve visual quality of highly compressed video streams from standard, blockbased video codecs by combating both blocking and ringing artifacts. The second postfilter also performs sharpening. The third part addresses the problem of measuring audio and video delay aswell the skewness between these, also known as synchronization. This methodis a black box method enabling measurement on any application and platformunder any network conditions. The last part addresses no-reference (NR) bitstream video quality prediction using features extracted from the coded video stream. Several method have been evaluated and used, Multiple Linear Regression (MLR), Artificial Neural Network (ANN), and Least Square Support Vector Machines (LS-SVM),showing high correlation with both MOS and objective video assessment methods as PSNR and PEVQ. Also has the trade of and impact from temporal, spatial and quantization variations on perceptual video quality has been analysed.

Organizer, personal / school / organizer:
Department of Applied Signal Processing

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