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A preprocessing approach to ROI Video Coding using Variable Gaussian Filters and Variance in Intensity
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. (Realistic3D, SensibleReality, MUCOM)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. (Realistic3D, SensibleReality, MUCOM)
Responsible organisation
2005 (English)In: Proceedings Elmar - International Symposium Electronics in Marine, Zagreb, Croatia: IEEE conference proceedings, 2005, 65-68 p., 1505643Conference paper, (Refereed)
Abstract [en]

In applications involving video over mobile phones or Internet, the limited quality depending on the transmission rate can be further improved by region-of-interest (ROI) coding. In this paper we present a preprocessing method using variable Gaussian filters controlled by a quality map indicating the distance to the ROI border that seeks to smooth the border effects between ROI and non-ROI. According to subjective tests the reduction of border effects increases the percieved quality, compared to using only one low pass filter. It also introduces a small improvement of the PSNR of the intensity component within the ROI after compression. With the compressed original sequence as a reference, the average PSNR was increased by 1.25 dB and 2.3 dB for 100 kbit/s and 150 kbit/s, respectively. Furthermore, in order to reduce computational complexity, a modified quality map is introduced using variance in intensity to exclude pixels, which are not visibly affected by the Gaussian filters. No change in quality is noticed when using less than 76% of the pixels.

Place, publisher, year, edition, pages
Zagreb, Croatia: IEEE conference proceedings, 2005. 65-68 p., 1505643
Series
Proceedings Elmar - International Symposium Electronics in Marine, ISSN 1334-2630
Keyword [en]
Region of interest, ROI, variable gaussian filters, variance
National Category
Computer Science
Identifiers
URN: urn:nbn:se:miun:diva-5795ISI: 000234256900016Scopus ID: 2-s2.0-33745257601Local ID: 3198ISBN: 953-7044-04-1 (print)OAI: oai:DiVA.org:miun-5795DiVA: diva2:30828
Conference
Elmar 2005 - 47th International Symposium Electronics in Marine; Zadar; Croatia; 8 June 2005 through 10 June 2005
Projects
STC - Sensible Things that Communicate
Available from: 2008-09-30 Created: 2009-07-30 Last updated: 2016-09-28Bibliographically approved
In thesis
1. Spatio-Temporal Pre-Processing Methods for Region-of-Interest Video Coding
Open this publication in new window or tab >>Spatio-Temporal Pre-Processing Methods for Region-of-Interest Video Coding
2007 (English)Licentiate thesis, monograph (Other academic)
Abstract [en]

In video transmission at low bit rates the challenge is to compress the video with a minimal reduction of the percieved quality. The compression can be adapted to knowledge of which regions in the video sequence are of most interest to the viewer. Region of interest (ROI) video coding uses this information to control the allocation of bits to the background and the ROI. The aim is to increase the quality in the ROI at the expense of the quality in the background. In order for this to occur the typical content of an ROI for a particular application is firstly determined and the actual detection is performed based on this information. The allocation of bits can then be controlled based on the result of the detection.

In this licenciate thesis existing methods to control bit allocation in ROI video coding are investigated. In particular pre-processing methods that are applied independently of the codec or standard. This makes it possible to apply the method directly to the video sequence without modifications to the codec. Three filters are proposed in this thesis based on previous approaches. The spatial filter that only modifies the background within a single frame and the temporal filter that uses information from the previous frame. These two filters are also combined into a spatio-temporal filter. The abilities of these filters to reduce the number of bits necessary to encode the background and to successfully re-allocate these to the ROI are investigated. In addition the computational compexities of the algorithms are analysed.

The theoretical analysis is verified by quantitative tests. These include measuring the quality using both the PSNR of the ROI and the border of the background, as well as subjective tests with human test subjects and an analysis of motion vector statistics.

The qualitative analysis shows that the spatio-temporal filter has a better coding efficiency than the other filters and it successfully re-allocates the bits from the foreground to the background. The spatio-temporal filter gives an improvement in average PSNR in the ROI of more than 1.32 dB or a reduction in bitrate of 31 % compared to the encoding of the original sequence. This result is similar to or slightly better than the spatial filter. However, the spatio-temporal filter has a better performance, since its computational complexity is lower than that of the spatial filter.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden Univ, 2007. 112 p.
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 21
Keyword
Region-of-interest, video coding, pre-processing, spatio-temporal filters
National Category
Information Science
Identifiers
urn:nbn:se:miun:diva-51 (URN)5113 (Local ID)978-91-85317-45-5 (ISBN)5113 (Archive number)5113 (OAI)
Presentation
2007-04-27, L111, L, Mittuniversitetet, Sundsvall, 13:00 (English)
Opponent
Supervisors
Available from: 2007-12-20 Created: 2007-12-20 Last updated: 2010-06-11Bibliographically approved

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