Urvang Joshi
Authored Publications
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AN OVERVIEW OF CORE CODING TOOLS IN THE AV1 VIDEO CODEC
Adrian Grange
Andrey Norkin
Ching-Han Chiang
Hui Su
Jean-Marc Valin
Luc Trudeau
Nathan Egge
Paul Wilkins
Peter de Rivaz
Sarah Parker
Steinar Midtskogen
Thomas Davies
Zoe Liu
The Picture Coding Symposium (PCS) (2018)
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AV1 is an emerging open-source and royalty-free video compression format, which is jointly developed and finalized in early 2018 by the Alliance for Open Media (AOMedia) industry consortium. The main goal of AV1 development is to achieve substantial compression gain over state-of-the-art codecs while maintaining practical decoding complexity and hardware feasibility. This paper provides a brief technical overview of key coding techniques in AV1 along with preliminary compression performance comparison against VP9 and HEVC.
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Novel modes and adaptive block scanning order for intra prediction in AV1
Ofer Hadar
Ariel Shleifer
Itai Mazar
Michael Yuzvinsky
Nitzan Tavor
Nati Itzhak
Raz Birman
SPIE Optical Engineering + Applications, 10396 (2017), 10396 - 10396 - 10
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The demand for streaming video content is on the rise and growing exponentially. Networks bandwidth is very costly and therefore there is a constant effort to improve video compression rates and enable the sending of reduced data volumes while retaining quality of experience (QoE). One basic feature that utilizes the spatial correlation of pixels for video compression is Intra-Prediction, which determines the codec’s compression efficiency. Intra prediction enables significant reduction of the Intra-Frame (I frame) size and, therefore, contributes to efficient exploitation of bandwidth. In this presentation, we propose new Intra-Prediction algorithms that improve the AV1 prediction model and provide better compression ratios. Two (2) types of methods are considered: )1( New scanning order method that maximizes spatial correlation in order to reduce prediction error; and )2( New Intra-Prediction modes implementation in AVI. Modern video coding standards, including AVI codec, utilize fixed scan orders in processing blocks during intra coding. The fixed scan orders typically result in residual blocks with high prediction error mainly in blocks with edges. This means that the fixed scan orders cannot fully exploit the content-adaptive spatial correlations between adjacent blocks, thus the bitrate after compression tends to be large. To reduce the bitrate induced by inaccurate intra prediction, the proposed approach adaptively chooses the scanning order of blocks according to criteria of firstly predicting blocks with maximum number of surrounding, already Inter-Predicted blocks. Using the modified scanning order method and the new modes has reduced the MSE by up to five (5) times when compared to conventional TM mode / Raster scan and up to two (2) times when compared to conventional CALIC mode / Raster scan, depending on the image characteristics (which determines the percentage of blocks predicted with Inter-Prediction, which in turn impacts the efficiency of the new scanning method). For the same cases, the PSNR was shown to improve by up to 7.4dB and up to 4 dB, respectively. The new modes have yielded 5% improvement in BD-Rate over traditionally used modes, when run on K-Frame, which is expected to yield ~1% of overall improvement.
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Novel inter and intra prediction tools under consideration for the emerging AV1 video codec
Sarah Parker
Hui Su
Angie Chiang
Zoe Liu
Chen Wang
Emil Keyder
SPIE Optical Engineering + Applications, 10396 (2017), 10396 - 10396 - 13
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Google started the WebM Project in 2010 to develop open source, royalty-free video codecs designed specifically for media on the Web. The second generation codec released by the WebM project, VP9, is currently served by YouTube, and enjoys billions of views per day. Realizing the need for even greater compression efficiency to cope with the growing demand for video on the web, the WebM team embarked on an ambitious project to develop a next edition codec AV1, in a consortium of major tech companies called the Alliance for Open Media, that achieves at least a generational improvement in coding efficiency over VP9. In this paper, we focus primarily on new tools in AV1 that improve the prediction of pixel blocks before transforms, quantization and entropy coding are invoked. Specifically, we describe tools and coding modes that improve intra, inter and combined inter-intra prediction. Results are presented on standard test sets.
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Video coding mode decision as a classification problem
Rashad Jillani
Chiranjib Bhattacharya
Hari Kalva
RK Ramakrishnan
IS&T/SPIE Electronic Imaging, 7543 (2010), 7543 - 7543 - 8
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In this paper, we show that it is possible to reduce the complexity of Intra MB coding in H. 264/AVC based on a novel chance constrained classifier. Using the pairs of simple mean-variances values, our technique is able to reduce the complexity of Intra MB coding process with a negligible loss in PSNR. We present an alternate approach to address the classification problem which is equivalent to machine learning. Implementation results show that the proposed method reduces encoding time to about 20% of the reference implementation with average loss of 0.05 dB in PSNR.
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