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Proceedings Paper

Novel modes and adaptive block scanning order for intra prediction in AV1
Author(s): Ofer Hadar; Ariel Shleifer; Debargha Mukherjee; Urvang Joshi; Itai Mazar; Michael Yuzvinsky; Nitzan Tavor; Nati Itzhak; Raz Birman
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Paper Abstract

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.

Paper Details

Date Published: 19 September 2017
PDF: 10 pages
Proc. SPIE 10396, Applications of Digital Image Processing XL, 103960G (19 September 2017); doi: 10.1117/12.2274035
Show Author Affiliations
Ofer Hadar, Ben-Gurion Univ. of the Negev (Israel)
Ariel Shleifer, Ben-Gurion Univ. of the Negev (Israel)
Debargha Mukherjee, Google, Inc. (United States)
Urvang Joshi, Google, Inc. (United States)
Itai Mazar, Ben-Gurion Univ. of the Negev (Israel)
Michael Yuzvinsky, Ben-Gurion Univ. of the Negev (Israel)
Nitzan Tavor, Ben-Gurion Univ. of the Negev (Israel)
Nati Itzhak, Ben-Gurion Univ. of the Negev (Israel)
Raz Birman, Ben-Gurion Univ. of the Negev (Israel)

Published in SPIE Proceedings Vol. 10396:
Applications of Digital Image Processing XL
Andrew G. Tescher, Editor(s)

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