AMBIQUAL - a full reference objective quality metric for ambisonic spatial audio

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Title: AMBIQUAL - a full reference objective quality metric for ambisonic spatial audio
Authors: Narbutt, Miroslaw
Allen, Andrew
Skoglund, Jan
Chinen, Michael
Hines, Andrew
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Date: 13-Sep-2018
Online since: 2019-05-15T09:01:35Z
Abstract: Streaming spatial audio over networks requires efficient encoding techniques that compress the raw audio content without compromising quality of experience. Streaming service providers such as YouTube need a perceptually relevant objective audio quality metric to monitor users' perceived quality and spatial localization accuracy. In this paper we introduce a full reference objective spatial audio quality metric, AMBIQUAL, which assesses both Listening Quality and Localization Accuracy. In our solution both metrics are derived directly from the B-format Ambisonic audio. The metric extends and adapts the algorithm used in ViSQOLAudio, a full reference objective metric designed for assessing speech and audio quality. In particular, Listening Quality is derived from the omnidirectional channel and Localization Accuracy is derived from a weighted sum of similarity from B-format directional channels. This paper evaluates whether the proposed AMBIQUAL objective spatial audio quality metric can predict two factors: Listening Quality and Localization Accuracy by comparing its predictions with results from MUSHRA subjective listening tests. In particular, we evaluated the Listening Quality and Localization Accuracy of First and Third-Order Ambisonic audio compressed with the OPUS 1.2 codec at various bitrates (i.e. 32, 128 and 256, 512kbps respectively). The sample set for the tests comprised both recorded and synthetic audio clips with a wide range of time-frequency characteristics. To evaluate Localization Accuracy of compressed audio a number of fixed and dynamic (moving vertically and horizontally) source positions were selected for the test samples. Results showed a strong correlation (PCC=0.919; Spearman=0.882 regarding Listening Quality and PCC=0.854; Spearman=0.842 regarding Localization Accuracy) between objective quality scores derived from the B-format Ambisonic audio using AMBIQUAL and subjective scores obtained during listening MUSHRA tests. AMBIQUAL displays very promising quality assessment predictions for spatial audio. Future work will optimise the algorithm to generalise and validate it for any Higher Order Ambisonic formats.
Funding Details: European Commission - European Regional Development Fund
Science Foundation Ireland
Type of material: Conference Publication
Publisher: IEEE
Copyright (published version): 2018 IEEE
Keywords: Virtual realitySpatial audioAmbisonicsAudio codingAudio compressionOpus codecMUSHRA
DOI: 10.1109/qomex.2018.8463408
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Language: en
Status of Item: Peer reviewed
Is part of: 2018 Tenth International Conference on Quality of Multimedia Experience (QoMEX)
Conference Details: The 2018 Tenth International Conference on Quality of Multimedia Experience (QoMex), Sardinia, Italy, 29 May- 1 June 2018
ISBN: 9781538626054
Appears in Collections:Computer Science Research Collection

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