This paper describes a comprehensive study on the sound quality of the Opus codec for stereo, surround, and immersive audio formats for music and cinematic content. We conducted three listening tests on Opus encoded stereo, 5.1 and 7.1.4 channel content taken from music, cinematic, and EBU files encoded at bitrates of 32, 48, and 64 kbps per channel. Current Opus encapsulation in Ogg does not support 7.1.4 with stereo pairing. Hence, we propose a new stereo pairing schema to accommodate 7.1.4 content in Opus with joint stereo encoding. Results indicate that a bitrate of 64 kbps per channel or higher is required for transparency in stereo, but 48 kbps per channel may be sufficient for 5.1 and 7.1.4 audio formats.
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