With the preferred languages for audio and subtitle, you can enjoy a video with the set language directly when playing a video with multi track.
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Go to Settings and tap Audio.

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Tap Preferred Languages.

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The top is set to priority. You can add other languages with Add Languages….

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Select a language to add.

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You can also edit them to move the priority.

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Tap Audio in Settings button on the left side of playback screen after playing a video which has multi track audio.

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Go to Settings and tap Subtitle.

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Tap Preferred Languages.

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Set the preferred languages for subtitle.

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The subtitle track is played in the language you set.