Audio Track from Ogg Video File Doesn't Play

My AudioSource doesn't seem to play the audio track from video files.

I can drop a regular audio file like an MP3 onto it, and it plays fine in play mode, so it's not a volume or AudioListener issue.

When I use the audio track of a movie file, whether from script by assigning the "audioClip" property of the MovieTexture to the "clip" of the AudioSource and then calling Play() on it, or by manually moving the "audio" clip from the .OGG movie file to the "clip" part of the AudioListener in the inspector with "Play On Awake" and "loop" checked, it's silent.

One can play the .OGG video in the Preview panel of the inspector, and hear sound fine together with the video, so the file is okay.

Thoughts?

I'm using 5.2 Pro.