Given that it isn't affected by braking then I'd say it isn't, but geez it sounded like metal-on-disc.
It's got me then. The CV boots look like they're in good nick. If something had gotten in to the bearing it could make a noise but that's a strange sound for a bearing unless it's completely shot.
How's the wheel feel when you grab it from outside, top and bottom of the wheel, and push-pull to see if there's any vertical wobble? If there's play there, the bearings are shot.