A fantastic 2001 documentary, with a huge chunk exploring Vermeer's compositional methods and techniques. Narrated by Meryl Streep.
It's obvious that Vermeer played around with a camera obscura, but the more likely explanation is that he became so familiar with its optical distortion that he 'became' a camera obscura (he adopted its way of seeing as his aesthetic).
The placement of his pointillist highlights on the bread in the Milkmaid (for example) is like a how a camera obscura would place highlights on a highly reflective object, but NEVER a loaf of bread. He placed them there because he was creating it in his imagination to look how shinier objects would look through a camera obscura, because he consciously enjoyed the effect of it and created it thus.
If Vermeer were dependent on a bulky optical device he would never have painted the View of Delft -- a massive outdoor landscape scene that was certainly created at home. It was generally impossible before the advent of tubed paint to work alla prima outside, and if the camera obscura were a trade secret he would have never have risked using it in public. Vermeer worked it up (along with the 'Little Street') from drawings and returned to the studio to make it.
Vermeer painted all of his interiors in the same room of his small house in Delft, yet the windows, the floor, the walls etc. always look different. Why? Because he was creating them in his head to look like a camera obscura, but not slavishly with a camera obscura.
Finally, X rays of Vermeer's paintings show that he reworked the placement of things over and over - meaning he was building from imagination, not directly from an optical device.