iOS avfvideosrc resolution

[Eddie Kämpe]

Update: I found all valid resolutions, which can be derived from these constants.

let AVCaptureSessionPresetPhoto: String
let AVCaptureSessionPresetHigh: String
let AVCaptureSessionPresetMedium: String
let AVCaptureSessionPresetLow: String
let AVCaptureSessionPreset320x240: String
let AVCaptureSessionPreset352x288: String
let AVCaptureSessionPreset640x480: String
let AVCaptureSessionPreset960x540: String
let AVCaptureSessionPreset1280x720: String
let AVCaptureSessionPresetiFrame960x540: String
let AVCaptureSessionPresetiFrame1280x720: String

Link to Apple's documentation:
https://developer.apple.com/library/mac/documentation/AVFoundation/Reference/AVCaptureSession_Class/index.html#//apple_ref/doc/constant_group/Video_Input_Presets​