title: AVAssetExportSession estimatedOutputFileLength throws exception: 'Invalid presetName'
body: <p>When I try to get estimated file size using <code>AVAssetExportSession</code> instance <code>estimatedOutputFileLength</code> the app throws exception with reason <code>'Invalid presetName'</code>. Session initialized with <code>AVAssetExportPresetPassthrough</code> preset. Tested on iPod touch 4G with iOS 6.x</p>