Performance Considerations

Copied from Instascan by Chris Schmich:

Many factors affect how quickly and reliably ZXing can detect QR codes.

If you control creation of the QR code, consider the following:

• A larger physical code is better. A 2" square code is better than a 1" square code.
• Flat, smooth, matte surfaces are better than curved, rough, glossy surfaces.
• Include a sufficient quiet zone, the white border surrounding QR code. The quiet zone should be at least four times the width of an individual element in your QR code.
• A simpler code is better. You can use this QR code generator to see how your input affects complexity.
• For the same length, numeric content is simpler than ASCII content, which is simpler than Unicode content.
• Shorter content is simpler. If you're encoding a URL, consider using a shortener such as bit.ly.

When scanning, consider the following:

• QR code orientation doesn't matter.
• Higher resolution video is better but is more CPU intensive.
• Direct, orthogonal scanning is better than scanning at an angle.
• Blurry video greatly reduces scanner performance.
• Auto-focus can cause lags in detection as the camera adjusts focus. Consider disabling it or using a fixed-focus camera with the subject positioned at the focal point.
• Exposure adjustment on cameras can cause lags in detection. Consider disabling it or having a fixed white backdrop.