According to the rules of the English language, if the first syllable of the word shock and have the letter "i", this sound is pronounced as [ai]. However, as we know, almost all grammar rules have exceptions. For example, a well-known company for the production of Nikon cameras. In this case, the first letter "i" is read as short sound [i].
However, the official representatives of the company, making presentations, called his product "Viber", which is why this form of pronunciation can be considered correct. However, even many native speakers use the word "viber". You need to understand that in the English language (as in Russian, and many others), have their own dialects. They largely determine the pronunciation of words. So in many southern us States a rule for replacing the sound [i] in [ai] simply not working.
So how to pronounce the word Viber, everyone decides for himself. The singular error in this case is not, as many borrowed words rusifitsiruetsya with wrong pronunciation or accent. For example, the word laboratory in English sounds like a laboratory and the stress falls on the second syllable, whereas in Russian on the fourth.