iPhone 4 Video very quiet is there something wrong?

Make sure you're not covering up the microphone while recording. If you look at the bottom of the phone, the two things that look like speakers. The right one is the speaker, the left is the microphone.

I would guess you are covering it when recording video, or pointing it in such a way it is away from the audio source.

Okay. Just figured I would point out the easy solution first, just in case.

Similar problem here. I think it's due to the noise canceling mic on the top of the phone, and the way you hold it. When you're holding it, you normally have your hands at either end of the phone, essentially cupping all sound into both mics. The phone thinks that all that sound is background noise (because it's going into both mics) and removes it. Quite annoying.

Edit: Just took some test videos and noticed something odd. Covering up the top (noise canceling) mic results in quiet and noisy audio, but covering up the bottom mic results in no change in audio. It appears the phone uses the top mic to record audio during video capture. I think this may be because Apple assumed people's hands would be covering the bottom mic when they were starting/stopping the video.

I am having the same issue, I have determined that when recoding video the iphone 4 records from both the bottom mic and the top (noise cancelling mic). I have tested this on another iPhone4.

My phone only records from the noise cancelling mic, giving it a hollow faint sound when played back.

This effects FaceTime as well.

The bottom mic doesnt work for face time or video recording, but it does work for phone calls and voice memos.. very odd

paying a visit to the apple store tomorrow

Apple replaced defective phone, first case he had seen