Video
Here is the same formula as last year for calculating the size in kilobytes (KB) of one frame of uncompressed video:
Code:
Frame size K = ( [Pixel Width x Pixel Height x Bit Depth] / 8 ) / 1024
Where 8 represents an 8-bit byte, and 1024 equals the number of bytes per kilobytes.
To determine the file size of one second of uncompressed video, multiply the image size by the number of frames per second (fps).
To determine how compression affects file size, divide the file size by the compression ratio.
Last year I used a final estimate of 60:1 compression ratio. This turned out to be very close to actual video. My estimate for iPhone 4 720p HD video was 79MB a minute and real videos came out to about 83MB. About 1 MB of this difference could be the audio recording, so only about 3 MB off. This little amount could easily vary depending on what you are recording and how well the compression can work. So Im going to go with the same 60:1 compression ratio for calculations this year.
Code:
iPhone 4S video size per 1 min of video at 1080p (1920 x 1080):
( [1920 x 1080 x 24] / 8 ) / 1024 = 6075 KB / frame
6075 KB/frame x 30 frames/sec = 182250 KB/sec
182250 KB/sec / 60 compression ratio = 3037.5 KB/s compressed
3037.5 KB/sec compressed * 60 s / min * 1 MB / 1024 KB = 177.98 MB / min
Comparing the iPhone 4S 178 MB / min number to the iPhone 4 calculated number of 79MB / min, the iPhone 4S 1080p video takes up about 2.5 times as much space as the iPhone 4. So using a more moderate estimate of keeping 60 minutes of video on your camera roll you are looking at 10.4 GB of storage vs 4.6 GB for the iPhone 4, so that can add up quick.