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Old August 31st, 2009, 03:38 PM   #1
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How to calculate memory...

A) I just got a cam that will shoot 720 at 60fps .. The battery is purported to last 80min at continuous running. How would I calculate the SD memory req'd to not run out of memory before the 80min was over?

B Is there marked difference between SD and SDHC.

Thanks for the help...

Jim
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Old September 7th, 2009, 10:14 AM   #2
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You need to know the bit rate in kbps (kilo bits per second) or mbps (mega bits per second to do the calculation. Memory is measured in bytes, which are each 8 bits. So 80 minutes x 60 seconds per minute x bit rate / 8 / 1.073* / 1,000,000,000 = Gigabytes of memory.

Remember to convert kilo or mega to actual bits for the calculation. 1 kilo bit = 1000 bits, 1 mega bit = 1,000,000 bits.

*the 1.073 is because a Gigabyte is conventionally 1,073,000,000 bytes due to binary math (2^30).
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Old September 8th, 2009, 06:53 AM   #3
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Oh God ..David. My brain is starting to hurt. I was a summer school student, not grad school. Give me a big ball of string; I'd have to simply unroll it and measure it inch-by-inch.

I'll report back: I'll top the battery and fill the 4MB SD card. Thanks.

Jim
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Old September 8th, 2009, 11:53 PM   #4
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There is a difference

Hey Jim, There is a difference between SD and SDHC cards. In simple terms SDHC cards start writing data a specified speed and sustain that speed, whereas regular SD Cards start writing data at 0MB/Sec and build up to a top speed; SDHC memory cards start writing the data at a higher minimum speed.
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