How to calculate memory... at DVinfo.net

Jim Cancil · August 31st, 2009, 02:38 PM

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

David Ennis · September 7th, 2009, 09:14 AM

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).

Jim Cancil · September 8th, 2009, 05:53 AM

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

Calvin Bellows · September 8th, 2009, 10:53 PM

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.

August 31st, 2009, 02:38 PM	#1
Jim Cancil Regular Crew Join Date: Mar 2008 Location: Salisbury Maryland Posts: 161	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

September 7th, 2009, 09:14 AM	#2
David Ennis Fred Retread Join Date: Jul 2004 Location: Hartford, CT Posts: 1,227	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). __________________ "Nothing in the world can take the place of persistence..." - Calvin Coolidge "My brain is wired to want to know how other things are wired." - Me

September 8th, 2009, 10:53 PM	#4
Calvin Bellows Major Player Join Date: Feb 2009 Location: Red Deer, Alberta Posts: 215	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. __________________ Calvin Bellows www.exposureproductions.ca

September 8th, 2009, 05:53 AM	#3
Jim Cancil Regular Crew Join Date: Mar 2008 Location: Salisbury Maryland Posts: 161	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