SOT: Calculating video size per hour at 24mbps

VMP wrote on 4/3/2011, 8:01 AM

Hi,

If a camera uses 24mbps how much GB in size would the file be at 1 hour?

I think I am doing something wrong when calculating.

1 sec = 24mb (x 60 seconds = 1440 MB/per minute)

1 minute = 1440 MB (x 60 minutes = 86400 MB/per hour)

1 hour = 86400 MB / 86,64 Gig for 1 hour video?? that doesn’t seem right.

I am trying to buy a memory stick for my DSC-HX100V camera as mentioned in my previous post.

On the net it is written that HD uses about 11 Gig/hour.
So I think that a 16 gig memory stick as the MSHX16A will be enough, but I don’t understand how the calculation works.

Thanks for any reply,
VMP

Comments

musicvid10 wrote on 4/3/2011, 8:48 AM

Mb = Megabit
MB = Megabyte

No camera you'll ever use shoots 24 MB per second, unless you're loaded with cash.

The correct calculation is:
24 x 3600 = 86400 Mb/hr x .00012 = 10.55 GB/hr
so 11 GB/hr is about correct for 24 Mbs video with audio, depending on how it's recorded..

VMP wrote on 4/3/2011, 9:25 AM

Thanks musicvid,

So its '.00012' bit instead of 'byte' that I got confused with I guess :-).

VMP

musicvid10 wrote on 4/3/2011, 9:29 AM

One Megabit equals approximately .00012 Gigabytes.

arenel wrote on 4/3/2011, 9:53 AM

24Mbs = 8MBs x 3600s/hr = 10.8GB/Hr
Ralph
Have I got it?

musicvid10 wrote on 4/3/2011, 10:17 AM

1 MB = 8 Mb, so:

24 Mbs = 3 MBs x 3600 = 10.8 GB/hr
Then you've got it!

VMP wrote on 4/3/2011, 10:36 AM

MSHX16A memory size: 16GB
Usable capacity (approx.) : 14.9GB

So let me see how much video will fit into this memory stick ;-).

24Mbps x 60s X 0.00012 = 0,1728 GB = 172,8 MB per minute.

Memory stick: 14.9GB (14900 MB)

14900 MB (capacity)/ 172,8 MB (minute unit) = 86,22 minutes

----
Or
----

3MBs x 60s = 180 MB per minute.

14900 MB (capacity)/ 180 MB (minute unit) = 82,77 minutes

VMP

musicvid10 wrote on 4/3/2011, 10:45 AM

If you are talking about video only, the second estimate is more correct due to my rounding error in the first calculation -- should actually be .000125

But remember, you need to add in your audio too, and that is figured in exactly the same way once you know your audio bitrate.

Either way, an hour should be safe on a 16 GB stick.

VMP wrote on 4/3/2011, 11:10 AM

Ah yes :-) thats' true, thanks.

'Audio Format : Dolby Digital (AC-3) / MPEG-4 AAC-LC'

No bitrate info on the HX100V info site.

Maybe it can be set manually to for example 320 kbps.

320 kbps = 0.0390625 megabyte x 60 = 2,34 MB per minute.

2,34 MB per minute.x 60 = 140 MB per hour.

---------------------

Video+ Audio MB size per hour:

140 MB per hour (audio @320kbps) + 10368 MB (video @24Mbps) = 10508 MB = 10.508 GB

VMP

amendegw wrote on 4/3/2011, 1:11 PM

"the second estimate is more correct due to my rounding error in the first calculation -- should actually be .000125"Actually, the first calculation may be the more accurate - depending upon what the manufacturer means by 16GB - is that GigaByte or GibiByte? e.g. 10.8 * 1000 / 1024 = 10.55

See: http://en.wikipedia.org/wiki/Gigabyte "When referring to RAM sizes it most often (see binary prefix adoption) has a binary interpretation of 1024x1024x1024 bytes, i.e. as an alias for gibibyte. File systems and software often list file sizes or free space in some mixture of SI units and binary units; they sometimes use SI prefixes to refer to binary interpretation – that is using a label of gigabyte or GB for a number computed in terms of gibibytes (GiB), continuing the confusion."

Oh, and by the way, how many angels do, indeed, dance on the head of a pin? [grin]

...Jerry