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Old Oct 3, 2005, 11:58 AM   #1
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Hi,
I just ordered a camera which supports video mode of 640x480 at 30fps.

This means effctive write speed required is

640x480 -> number of pixels in 1 frame
x 30 -> 30 frames
x 3 -> bytes per pixel (1 byte for each RGB)

is this calculation correct?

This comes out to be 27648000 bytes per second or 26-27MBps.
This seems incorrect to me..too large number i think

which all card support this speed?. i am looking for a 512MB or 1GB card
Thanks for ur time

Kuldeep
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Old Oct 3, 2005, 5:08 PM   #2
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No, that's not correct. The image data is going to be compressed, with file sizes being camera and video format dependent. You'll see a short sample movie in the image samples at the end ofeach camera's review here for many models.

Also, there won't be any current models that can actually write that fast to media, even if the data was not compressed. You have a bottleneck in the camera's interface to media with most models (even if you could find a card that fast).

What camera are you ordering it for?




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Old Oct 4, 2005, 2:12 AM   #3
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JimC wrote:
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>>>What camera are you ordering it for?
Quote:
JImc Thanks for replying. Ihave ordered the Nikoncoolpix 5900. In view of the compression that the camera usesi think 640x480size jpg photograph would be a good idea to redo calculations. I just saved one of my pics in 640x480 format. it comes out tobe around 200KB with best quality.So the required data rate is 200KB x 30 = 6000 KBps or 6Mbps. does that mean any card that supportsabove 6MBps will work for me. Iunderstand the size of JPGimage vary fromtype ofimage (guess it uses DCTtransform).So is this realist calculation again. Basically i am looking at the upper limiton Data transfer rate.



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Old Oct 4, 2005, 2:48 AM   #4
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Hi,

Picture and Movie compression works differently, Video compression also have different algotithm. For instance the MPEG compression, here is the way it compressed data in simple terms,

A reference frame is needed, the data for the next frame is the difference between the first and the second. It means that if there is no movement from the first frame to the next, there will be no difference or no data. The recording is grouped , I think for NTSC is about 15 frames.



For MPEG 1, it is roughly 10 megabyte per minute. An uncompressed AVI ( or MOV) will require 10 times more depending on the resolution.

DivX (variant of MPEG4) can record as low as0.5 megabyte per minute.

I have a Minolta Dimage Z3, for 320 x 240 at 30 fps, a 512MB card can hold only 16 minutes of MOV (quicktime) video at best quality, and only 8 minutes using 640 X 480 at 30fps also with best quality.








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Old Oct 4, 2005, 2:58 AM   #5
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Sorry. I should have made myself clearer. When I mentioned that you'd normally find a short movie in the image samples for camera's reviewed here, I assumed that you'd look at it to see how big the file was. But, I didn't expect you to try and use that for card requirements. I was only trying to point out that those kinds of transfer speeds are not necessary (the ones you were thinking it would need based on uncompressed images at 30 frames per second). ;-)

You can't go by whata camera uses for JPEG compression when shooting movies. The images in movie files are compressed much more than that.

It looks like this Nikon model takes just a little bit over 1MB of space per second for it's movies, since a 9 second movie in it's samples looks to be close to 10MB. You'll see a thumbnail to the .mov file in it's samples here:

http://www.steves-digicams.com/2005_...0_samples.html

But, you can't go by that buying cards either. Nikon probably has some better stats on how much space movies take in the user manual for it. That gives you an idea of transfer rates needed (but again, don't use that for buying cards).

You've got all sorts of processing bottlenecks to contend with in a camera, and some cards may work better than others due to compatibility issues, too.

Most non-DSLR cameras are not going to write at anywhere near most rated card speeds (due to the interface to media being slower than the cards). But, you can still see differences between card brands.

I'd probably get a cards like the Sandisk Ultra II for it (even though a slower card may work fine).

I did some digging around and it looks like that card is a favorite in it (as it is for many other camera models). It's reasonably priced now that the faster Extreme III is shipping, too (and you don't need a card that fast).


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Old Oct 5, 2005, 2:17 AM   #6
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Thanks JimC..That was helpful. I finally purchased a Kingston 1 GB Elite pro card...



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Old Oct 5, 2005, 9:49 AM   #7
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kkdeep wrote:
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Thanks JimC..That was helpful. I finally purchased a Kingston 1 GB Elite pro card...

That would have been the very last card I chose (it had some compability problems with some Canon and Konica-Minolta models, depending on the "generation" of the card and the firmware version of the cameras, making them very slow.

For example, a number of Canon S2 IS owners reported that some of these cards were useless for video prior toCanon's new firmware for this camera.

But, I don't recall seeing any similar compatibility issues reported by Nikon owners, and they seem to work fine in most camera models, even with older generation cards.

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Old Oct 7, 2005, 6:26 AM   #8
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JimC wrote:
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kkdeep wrote:
Quote:
Thanks JimC..That was helpful. I finally purchased a Kingston 1 GB Elite pro card...
style="BACKGROUND-COLOR: #666666"
Quote:
That would have been the very last card I chose (it had some compability problems with some Canon and Konica-Minolta models, depending on the "generation" of the card and the firmware version of the cameras, making them very slow.

Oops!!

Well i already made the choice. Let me seen if i can find some issue. i


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Old Oct 7, 2005, 7:56 AM   #9
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AFAIK, it should work fine in your Nikon. The compability issue in the Canon models like the S2 ISwere fixed by a firmware update (so it may have been Canon's problem anyway). As for the KM models, they tend to be a bit more "finnicky" on what cards work best.


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Old Oct 9, 2005, 4:06 AM   #10
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I've just bought one of these Multimedia plus cards which in effect is a SD card without the write protector, popped it into my Canon A620 and tried the 640x480 movie mode, works perfectly

http://www.flash-memory.co.uk/pp/Multimedia_Cards_(MMC)/Kingston_1GB_48x_Multimedia_Card_-_MMCPlus.html
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