FH1 and SDHC

[ad78]

hi there newbie here.

2 days ago i ordered FH1 on amazon. oh well, shipping says it should be here on friday, july 3. the right time to take sample on holiday!

now i saw this very good deal on samsclub and they have toshiba 16gb sdhc class 4 for $29 pick this afternoon at my local samsclub.

my question now is. how is class 4 when recording @ 1080p 60p? is there any lag or issues? let me know if none so i can buy 1 more 16gb at sams
or if there is any issues i will buy 32gb class 6 over ebay.

thanks in advanced!

[subc]

Well, 1080P at 60 frames per second... according to Sanyo specs, the maximum bitrate is 24Mbps (megabits per second). That translates to 3072 kilobytes per second, and that translates to exactly 3 Megabytes per second.

According to Toshiba's website, the maximum read/write speed for their SDHC class4 cards is 6 megabytes per second, which is twice the bandwidth that the FH1 requires on the 1080P @ 60fps setting.

You got to remember that the 6 megabytes per second is a maximum, and will probably not be constant, but the card does meet the specifications of Class 4 standard, a speed standard that requires a data write speed of at least (as in, a minumum of) 4MB. So you still would have an extra megabyte of 'bandwidth' as a buffer.

[ad78]

thanks man. well said

i am like a madman tracking my FH1

[ronaldkwok]

I have been using class 4 SDHC cards (Kingston, 8GB) in my HD2000 (similar to FH1) and did not notice any problem. So coupled with the theory in the post from subc, I suppose class 4 SDHC cards are OK for the FH1. Happy holiday videoing!

[ad78]

Originally Posted by ronaldkwok

I have been using class 4 SDHC cards (Kingston, 8GB) in my HD2000 (similar to FH1) and did not notice any problem. So coupled with the theory in the post from subc, I suppose class 4 SDHC cards are OK for the FH1. Happy holiday videoing!

are you in maximum settings? in that case i will buy one more 16gb at sams
thank you

[subc]

I do not foresee any problems using the maximum quality settings of the VPC-FH1 with a class 4 card. Another thing to remember is that the camera interfaces directly with the connectors of the memory card, thus reducing any potential loss of data transfer speed (as opposed as using the SDHC cards on the computer with a USB adapter).

[ronaldkwok]

Originally Posted by ad78

are you in maximum settings? in that case i will buy one more 16gb at sams
thank you

Yes, sir!

[ad78]

Originally Posted by ronaldkwok

Yes, sir!

cool man.

thanks gents

[hsbsitez]

for a 10 min video, I experienced about 1-2 min waiting time after I stopped the recording. It took sometime for it to write file to my card, for some reason.

[whitis]

Originally Posted by subc

According to Toshiba's website, the maximum read/write speed for their SDHC class4 cards is 6 megabytes per second, which is twice the bandwidth that the FH1 requires on the 1080P @ 60fps setting.

Good analysis, but incomplete. Latency may also be lower on the class 6 card and the difference between average performance and worst case performance may be tighter. In addition to writing the image data, the camera also has to update the file system, in particular FAT sectors, and directory entries. So, every so often, instead of writing one sector to write one sector of information, it may have to write up to 3 and read 1. And occasionally, it needs to close a file and open a new one. On real time systems with limited memory, this can be a big deal. Particularly, if the code is simpler than it really needs to be. Now, on a video camcorder, this should be less of an issue because you have to queue up your writes anyway. But we already know (poor handling of 4GB limit) that the FAT handling code is simpler than it really needs to be. And it could be that the camera basically writes the last frame out while acquiring the new one, sharing the last frame buffer also needed by the encoder (well, actually, expecting to dispose of the data as soon as it comes out of the data with limited buffering), which could mean that if one frame takes a little to long to write, the camera can't proceed to the next one without losing some of the previous one. This is an example of how the system can be latency sensitive, even if the bandwidth is there. And the bandwidth to write 3MB/sec video data is actually a little bit higher than the 3MB/sec because of file system overhead. Not much greater on a freshly formatted card but when things get fragmented the overhead can be substantial. When fragmented, the camera may need to read multiple FAT sectors to find a free sector. In pathological cases, it may spend as much or more time searching the FAT than writing the data. SDHC (and other flash cards) do things like wear leveling and bad sector elimination which means that more data is being moved around internally and timing is not a simple as one might think. Worst case includes a fragmented card that is almost full.

In theory, the speed ratings on the cards are minimums (but over what time period). Cards may not actually meet the specs they claim to meet over all conditions, they are not necessarily tested for compliance by a third party. One would hope that a class 6 card would have a better chance of always meeting class 4 specs.

So, while it appears that Class 4 gives a significant safety margin, one must recognize that a substantial safety margin may actually be needed.
A class 4 card will probably work most of the time, but most of the time isn't always good enough. If you are using a class 4 card, be more careful about erasing all the files, or better yet periodically reformatting the card, to keep the overhead down and avoid filling up the card completely.

And if you are testing to see if a Class 4 card works, don't do it on a freshly formatted card that is almost empty. Record a bunch of alternating long and short clips, filling up the card, then delete a few of the short ones to create something that is, while not worst case, at least somewhat of an approximation of worst case.

Class 6 cards could have a significant (roughly 50%) speed advantage when it comes time to transfer the data that has already been recorded. When you go to dump 1.5 hours of video to the PC or a hard drive, a class 6 card should be able to do it in about 45minutes vs 69 minutes for the Class 4. If you are out of cards and need to shoot some more, or need to start editing/viewing after a long shoot, that is a significant difference. That alone could be worth the slightly higher prices. Not having corrupted footage which is difficult, expensive, and/or impossible to reshoot could definitely be worth the price.

Thus, I would say you probably can use class 4 but should use class 6, especially for anything critical. If you have a mix of class 4 and class 6 cards, use the class 6 for the important stuff.

From looking at the manuals, it looks like the camera is capable of copying files from SDHC to a locally attached hard drive without a computer, but as far as I can tell from the documentation, it isn't capable of recording video directly to the hard drive, which would be helpful in various situations where you are shooting a lot of video, or copying files in the background while also shooting (use a hard drive enclosure with built in SDHC slot and copy function for this).