SDHC Format Structure

This might seem a bit odd, but I'd like to know where to find out how my Canon SX10 IS formats an SDHC card. That is, the file structure on the card after it is formatted in the camera.

At a guess, it would have to create a structure / hierarchy of directories (folders) for the different things it can record - JPEGs at 3 compression levels, Video at 2 levels + the Stereo Audio (is that PCM?), then the Audio-only, which seems to be WAV.

I've Searched here on the Forum for a lead to the SDHC file structure, and also Googled, without any useful leads.

The reason is - I have 2 Cameras which use SDHC cards - the other is a Fuji S2000HD - kept for its 1280 x 720 MPEG4 *.mp4 extension, HD-Lo video. Both cameras have "their own" 2GB and 4GB SD and SDHC cards - that is, I keep them separated, in each camera's bag, when not in the camera.

I don't know if "mixing" them - reformatting them in different cameras - would cause problems, but at the silly prices SDHC cards are here - I don't want to find out!

The 4GB SDHCs from the Fuji open in a few seconds on all 3 PC system types here - XP-Pro SP3, Win2k SP4, and Linux.

The 4GB SDHCs from the SX10 are much slower to open in Windows and won't open at all in Linux. 4GB Flashdrives function normally in all 3 systems. A FAT32 External Hard Drive functions normally in all 3 systems.

So all are functioning as expected with USB2 devices - apart from the SDHC 4GB cards from the SX10.

A friend here suggested that there might be something "proprietary" in the Canon's file structure as formatted - needed to cope with Apple's Quicktime MOV container which the camera places on the H264 video files.

Which - apart from making the card-recorded files several times larger than the actual H264 video files are when the MOV container is removed on PC, seems to serve no useful purpose.

The older Fuji S2000HD, while its still images are "nearly" as good as a $100.00 P&S, is kept for its 1280 x 720 Standards Compliant MPEG4 / *.mp4 video. Which it does not put inside a MOV container - multiplying the file size several times over.

So we're wondering - is it the Canon's SDHC format file structure that's causing problems - or maybe "differences" needed for it to handle the H264 with the absurd bloating caused by the MOV containers.

At present with the SX10, I've bought it one more 2GB Class 6 card, and was planning to get another, "in place of" buying it another 4GB one, as there are no problems whatever with the 2GB cards - Class 6 or Class 4.

If there's no "fix" - as the Canon has only that one 4GB card, I'll see if the Fuji can format it and use it - and just use 2GB with the Canon.

Any leads or advice would be greatly appreciated, thanks.

Regards, Dave.

The storage media file system structures for all (current) Canon camera memory cards (and your Fuji cards as well) are FAT32. The specific directory structure is defined by the Digital Camera Image Management spec. as spelled out by JEITA in the Design Rule for Camera File systems. What you will find is that directories with large numbers of files will open slower in any system. It's possible that Fuji actually allocates a larger than "standard" block of space for a directory when it creates it on initialization; this has tradeoffs - you don't get a fragmented directory, so it can be read faster, but you'll waste space if you don't use all the directory entries. Canon doesn't do anything "odd" in its directory structures for the different file types; I routinely format my cards in my computer and pop them into whatever device (Netbook, e-book reader, camera, audio recorder) I may need them in.

One thing you may find speeds up the Canon - try creating new folders on a more regular basis. Don't let the system try to max out the folder before rolling over to a new one - 10,000 files is a lot of files to read the headers for. Even on my computer I break my directories up into 100-file chunks (300 files actually because each picture has a CR2, a JPG, and an XMP file).

If you read the Wikipedia articles on SD and SDHC you may learn something. As I recall the standards for these formats aren't well defined, and different manufacturers (of the cards this is, not the cameras) do things slightly differently.

I'd love to know why maybe 50% of the time, when I connect the 8gb CF card from my 5D to my laptop, via a portable USB2 reader, I get read errors and am told to scan the card for errors. None are ever found, and everything then proceeds normally. Never happens with the 32gb SDHC card I use in my G10.

I have another question, which I'll ask here in default of somewhere better. If instead of a CF card in my 5D I use an SD(HC) card in a CF adapter, will I notice any timing or other issues? Is it a sensible thing to do?