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Old 04-16-2012, 07:32 AM   #36
Chas Tennis
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Join Date: Feb 2011
Location: Baltimore, MD
Posts: 2,992
Default High Speed Video and Cheap, Slow SD Cards - CORRECTION 9/21/2012

CORRECTION 9/21/2012 - I just recorded some 120 fps & 240 fps videos and after recording normally for many seconds a 2Gb cheaper card seems to skip frames.

I have read several discussions of the speed requirements for SD cards. To be safe I'd always get exactly what the camera manufacturer recommends.

I am not that knowledgeable in digital technology but found something interesting for my high speed videos. It involves using cheap, slow 2GB SD cards to take and communicate high speed videos. Maybe these slow cards are OK for high speed video of short video clips.

If you want to communicate videos at low very cost and simply, for example, of many tennis strokes, I have found the following methods with limitations:

1) Attach to emails - my internet provider limits the attachments to total about 15 MB per email. It can be cumbersome to find each file and attach them as when I sent a team of tennis players their strokes.

2) Upload to video host site such as Youtube or Vimeo. However, these sites compress the video files farther for storage and the compression, I believe, interferes with proper stop action frame-by-frame analysis. On site, the best you can do is to press the play-pause button as fast as possible. Free Vimeo has a 500MB limit per week. Vimeo also has a $10?/month 'Pro' service that saves uncompressed files that can be downloaded and viewed in proper stop action.

3) Upload file to a drop box (any file type). I had used a site for up to 100MB original video file with no compression. You then send email to player who can download the complete file. Not sure of the status of the service now.

4) Cheap SD Cards. As another method of communicating videos, especially longer ones, I considered buying cheap SD cards as loaners. 2GB card cost about $5 with another $5 for shipping, maybe cheaper if you look. These cards are slow or unspecified. Also bought a cheap card reader as a loaner in necessary.

5) Others Methods? Any other suggestions for communicating at low cost and not requiring computer knowledge or computer set-up changes from those receiving the video files?

I tried my Class 2? and 4 cheaper 2 & 4 GB cards for recording high speed video of tennis strokes in a Casio FH100 camera. 240fps requires 50Mb/sec. Despite the slow card speed they have worked perfectly so far. According to most forum discussions on SD card speed requirements, the cards should probably have dropped frames so my recordings did not make sense. See CORRECTION above.

I started a thread on dpreview and got a very interesting reply that makes sense. It says that for short video clips there is a buffer in the camera that can relax the speed requirement from the card.

See especially 3rd reply.

http://forums.dpreview.com/forums/re...ssage=41196068

If true the video clip length is important and might vary considerably because of the buffer size in different cameras.

It was also pointed out in the dpreview thread that large, fast SD, 32GB, are now very reasonable in cost. Selected files could then be copied to the small SD cards for individual players. Copying requires an additional step and computer whereas the cheap SD card could just be handed to the player after the practice secession.

Any guinea pigs for some tennis stroke videos around Baltimore?

Last edited by Chas Tennis : 09-21-2012 at 04:31 AM. Reason: correct status of file drop box method.
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