tiff writing

[Kryer]

Hi,
my problem is the following:

I'm are currently using Labview 5.1 and IMAQ visions 4.1 (I know its old but worked fine till now :o)).
I need to acquire and save at a speed of about 3-5 pictures per second and save the files during almost 15 mins.
My problem is that the "Write Tiff file" in IMAQ is too slow, it needs about 150 ms per acquisition and this way it needs almost more time to write to disk than to acquire our data.

Is there a faster .VI somewhere around or how do I write to a buffer big enough to handle all the data while I'm still acquiring ?
Does anyone know, why the .vi takes "that" (sure its still quick ;o))long? What parameters does it depend on ?

Thanks

[chilly_charly]

As far as I know, TIF is a variety of bitmap, with no data compression. Therefore, the time taken to write to a file should depend mainly on the image size. Haev you tried some benchmark timings to compare a raw byte writing to the TIF writing ? What is your image size (HxL, bit depth) ?

[Kryer]

our image size is about 256x256 in 8bit (we may go to 16bit later on).

As our program takes about 150ms per frame longer when the save to disk feature is activated, we assumed this waws the time taken by the .vi.
Without that .vi everything works out fine.

[DFGray]

TIFF (Tag Image File Format) is one of the oldest and most feature-rich bitmap formats around. It is still the format of choice for graphic artists. It has a plethora of options, many of which can slow you down. It is not well supported by inexpensive software due to its complexity. That said, you can get lots of info about it on the web. Here is a portal that may point you in the right direction:

http://www.faqs.org/faqs/graphics/fileformats-faq/part3/section-147.html

You disk write speed is something under 500k/sec, so something is obviously wrong. It may be that the IMAQ routine takes awhile to format the image into a TIFF file. Try a different format (e.g. GIF or PNG). Don't use compression - it will slow you down. This holds true for TIFF, GIF, and PNG, all of which support compression (last I checked, TIFF supported six or more compression modes).

Good luck!