Posted by
Charles M. Shaw on
Jun 24, 2008; 12:00pm
URL: http://imagej.273.s1.nabble.com/Flow-tracking-tp3695757p3695760.html
Frame rate is stored in the AVI RIFF main header in the field
dwMicroSecPerFrame, so I doubt its a limitation of the file format.
Redrawing 300 images per second can be a pretty significant load on the
system, though, not to mention beyond the refresh rate of most monitors
by about 5x.
If the motion you've captured is as slow as you describe, perhaps you
could save something like every 5th or 10th frame of your original
movie and output an AVI at either 60 or 30 fps? If you've been viewing
the videos in ImageJ at "300 fps," you've probably been doing
essentially that since your monitor most likely works in the 60 Hz
range (not to mention the limitations of the human eye).
Charlie Shaw
Graduate Student
Macromolecular Science & Engineering Program
University of Michigan, Ann Arbor
On Jun 23, 2008, at 2:57 PM, John Oreopoulos wrote:
> My mistake, I should have written "fps" for the playback frame rate
> instead of "ms". I got my units mixed up. The sentences should read:
>
> To see the protein dynamics, it is necessary to play back the image
> sequence with a 300 fps frame rate on the computer screen in ImageJ,
> which is possible with the latest version of ImageJ (max frame rate
> 1000 fps or frame rate allowed by memory and processor speed).
>
> I usually save image sequences as .avi files, but I've noticed that if
> I do this when the display frame rate in ImageJ is greater than 100
> fps, the avi is saved with a frame rate of 100 fps.
>
> John
>
> On 23-Jun-08, at 2:27 PM, John Oreopoulos wrote:
>
>> Dear ImageJ listserver,
>>
>> I have a small problem I was hoping the community might be able to
>> advise me on. I have several long time-lapse live-cell image
>> sequences captured using TIRF microscopy. 1000 images were captured
>> with a 200 ms exposure time and a 500 ms delay in between exposures.
>> A typical image sequence file size is about 500 MB. It is necessary
>> to capture many images and with this rate of repetition since the the
>> cells I am imaging express a fluorescent membrane protein that
>> exhibits very interesting dynamics (both fast and slow motions) and
>> over a long time period. I do not have the option of capturing fewer
>> images over the same time interval since doing so will cause the
>> software to miss recording very transient and fast vesicle fusion
>> events with the membrane. We use ImageJ for analysis and we run the
>> program on a powerful Linux computer with 4GB of RAM. To see the
>> protein dynamics, it is necessary to play back the image sequence
>> with a 300 ms frame rate on the computer screen in ImageJ, which is
>> possible with the latest version of ImageJ (max frame rate 1000 fps
>> or frame rate allowed by memory and processor speed). If played
>> slower than this, then it's difficult for the human eye to discern a
>> fusion event and notice any protein motion.
>> My problem is that I would like to make these movies portable for
>> presentations (in Powerpoint or Quicktime for example) without too
>> much compression that masks the features I'm trying to show and
>> without slowing them down to a lower frame rate.
>> I usually save image sequences as .avi files, but I've noticed that
>> if I do this when the display frame rate in ImageJ is greater than
>> 100 ms, the avi is saved with a frame rate of 100 ms. Is this a bug
>> or is it simply a limitation of the .avi format, or is it a
>> limitation of the player I use to playback the .avi file (Quicktime)?
>> I can find no mention of a maximum frame rate in the .avi writer
>> plugin on the ImageJ website.
>> Even if I can save files properly with these high frame rates, I
>> likely will not be able to embed them in Powerpoint and play them at
>> that speed since the demands on my laptop for this file size and
>> display rate are too great. Does anyone know of an alternative way
>> for displaying large movies with high frame rates?
>>
>> Thank you for your time.
>>
>>
>> John Oreopoulos, BSc,
>> PhD Candidate
>> University of Toronto
>> Institute For Biomaterials and Biomedical Engineering
>> Centre For Studies in Molecular Imaging
>>
>> Tel: W:416-946-5022
>