Hi Guys,
in image processing applications what is considered real time? Is 33 fps real time? Is 20 fps real time? If 33 and 20 fps are considered real time then is 1 or 2 fps also real time?
Can anyone throw some light.
Vikram
+3
A:
In my experience, it's a pretty vague term. Often, what is meant is that the algorithm will run at the rate of the source (e.g. a camera) supplying the images; however, I would prefer to state this explicitly ("the algorithm can process images at the frame rate of the camera").
Martin B
2010-10-18 08:01:32
A:
That's not actually an easy question (even without taking into account differences between individulas).
Wikipedia has a good article explaining why. For what it's worth, I think cinema films run at 24fps so, if you're happy with that, that's what I'd consider realtime.
paxdiablo
2010-10-18 08:01:38
A:
i think it depends on what the real time application is. If the app is showing slideshows with 1 picture every 3 seconds, and the app can process 1 picture within this 3 seconds and show it, then it is real time processing.
If the movie is 29.97 frames per second, and the app can process all 29.97 frames within the second, then it is also real time.
An example is, if an app can take the movie from a VCR or Cable's analog output, and compress it into 29.97 frames per second video and also send all that info to a remote area for another person to watch, then it is real time processing.
動靜能量
2010-10-18 08:01:42
+1
A:
The notion of real-time display is not really tied to a specific frame rate - it could be defined as the minimum frame rate at which movement is perceived as being continuous. So for slow moving objects in a visual frame (e.g. ships in a harbour, or stars in the night sky) a relatively slow frame rate might suffice, whereas for rapid movement (e.g. a racing car simulator) a much higher frame rate would be needed.
There is also a secondary consideration of latency. A real-time display must have sufficiently low latency in relation to other events (e.g. behaviour of a real-time simulation) that there is no perceptible lag in display updates.
Paul R
2010-10-18 08:02:09
A:
It depends on what exactly you are trying to do. For some purposes 1fps or even 2 spf (Seconds per frame) could be considered real-time. For others thats way too slow ...
That said, real-time means that it takes as long (or less) to process x frames as it would take to just present those x frames.
Goz
2010-10-18 08:02:16
+2
A:
Strictly speaking, I would say real-time means that the application is generating images based on user input as it occurs, e.g. a mouse movement which changes the facing of an avatar.
How successful it is at this task - 1 fps, 10 fps, 100 fps, etc - is actually another question.
Real-time describes an approach, not a performance metric.
If however you ask what is the slowest fps which passes as usable by a human, the answer is about 15, I think.
Blank Xavier
2010-10-18 08:02:21
A:
It depends.
automatic aircraft cannon - 1000 fps
monitoring - 10 - 15 fps
authentication - 1 fps
medical devices - 1 fph
iddqd
2010-10-18 08:07:35
+1
A:
(Hard) Real time is when an outcome has no value when delivered too early or too late.
Any FPS is real time provided that displayed frames represent what should be displayed at the very instant they are displayed.
mouviciel
2010-10-18 08:14:39
A:
I guess the term is used with different meanings in different contexts. In industrial image processing, real time processing is usually the opposite of offline processing. In offline processing applications, you record images (many of them) and process them at a later time. In real time processing, the system that acquires the images also processes them, at the same time, so the processing frame rate must not be higher than the acquisition frame rate.
nikie
2010-10-18 08:23:26
+1
A:
Real time image processing = produce output simultaneously with the input.
The input may be 25 fps but you may choose to process 1 of every 5 frames(that makes 5 fps processing) and your application is still real time.
TV streaming software: all the frames are processed.
Security application and the input is CCTV security cams: you may choose to skip some frames to fit the performance.
3d game or simulation: fps changes depending on the current scene.
And they are all real time.
honibis
2010-10-18 08:47:18
A:
Real-time means your implementation is fast enough to meet some deadline. The deadline is part of your system's specification. If it's an interactive UI and the users are not too picky, 15Hz update can be OK, although it can feel laggy. If you're using it to drive a car along the motorway 30Hz is about right. If it's a missile, well, maybe 100Hz?
Martin Thompson
2010-10-18 20:24:12