i need to compare differences between the consequent frames?

HI everyone

i have a project to complete! i took a video then partition it to frames . i need to compare differences between the frames. The proces should be as follow: 1. We shall start with the first frame of the video, it is the reference frame. 2. Compare the second frame with the first frame. 3. Compare consequent frames to find which frame has got a big differences with reference frame. 4. Now we take the new frame that shows difference with the first frame(reference frame). 5. Repeat the above mention process to find new reference frames.

6. Keep all the 'selected' frames.

i need to new algorithm or what to do that? and if you can help me .

[hsein Msw]

oun aloun hello,

did you finish your project ?i have the same one ...can you give me the code?

[john miller]

I want to segment the same object in selected frames and compare its size to the size in the reference frame. The objective is to use change in size to estimate distance from the object when it was captured in the refernce frame.

Answer 1

[Walter Roberson]

No, that is an algorithm. However, you need to figure out what you mean by "big" for "which frame has got a big differences".

[oun aloun]

thank you very much to replay Walter Roberson i mean how i can Appointed the threshold between the first frame with a new frames .and etc

[Walter Roberson]

First you need to define what a "difference" is and how you would measure how much difference there is.

For example, if there is no motion between frames but a light gets turned on, changing the brightness of most of the pixels, is that a big difference? If the light stays mostly the same but an object that occupies about 1/16th of the image moves 5 pixels to the right, is that a big difference?

I get the impression that you are trying to determine "key frames" for video compression purposes. One thing that you need to understand about "key frames" is that they depend in part upon what kind of changes you can efficiently represent. A change could look important to humans but if only took a small amount of information to represent the change then for video compression purposes it would not be a big change that was worth creating a new key frame for. Likewise a change might not look like much to humans but it might happen to take a lot of information to represent the change and it might be worth creating a new key frame.

When you are encoding changes compared to the frame before, you need some overhead information about what kind of change it is, the area it is affecting, and what the new values are. When there is a sufficiently large change compared to the frame before, sometimes that overhead can add up to enough that it takes less information to say "Forget all that, it has gotten too complicated, start over with the following full frame". And those places, where the encoding of all the changes would take more space than just outputting a full frame, those are the "key frames".

There are a couple of other times that "key frames" might be used:

• sometimes you are following a video standard that sets a maximum limit on the number of frames you can go before a key frame, so you just create one because you are expected to
• reconstructing a frame from a list of changes takes computation time and memory, and sometimes there just is not enough compute power available to decode the changes in time, causing the video player to glitch. Once the playback has glitched it cannot recover until it encounters a key frame, so you make it a practice to output key frames from time to time to limit the amount of time the player will stay in the glitched state. This is part of the reason that standards state limits on the number of frames between key frames
• you might be working with an unreliable stream that loses updates sometimes, such as UDP. If you are always building off of the previous frame then the lose of a frame causes a glitch in the playback that cannot be recovered until a key frame is received; this is another reason that standards make limits on the number of frames
• the more frames between key frames, the more memory it requires to play frames backwards, because the process needs to search for the previous key frame and construct the list of changes from it and remember that frame, and construct the changes after that and remember that frame too and so on so that it can create a smooth playback going backwards

[oun aloun]

Walter Roberson

thank you

this a group of my frames in attachment file(frames.zib)

i need anyway to appoint the frame which have a new object not appeared in previous frame this frames taken from underwater when you look to frames you can see small Different in pixel and small Different in histogram but in on frame you will found a new object not appeared in the first frame .

that what i want.

thank you very much

[oun aloun]

frames

[Walter Roberson]

Those are really bad resolution. 480 x 320 only, and blurry.

Those are JPEG images. Never use JPEG images for scientific analysis if you can avoid it.

Some of the frames are identical to the previous frames.

Other than those identical frames, it appears to me that every frame introduces a new object.

[oun aloun]

this my problem

but i will try to get a good resolution and i will convert the (Jpg) to another type

but i need good idea to solve this problem (identifies the new object in frames, and select a frame which have different from first frame and go on to last frame. )

thank you very much I am grateful with your responses(Walter Roberson)

[Walter Roberson]

Is the question now reduced to identifying frames that are identical to the previous ones? Because other than those ones, every frame introduces a new object it appears to me. If that is not what you observe then it could be that your definition of "object" is different than my definition of "object". Some of the objects I see are pretty small. I speculate that when you talk about "object" you might be referring to the coral. If your task is detecting the coral then you should say so, as then we would have particular characteristics to focus on, instead of "I know it when I see it" that might otherwise be used.

Answer 2

[hsein Msw]

i have the same project ... did you got the code?