Grabbing consecutive frames in android using opencv

Question

I am trying to grab consecutive frames from android using opencv VideoCapture class. Actually I want to implement optical flow on android for which i need 2 frames. I implemented optical flow in C first where I grabbed the frames using using cvQueryFrame and every thing work fine. But in android when I call

 if(capture.grab())
  {
     if(capture.retrieve(mRgba))

        Log.i(TAG, "first frame retrived");

  }
  if(capture.grab())
  {
    if(capture.retrieve(mRgba2))

    Log.i(TAG, "2nd frame retrived");
  }

and then subtract the matrices using Imgproc.subtract(mRgba,mRgba2,output) and then display the output it give me black image indicating that mRgba and mRgba2 are image frames with same data. Can any one help how to grab two different images. According to opencv documentation mRgba and mRgba2 should be different.

sorry it is core.subtract() not Imgproc.subtract()

akniazi
– akniazi

2011-11-08 13:17:04 +00:00
Commented Nov 8, 2011 at 13:17 — akniazi
– akniazi, Commented Nov 8, 2011 at 13:17

Community · Accepted Answer · 2017-05-23 12:29:12Z

2

This question is an exact duplicate of

read successive frames OpenCV using cvQueryframe

You have to copy the image to another memory block, because the capture always returns the same pointer.

edited May 23, 2017 at 12:29

CommunityBot

11 silver badge

answered Nov 8, 2011 at 13:45

Sam

20.1k4 gold badges64 silver badges85 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Grabbing consecutive frames in android using opencv

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related