B4A Library OpenCV 3.x

JordiCP · Jul 6, 2022

According to the code I see, it happens because you are processing a copy of the preview Mat but not drawing this processed copy it anywhere (it only happens automatically when you use JavaCameraView) --> check the example that was made with cameraEx Class and you'll notice that, once processed, the resulting Mat was converted to a bitmap which is drawn/attached to a view

--EDIT--

Also, these lines are wrong (assigning a bitmap to mbm and then initting it)

B4X:

mbm = cam.GetPreviewBitmap(480,640)
'    Log(cam.PreviewSize.Height& "  " & cam.PreviewSize.Width)
   mbm.InitializeMutable(480,640)

biometrics · Aug 1, 2022

JordiCP said:

(edit, didn't see the reply until it was too late

)

Hi roberto,

Out-of-the-box OpenCV for Android build only has support for MJPEG encoded videos in .AVI container (even if the API allows so many options ... I was also surprised at the beginning). HERE you can read a bit more about it.

So I would check first if your file is MJPEG encoded.

If the answer is positive (i.e., your video file is already MJPEG encoded), please test your video with the attached code. It is an example that I was just preparing. You will see that there are some things slightly different that in your code ( I think the initialize2() method that you are using is not correct in my library and have to fix or remove it)
If not, you should convert it either externally on your PC, or internally with some transcoder (I tested not much ago @moster67 ffmpeg and it worked perfect for me)

In the future I may add internal ffmpeg support (if I find time and get how to do it), or an internal H264 encoder/decoder if I find a nice example to integrate. But it is not in my priority list since there are workarounds, and is not a limitation of my wrapper but of the standard OpenCV for Android build.

B4X:

#Region  Project Attributes
   #ApplicationLabel: OCV VideoCapture
   #VersionCode: 1
   #VersionName:
   'SupportedOrientations possible values: unspecified, landscape or portrait.
   #SupportedOrientations: landscape
   #CanInstallToExternalStorage: False
#End Region

#Region  Activity Attributes
   #FullScreen: False
   #IncludeTitle: True
#End Region


Sub Process_Globals
   'These global variables will be declared once when the application starts.
   'These variables can be accessed from all modules.
 
   Dim t As Timer
 
   Dim VIDEO_SRC As String = "myvideo9.avi"         'Has to be MJPEG encoded.
 
End Sub

Sub Globals
   'These global variables will be redeclared each time the activity is created.
   'These variables can only be accessed from this module.
   Dim ocl As OCVOpenCVLoader
 
   Dim mCore As OCVCore
   Dim mImgProc As OCVImgproc

   Dim MyMatBGR As OCVMat
 
   Dim mVideoCapture As OCVVideoCapture
 
   Dim myVideoCaptureMat As OCVMat
   Dim myVideoCaptureBitmap As Bitmap
 
   Dim capturing As Boolean=False
   Dim P As Panel
   Dim btnStartStop As Button
 
End Sub

Sub Activity_Create(FirstTime As Boolean)
   'Do not forget to load the layout file created with the visual designer. For example:

   ' As it is a demo, set everything to 640X480, since we know the video has that size
   P.Initialize("")
   Dim HH As Int = 80%Y
   Dim WW As Int = HH*640/480       'Keep aspect ratio for this example.
   Activity.AddView(P,(100%X-WW)/2,(100%Y-HH)/2,WW,HH)     ' Center screen

   myVideoCaptureBitmap.InitializeMutable(640,480)
   P.SetBackgroundImage(myVideoCaptureBitmap)
 
   'Control Button
   btnStartStop.Initialize("btnStartStop")
   btnStartStop.Text="Start"
   Activity.AddView(btnStartStop,20dip,20dip,80dip,40dip)
 
   t.Initialize("t",500)
 
End Sub

Sub Activity_Resume

End Sub

Sub Activity_Pause (UserClosed As Boolean)
   capturing=False
   mVideoCapture.release
   t.Enabled=False
   Activity.Finish
End Sub

Sub btnStartStop_Click
 
   If Not(capturing) Then
     InitVideoCapture
   Else
     mVideoCapture.release
     btnStartStop.text="Start"
     t.Enabled=False
     capturing=False
   End If

End Sub


Sub t_tick
   If Not(t.Enabled) Then Return     'just in case it was a pending event
   If Not(capturing) Then Return
   Log("Tick")
   If mVideoCapture.isOpened Then
     If (mVideoCapture.read(myVideoCaptureMat)) Then
    
       If Not(myVideoCaptureMat.empty) Then 'really needed? should test
    
         'From https://github.com/opencv/opencv/issues/4974
         '// get some meta data about frame.
         'double fps = capture.get(Videoio.CAP_PROP_FPS);
         'double frameCount = capture.get(Videoio.CAP_PROP_FRAME_COUNT);
         'double h = capture.get(Videoio.CAP_PROP_FRAME_HEIGHT);
         'double w = capture.get(Videoio.CAP_PROP_FRAME_WIDTH);
         'double posFrames = capture.get(Videoio.CAP_PROP_POS_FRAMES);
         'double posMsec = capture.get(Videoio.CAP_PROP_POS_MSEC);
         'double speed = capture.get(Videoio.CAP_PROP_SPEED);
    
         Log("mVideoCapture has read!" & myVideoCaptureMat.rows &" "&myVideoCaptureMat.cols)
         Dim mUtils As OCVUtils
         mUtils.matToBitmap(myVideoCaptureMat, myVideoCaptureBitmap,False)
         P.Invalidate
    
       End If
     End If
   Else
     Log("mVideoCapture is not open")
   End If
 
End Sub


Sub InitVideoCapture
 
   mVideoCapture.Initialize1(File.Combine(File.DirRootExternal,VIDEO_SRC),0)
   If mVideoCapture.isOpened Then
     Log("VideoCapture file correctly opened")
     t.Enabled=True
     capturing=True
     btnStartStop.Text = "Stop"
   Else
     ToastMessageShow("VideoCapture failed to open.",True)
     capturing=False
     btnStartStop.Enabled = False
   End If
 
End Sub

Hi @JordiCP,

I can't get this to work. I believe my .avi is correctly encoded but I'm getting False on .isOpened. Could you please make myvideo9.avi available so I can test with the same file you used.

JordiCP · Aug 1, 2022

If I remember correctly, it had to be first copied to the internal libraries folder and wait for a while since the copy operation is async.
Can you check it?

I'll be able to look for the video or any other that works tomorrow

biometrics · Aug 1, 2022

JordiCP said:
If I remember correctly, it had to be first copied to the internal libraries folder and wait for a while since the copy operation is async.
Can you check it?

I'll be able to look for the video or any other that works tomorrow

I copied my videos to File.DirRootExternal manually. So it's been there for a while before I ran the code, so I don't think that's a problem. Would appreciate your working .avi. If that works then my colleague that's a video encoding expert can inspect it and get the exact profile we need.

Edit: Added a File.Exists check to make sure.

JordiCP · Aug 1, 2022

If it isn't due to file access permissions issues, then the only thing I can think of is indeed an issue with the file format or perhaps the file size (too big?)

As said, I'll be able to look at it tomorrow, but I'm not even sure that I have my original avi file, although it should work with others.

biometrics · Aug 1, 2022

JordiCP said:
If it isn't due to file access permissions issues, then the only thing I can think of is indeed an issue with the file format or perhaps the file size (too big?)

As said, I'll be able to look at it tomorrow, but I'm not even sure that I have my original avi file, although it should work with others.

Thanks for the clue, a smaller file is working. Not sure if it's the file size, bit rate, aspect ratio or what. They are all different. The latest working file is 8MB, 720x576, 25 fps.

biometrics · Aug 1, 2022

Managed to get it to work with any video by converting with ffmpeg:

B4X:

ffmpeg -i input.mp4 -vcodec mjpeg output.mjpeg
ffmpeg -i output.mjpeg -vcodec mjpeg output.avi

Though that produces low bit rate files at the original high resolution, so I used the -q:v parameter to keep the video quality high and the -s to reduce the size.

B4X:

ffmpeg -i input.mp4 -vcodec mjpeg -q:v 1 -s 640x360 output.mjpeg
ffmpeg -i output.mjpeg -vcodec mjpeg -q:v 1 -s 640x360 output.avi

I find the OpenCV decoding to be very slow. Not sure why...

JordiCP · Aug 1, 2022

biometrics said:
I find the OpenCV decoding to be very slow. Not sure why...

Yes. I guess it's due to the fact that, since ffmpeg itself is not a part of Opencv, it is included in some builds as a pre-compiled 3rd party binary (with limited decoding options, possibly due to licenses not being the same, and not necessarily with the fastest build options ...in short, decoding itself is not the main scope of Opencv).

I think that a custom build of all the project with a full and optimized ffmpeg could perhaps improve it, but that's not a straightforward change

biometrics · Aug 1, 2022

JordiCP said:
Yes. I guess it's due to the fact that, since ffmpeg itself is not a part of Opencv, it is included in some builds as a pre-compiled 3rd party binary (with limited decoding options, possibly due to licenses not being the same, and not necessarily with the fastest build options ...in short, decoding itself is not the main scope of Opencv).

I think that a custom build of all the project with a full and optimized ffmpeg could perhaps improve it, but that's not a straightforward change

We just really wanted to go record real world videos as tests and play them in the office. But we'll just use a Windows PC to play the videos and point the Android camera at it. Will also work, just not very elegant. So not a big deal.

lingqdy1 · Tuesday at 1:22 AM

gezueb said:

Hi Jordi, I am refering to your Example ImageManipulation2 where the points of a circle are detected. This is the part of your code:

B4X:

        Dim circles As OCVMatOfPoint3f
        circles.Initialize  
'dp=1 --> 算法的比例因子。1=从原始图像开始
'minDistance --> 以防止误报。但是，如果圆是同心的，则将此系数保持尽可能小
'mImgProc.HoughCircles1（ tmpMatGray，circles，mImgProc.HOUGH_GRADIENT，1,10）
mImgProc.HoughCircles（tmpMatGray，circles，mImgProc.HOUGH_GRADIENT，1.0d，10,150,100,20,240）
'函数 HoughCircles 返回一个 3 点 （x，y，radius） 的数组
日志（circles.rows&“ ”&circles.cols&“ ”&circles.depth）
将 allCircles（） 调暗为 OCVPoint3= circles.toArray（）
对于 k=0 到 allCircles.Length-1

Log（“检测到的圆： x=”&allCircles（k）.x &“ y=”& allCircles（k）.y &“ radius=”& allCircles（k）.z）
[/代码]
我想检测[B]线而不是圆，[/B]但我无法弄清楚线的必要声明。没有 OCVMatOfPoint4f（用于开始和结束坐标）或 OCVMatOfLine。你能帮我申报吗？
谢谢！
[/QUOTE]
这是一行

B4A Library OpenCV 3.x

Attachments

JordiCP

Expert

biometrics

Active Member

JordiCP

Expert

biometrics

Active Member

JordiCP

Expert

biometrics

Active Member

biometrics

Active Member

JordiCP

Expert

biometrics

Active Member

lingqdy1

New Member

Attachments

Similar Threads