cv::VideoCapture::read cannot read any frame at all

[teongleng]

System information (version)

• OpenCV => 3.3
• Operating System / Platform => Windows 10 64 Bit
• Compiler => Visual Studio 2015

Detailed description

Steps to reproduce

Duplicate of #10377

[teongleng]

Just to make it clear:

1. My PATH (OPENCV_DIR aka C:\opencv\build\x64\vc14) is pointing to the directory %OPENCV_DIR%\bin where opencv_ffmpeg330_64.dll is located.
2. I have also make a copy of opencv_ffmpeg330_64.dll & place it next to app EXE file.
3. I have added cap.isOpened() for checking.
   But the result still the same.

Below is my updated code (cap.isOpened() added) & the result it produced:

#include "opencv2\highgui\highgui.hpp"
#include "opencv2\imgproc\imgproc.hpp"

int main()
{
	cv::namedWindow("Example 3", cv::WINDOW_AUTOSIZE);
	cv::VideoCapture cap;

	cap.open("movie.avi");

	/***** Newly Added *****/
	if (!cap.isOpened())
	{
		std::cout << "Cannot open file...\n";
		return -1;
	}

	cv::Mat frame;
	double dWidth = cap.get(CV_CAP_PROP_FRAME_WIDTH);
	double dHeight = cap.get(CV_CAP_PROP_FRAME_HEIGHT);
	std::cout << "Frame size : " << dWidth << " x " << dHeight << std::endl;
	for (;;)
	{
		cap.read(frame);
		if (frame.empty());
		{
			std::cout << "Frame empty...\n";
			break;
		}
		cv::imshow("Example 3", frame);
	}
	cv::waitKey(0);
    return 0;
}

Result (Same as before):

Frame size : 1920 x 1080
Frame empty...
Press any key to continue . . .

[alalek]

Try to run with OPENCV_VIDEOCAPTURE_DEBUG=1 environment variable.
Could you try OpenCV's video file (vtest.avi from samples/data) or share your file (or part of this file) somehow?

[teongleng]

Hi Sir,

• Can you please provide me the step to run with OPENCV_VIDEOCAPTURE_DEBUG=1 environment variable?
  Is it go to Control Panel > System > Advanced system settings > Advanced Tab > Environment Variables... > System variables > Path > Edit... > New > Type "OPENCV_VIDEOCAPTURE_DEBUG=1" ?

• I have uploaded the entire Example 2-3.cpp file, all code is similar to the previous comment.
  Example 2-3.zip

• If you need the entire project directory you can download from below link:
  https://1drv.ms/f/s!AnE7WULnZpCwjxM9eDEpK0WU90nC

• Please import below global property sheets into VS IDE for debugging:
  Global Property Sheets.zip

Thank you.

[teongleng]

Hi Sir,
I've tried to run the program again, this time with OPENCV_VIDEOCAPTURE_DEBUG=1 included inside VS2015 IDE (Project > Properties... > Configuration Properties > Debugging > Environment).

Code:
#include "stdafx.h"
#include
#include "opencv2\highgui\highgui.hpp"
#include "opencv2\imgproc\imgproc.hpp"

int main()
{
cv::namedWindow("Example 3", cv::WINDOW_AUTOSIZE);
cv::VideoCapture cap;

cap.open("vtest.avi");

/***** Newly Added *****/
if (!cap.isOpened())
{
	std::cout << "Cannot open file...\n";
	return -1;
}

cv::Mat frame;
double dWidth = cap.get(CV_CAP_PROP_FRAME_WIDTH);
double dHeight = cap.get(CV_CAP_PROP_FRAME_HEIGHT);
std::cout << "Frame size : " << dWidth << " x " << dHeight << std::endl;
for (;;)
{
	cap.read(frame);
	if (frame.empty());
	{
		std::cout << "Frame empty...\n";
		break;
	}
	cv::imshow("Example 3", frame);
}
cv::waitKey(0);
return 0;

}

Result:
VIDEOIO(cvCreateFileCapture_FFMPEG_proxy (filename)): trying ...
VIDEOIO(cvCreateFileCapture_FFMPEG_proxy (filename)): result=000002A75A90D060 ...
Frame size : 768 x 576
Frame empty...
Press any key to continue . . .

Thank you.

[alalek]

VIDEOIO(cvCreateFileCapture_FFMPEG_proxy (filename)): result=000002A75A90D060

This mean that ffmpeg backend is selected and opencv_ffmpeg330_64.dll is loaded successfully.

[alalek]

In next time you should start from using samples from OpenCV.
Your sample has several issues:

• invalid semicolon (;) in this line:

+std::cout << frame.size() << std::endl; // check real frame size
-if (frame.empty());
+if (frame.empty())
{

• "cv::waitKey(0);" must be placed right after "cv::imshow()" with some non-zero delay:

cv::imshow("Example 3", frame);
cv::waitKey(30); // ~30 fps

Usage questions should go to Users OpenCV Q/A forum: http://answers.opencv.org
Only confirmed issues should be reported here. This tracker is for issues and bugs that needs fix in OpenCV.

[teongleng]

Hi Sir, Thanks for your help and it's really a great experience learning from you. Thank you and have a wonderful Merry Christmas. Your sincerely, Teongleng On Dec 22, 2017 6:33 PM, Alexander Alekhin <notifications@github.com> wrote: In next time you should start from using samples from OpenCV. You sample have several issues: * invalid semicolon in this line: +std::cout << frame.size() << std::endl; -if (frame.empty()); +if (frame.empty()) { * "cv::waitKey(0);" must be placed right after "cv::imshow()" with some non-zero delay: cv::imshow("Example 3", frame); cv::waitKey(30); // ~30 fps Usage questions should go to Users OpenCV Q/A forum: http://answers.opencv.org Only confirmed issues should be reported here. This tracker is for issues and bugs that needs fix in OpenCV. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub<#10378 (comment)>, or mute the thread<https://github.com/notifications/unsubscribe-auth/AhIu-RXWxynL94wFARo6QKnuIBVvAX_fks5tC4V_gaJpZM4RKB85>.