Reputation: 111
I want to extract all frames from a short .mp4 video and save them as images to folder. But when I call a function cv::VideoCapture::read() it fails to extract a frame. What is the problem with my code?
#include <iostream>
#include <string>
#include <opencv2/opencv.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/videoio.hpp>
int main(int argc, const char * argv[]) {
cv::VideoCapture cap("test.mp4");
if (!cap.isOpened()) {
std::cout << "Cannot open the video file.\n";
return -1;
}
for (int frame_count = 0; frame_count < cap.get(cv::CAP_PROP_FRAME_COUNT); frame_count++) {
cap.set(cv::CAP_PROP_POS_FRAMES, frame_count);
cv::Mat frame;
if (!cap.read(frame)) {
std::cout << "Failed to extract a frame.\n";
return -1;
}
std::string image_path = "frames/" + std::to_string(frame_count) + ".jpg";
cv::imwrite(image_path, frame);
}
return 0;
}
My output is always "Failed to extract a frame.".
Upvotes: 1
Views: 2769
Reputation: 519
On the tutorial you provided above, there is an instruction:
Uncheck WITH_FFMPEG
ffmpeg library contains mp4 codecs, you need to check WITH_FFMPEG
and USE_FFMPEG
in order to read .mp4 and many other formats.
Upvotes: 1