[Error] '_delay' was not declared in this scope该怎么改

"Error: '_delay' was not declared in this scope" 这个错误通常是当你尝试在一个作用域中使用未声明的变量或函数 '_delay' 时产生的。你需要检查以下几个步骤来解决：

1. 确保 '_delay' 是否是你当前代码块中应该有的。可能是拼写错误、大小写错误，或者是你在其他文件中定义的，在当前文件里忘记包含。

2. 检查是否有导入相关的库或头文件，如果 '_delay' 是某个特定库提供的延迟函数，需要确保已经正确引入了那个库。

3. 如果 '_delay' 是一个局部变量，确保它是在正确的上下文中声明的，比如在函数内部而不是全局范围内。

4. 如果 '_delay' 是一个自定义函数，确认它是否已经定义，并且函数体在尝试调用的地方可见。

修改方法可能包括修正拼写，添加适当的导入语句，或者调整函数的访问级别。如果你能提供具体的上下文，我可以给出更准确的建议。

相关问题

CV_THRESH_BINARY was not declared in this scope

This error message typically occurs in programming languages such as C++ or Python and indicates that the compiler or interpreter cannot find the definition for the constant or variable named "CV_THRESH_BINARY" in the current scope.

"CV_THRESH_BINARY" is a constant used in the OpenCV library, which is a popular computer vision library used for image processing and computer vision tasks. It is typically used to threshold an image using a binary thresholding method, where pixel values above a certain threshold are set to a maximum value and pixel values below the threshold are set to zero.

To resolve this error, you may need to include the appropriate header files or libraries that define the "CV_THRESH_BINARY" constant, or ensure that the variable is properly declared and initialized within your code. Alternatively, you can try using a different thresholding method or constant that is available in your programming language or library.

avdevice_register_all was not declared in this scope

这个错误通常出现在使用 FFmpeg 库时没有正确包含相关的头文件或链接相关库。可以尝试在代码中添加以下头文件：

extern "C" {
#include <libavdevice/avdevice.h>
}

如果还是无法解决问题，可以检查编译时是否正确链接了 FFmpeg 库，例如在编译命令中加入 `-lavdevice` 参数。