Why Can\'t I Retrieve Frames from Video Files Using OpenCV 2.4 on Windows?

VideoCapture Not Retrieving Frames from Video Files in OpenCV 2.4 on Windows

In this article, we will address a common issue encountered by users of OpenCV 2.4 on Windows systems. Specifically, we will delve into the problem of VideoCapture being unable to capture frames from video files.

Problem Description

When using OpenCV 2.4 on Windows, the following code works as expected:

<code class="python">cap = cv2.VideoCapture(0)
print(cap.grab())</code>

However, when attempting to capture frames from a video file using the following code:

<code class="python">cap = cv2.VideoCapture(filename)
print(cap.grab())</code>

It consistently returns False, even though the path to the file is correct and valid. This issue has been observed on both Windows XP and Windows 7 machines, while on Linux (Ubuntu), the same code works flawlessly.

Solution

To resolve this issue, you need to ensure that the necessary dependencies for video decoding are available to OpenCV on Windows. This can be achieved by adding the following directory to your Windows PATH environment variable:

C:\OpenCVrdparty\ffmpeg\

Alternatively, you can manually copy the opencv_ffmpeg.dll file from the specified directory to one of these locations:

• C:Python27
• Any directory that is included in the PATH environment variable

In addition, it may be necessary to rename the opencv_ffmpeg.dll file depending on your OpenCV version and operating system (64-bit or 32-bit). Here's a guideline for renaming:

For OpenCV version X.Y.Z

• opencv_ffmpeg.dll ==> opencv_ffmpegXYZ.dll

For 64-bit OpenCV version X.Y.Z

• opencv_ffmpeg.dll ==> opencv_ffmpegXYZ_64.dll

By following these steps, you can enable OpenCV 2.4 to successfully capture and process frames from video files on Windows systems.

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