VideoWriter: failed to load codec library, yet video is processed and saved

[michalgrzyska]

Summary of your issue

I receive an error that a codec lib is not found, yet my video is processed correctly.

Environment

win-64

What did you do when you faced the problem?

I am just trying to use VideoCapture with avc1, process frames and use VideoWriter. Regular operation.
I was using mp4v but those videos cannot be used in Messenger, WhatsApp etc.

Example code:

using VideoCapture capture = new(inputPath);
using VideoWriter writer = new(outputPath, FourCC.FromString("avc1"), capture.Fps, captureSize);

using Mat frame = new();

// ... blah blah blah, some loop processing video
{
    writer.Write(frame);
}

Output:

Failed to load OpenH264 library: openh264-1.8.0-win64.dll
        Please check environment and/or download library: https://github.com/cisco/openh264/releases

[libopenh264 @ 000002500358f440] Incorrect library version loaded
[ERROR:[email protected]] global cap_ffmpeg_impl.hpp:3194 open Could not open codec libopenh264, error: Unspecified error (-22)
[ERROR:[email protected]] global cap_ffmpeg_impl.hpp:3211 open VIDEOIO/FFMPEG: Failed to initialize VideoWriter

What did you intend to be?

No error output. Video is processed anyway.