Question

This example on Code Project is almost exactly what I need… except the saveFrameFromVideo takes a percentage instead of a frame number…

How can I use this to extract frame X from a WMV file?

I’ve also tried FFmpeg.NET… but there weren’t any downloadable builds, and I couldn’t get the source to build…

Answer 1

You can also try AsfMojo for this task, it allows you to extract an image by time offset:

Bitmap bitmap = AsfImage.FromFile(videoFileName)
                        .AtOffset(17.34);

Internally the Media SDK and some custom stream manipulation is used to get frame accurate still frames (up to a 100 millisecond tolerance), so if you know the frame rate of your media file (i.e. 25) you can calculate the time offset of the nearest frame:

int frameX = 400; //get 400th frame
double frameRate = 25.0;
double timeOffset = frameX / frameRate;

Bitmap bitmap = AsfImage.FromFile(videoFileName)
                        .AtOffset(timeOffset);