wmv2 @ 0xb42400 warning, clipping 1 dct coefficients to -255..255

Question

[wmv2 @ 0xb42400] warning, clipping 1 dct coefficients to -255..255

I'm modifying some code in a C API that interacts between FFmpeg and and an AS3 Air application to encode a video after creating something.

WMV was working okay earlier but now I've set things back I'm getting this very peculiar warning coming from the c library but it doesn't make any sense and googles not providing many answers.

I was wondering if anyone out there knew what this warning was about? When the file comes back to me it's totally empty with 0 frames. I must have changed something so I'm comparing the file from a few days ago with this one looking for anything that may have caused it to no longer work. But I was wondering if anyone had any better ideas than blindly looking through old and new code.

Answer 1

This particular warning comes from the FFmpeg core code. It is just warning that it had to perform an adjustment on some bits of the video stream in order to successfully decode it. It might help to understand that the WMV2 algorithm (being decoded, per your error message) was reverse engineered from binary code and reimplemented in FFmpeg, which is why things like this slip through the cracks.