Converting .sfk files to .mp4 format.
Converting Sound Forge Pro Audio Peak Files directly to MPEG-4 Videos (.sfk to .mp4 conversion) is, per se, not possible. At least not without a workaround.
SFK files store the waveform image of WAVE Audio Files (WAV) generated by Sound Forge Pro, VEGAS Pro, or Sony digital media devices. That means that all you need to do is to get your WAV file and convert it to MP4. Check the convert WAV to MP4 entry.