Why has my exported WMV video turned black?

The WMV format can force extremely low bitrates without automatic correction. This keeps the file size to a minimum – as it will discard any large “lumps” of data sent at once – but it can also give the undesired effect of discarding the entire video content, leaving only the audio.To correct this problem simply increase the bitrate when exporting. We suggest increments of +50% until you find the first usable bitrate. If you wish to further decrease the file size, decrease the bitrate slowly until the error reappears – and then return it to the previous value.