GL_RGBA doesn't gaurantee an internal storage depth, which can cause the test 
to fail if it's stored with less than 8 bits of precision. Some nVidia 
drivers would actually store with 4 bits of precision.

File dispex.c is copied from mshtml.dll. Jacek helped me to write this patch.

Kudos to pulseaudio for actually respecting buffer_time and period_time.