try (40/1024)*1000=25600 or (40/2048)*1000=51200 if your soundcard can do this!
so if your block~ is set to 1024, a sfrate of 25.6KHz should work, if 2048 then sfrate=51.2KHz.
Happy pix-ing
Ed Kelly The Micheal Tippett Centre Bath Spa University College Newton Park Newton St Loe Bath BA2 9BN UK