I sometimes ask on Usenet or on IRC. IRC messages may get lost (although they may also be answered more quickly if there are enough users); Usenet messages are unlikely to get lost (although they may expire, someone will probably still have a copy, and in general you can still post a follow-up message to an expired article). But to try to more likely to get an answer, would be asking in more than one place, I suppose. (I think that audio/video would make it worse, though; text format would work better for these kind of things, I think.)