Buffer Size for SndStartFilePlay

[shen@glean.Jpl.Nasa.Gov (Sheldon Shen)]

How do you choose a buffer size for SndStartFilePlay?

IM VI (p. 22-89) mentioned that SndStartFilePlay uses double buffers
when theBuffer is set to NIL.  But it did not discuss how to choose 
the buffer size.  I found depending on the length of the sound, a small 
buffer might cause sound playing abruptly stops.  Is there a threshold for
a certain sound size?  

(When I tested the buffer size, the buffer size is always multiples of 
1024 bytes.)

Sheldon Shen