21.5 Access strategies
Three basic accessing strategies are available when using
diphone databases. They are designed to optimise access time, start up
time and space requirements.
direct- Load all signals at database init time. This is the slowest startup but
the fastest to access. This is ideal for servers. It is also useful
for small databases that can be loaded quickly. It is reasonable for
many group files.
dynamic- Load signals as they are required. This has much faster
start up and will only gradually use up memory as the diphones
are actually used. Useful for larger databases, and for non-group
file access.
ondemand- Load the signals as they are requested but free them if they are not
required again immediately. This is slower access but requires low
memory usage. In group files the re-reads are quite cheap as the
database is well cached and a file description is already open for the
file.
Note that in group files pitch marks (and LPC coefficients) are
always fully loaded (cf. direct), as they are typically
smaller. Only signals (waveform files or residuals) are potentially
dynamically loaded.