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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.