User guide

MS-DMT Guide v1.04
Released 05-30-2014
50
Although PC sound devices appear to support different sample rates, they actually have only
one raw hardware sample rate which is the maximum rate that can be used for modem
applications and achieve the effect of lower (and some times higher) sample rates by means of
sample rate conversion. Such conversion is performed by the sound device driver and cannot be
monitored or disabled by application software. The sample rate conversion may introduce
certain low-level distortions to the signal which preclude usefulness for modem applications,
this is especially true of up conversion. In addition, most sound device drivers provide user
selected levels of sample conversion to mitigate overhead in processing.
Should your sound device support a higher native maximum sample rate (e.g. 96k or better) you
must select the best quality sample rate conversion in the sound device driver setup. However
the use of sample conversion from a lower native raw sample rate, such as 44.1k or lower to
achieve 48k must be avoided. In addition, should your sound device provide for Hardware
Acceleration in its driver parameters, select full acceleration. To check these parameters select