PCI-822 User’s Guide
49
— IRQ Latency —
This statistic indicates the maximum number of audio samples
that have elapsed between the time the WaveCenter/PCI hardware
asked for service and the time Windows began to process the
request. Typically it’s less than 5.
Correlating the system’s response time to interrupts with other system
activity will help you determine if there are other installed devices that
prevent WaveCenter/PCI from being serviced efficiently. To calculate
the absolute latency (accurate to within one sample), divide the IRQ
latency by the current sample rate.
— IRQ Misses —
Normally, this should be zero. An IRQ miss means the WaveCenter/PCI
driver wasn’t given enough time to transfer audio between your PC
and the WaveCenter/PCI hardware, a severe problem indicating that
something in the system is causing gross timing latencies that can’t
be overcome. The result can be brief audio dropouts or pops. Try to
determine whether another device is active when the IRQ misses
occur, and then correct the situation by removing that device or by
not using it while also trying to transfer audio.
— Input Overruns —
This indicates how many errors occurred when WaveCenter/PCI was
ready to transfer newly-recorded information to an application, but
the application hadn’t supplied a buffer in which to write the audio
data. Input overruns are generally caused by an overloaded CPU or a
disk system that can’t keep up with the audio applications.
— Output Underruns —
This indicates the number of times that the driver ran out of data to
send to the digital audio outputs. Generally, it means that the CPU or
disk system couldn’t keep up with the real-time demands of the
application. It’s normal to see a “blip” when playback stops, but an
output underrun in the middle of playback indicates a problem.
