User`s guide

User's Guide DIGI96/8 PST © RME

12.2 Buffer Size - Latency

The Buffer Size value in the RME DIGI Settings dialog determines the latency (in this case the

delay) between the audio application and the DIGI96 series as well as general system stability.

The higher the value, the more tracks can be recorded and played back simultaneously and the

longer the system takes to react.

In RME DIGI Settings, ASIO, 4 different buffer sizes are available: 6 ms 24 bit, 11 ms 16 bit,

23 ms 24 bit and 46 ms 16 bit.

There is a simple relationship between the resolution of the ASIO host (Cubase etc.) and the

driver. If one of both is set to 16 bit the resolution is limited to 16 bit. Bits 17 to 24 will be trun-

cated. So when the driver uses 16 bit and Cubase is set to 24 bit only 16 bit will be transferred

to Cubase. When the driver uses 24 bit and Cubase is set to 16 bit, the additiona information in

bits 17 to 24 will be lost. As the real latency depends on the used sample rate the values are

different for different sample rates:

Choice Buffer size Resolution 44.1 kHz 48 kHz 88.2 kHz 96 kHz

46 ms/16 bit 2048 s 16 bit 46.4 ms 42.7 ms 23.2 ms 21.3 ms

23 ms/32 bit 1024 s 32 bit 23.2 ms 21.3 ms 11.6 ms 10.7 ms

11 ms/16 bit 512 s 16 bit 11.6 ms 10.7 ms 5.8 ms 5.3 ms

6 ms/32 bit 256 s 32 bit 5.8 ms 5.3 ms 2.9 ms 2.7 ms

Please note that the given latency describes only one way. The complete path through the

computer (record plus playback, monitoring) gives double values.

The mode 6 ms often causes crackling and drop outs when used with harddisk based recording,

but operates flawlessly when using realtime Synthesizers or pure signal processing (Live Input

mode). 11 ms are only recommended in 2 channel operation. Else we STRONGLY recommend

to use 46 ms to achieve the highest reliability and security in operation. The 24 bit modes

should only be used when really needed, as they not only halve the buffer size (see above), but

also produce a higher system load and less reliable system behaviour.

12.3 Performance

The 'Audio Performance' settings are especially important. Firstly, the number of channels

should be changed to 8, so that all the DIGI96/8 series inputs can be accessed.

A very common problem is insufficient hard disk perfor-

mance. If the first track is missing while recording multiple

tracks, or the error message ‘Audio: Record Error’ appears,

the disk sub-system is too slow i.e. it is unable to write the

audio data to the disk quickly enough. The problem can

almost always be remedied by changing ‘Disk Block Buffer

Size’ from the default 64kB to 256kB.

This is especially true if you want to record more than 8

tracks at the same time (multi-card operation). Recording

more than 8 tracks is in most cases only possible after changing ‘Disk Block Buffer Size’ to

256kB (depending on your computer). Please note that these parameters are only updated after

clicking on ‘Apply’.

The heyday of (expensive) SCSI hard disks in high-speed audio workstations is over. Today’s

cheap high-capacity EIDE disks allow continuous transfer rates of well over 5 MB per second.

In practical terms, this is more than enough to record far more than 8 simultaneous tracks using

Cubase and the DIGI96 series!