Townshend Computer Tools DAT-Link - Page 88

84 Using Multiple DAT-Links
dlmrec -N 4 -I -i SPDIF -p20 test
stores 8 channels (4 stereo pairs) of 20 bit/sample data recorded from datlink0 ,
datlink1 , datlink2 , and datlink3 using their SPDIF inputs. The data is inter-
leaved, sample-by-sample, and stored in the le test . The data is self-clocking, so
only the start-time synchronization is p erformed in this case.
Although dlmrec can used with any model DAT-Link , only the DAT-Link +, ver-
sion 1.6 or later provides the facility to guarantee that the signals acquired by the
multiple units are correctly time-aligned. Prior models will delay the individual
stereo-pairs byavariable amount.
When DAT-Link +'s are used, the Sync connectors of each unit should b e wired to
an external clock as described in section 9.1.1. dlmrec then uses the READY signal
to guarantee that recording begins simultaneously for all units. If the data sources
for the units are phase-locked to each other and are aligned to an accuracy of at
least one-quarter of a sample, then this will result in the multiple channels being
exactly aligned. Otherwise, the recording from eachchannel will b egin at the same
time within +/- one sample.
If one or more units connected to the external clo ck are not needed in a particular
command, they have to be forced ready. For example, if six DAT-Link +'s are wired
to the external clo ck, and you want to record on the three rst units only, then
datlink3 , datlink4 and datlink5 should have their READY signal forced using the
command dlmkrdy :
dlmkrdy -u3
dlmkrdy -u4
dlmkrdy -u5
Then, the command
dlmrec -N3 test
waits until datlink0 , datlink1 and datlink2 are READY and stores 6 channels (3
stereo pairs), blo ck-interleaved, at 16 bits/sample. Afterwards, to release the forced
READY ,you use the commands:
dlmkrdy -u3 -c
dlmkrdy -u4 -c
dlmkrdy -u5 -c
The way the channels are recorded to the le can b e reordered using the -u option
of dlmrec . Its argument is a comma-separated list of DAT-Link + unit numb ers fol-
lowed by one of the letters: L , R ,or S . These signify left, right or stereo resp ectively.
The order of the list determines the mapping of channels to DAT-Link + units. For