84
Appendix F: I/O Delays
MTRX II Input to Output Delays
The total system delay has to be large enough to accommodate for the processing latency in the unit. There is almost the same delay on
all the digital I/O, and any difference is due to an inherit difference of time it takes to sync to the different signals before samples are
available for time stamping. Digital inputs are time stamped when they enter the matrix algorithm and buffered according to the time
stamp on all outputs in the digital domain. This maintains phase coherence regardless of audio signal path and processing. Likewise, sig-
nals maintain the same phase whether they are running through the summing process or not. This is still the case for any signal routed
through an MTRX SPQ card (a DSP/FPGA expansion card for MTRX), but the whole system delay increases automatically to 7 samples
(SPQ filter processing requires an additional 2 samples).
There is an additional delay with analog I/O—AD (analog-to-digital) and DA (digital-to-analog)—due to the conversion process. This
delay varies depending on the sample rate. Once digitized, the signal is time stamped and buffered the same as with digital inputs.
The table below provides the delay in samples, based on a system delay of 5 samples, from Input to Output with Pro Tools | MTRX.
*The delay for Thunderbolt is the delay provided by the transfer from the audio hardware to the DADdriver. In addition there is the buf-
fer delay set for the audio application in use.
MTRX Input to Output delay in samples
Input
Output
DA (1fs) DA (2fs) DA (4fs) AES MADI PHD Dante Thunderbolt*
AD (1fs) 51 18 18 19 20.25 20
AD (2fs) 49 15 15 16 17.25 17
AD (4fs) 47 11 11 12 13.25 13
AES 3839415567.257
MADI 3940426678.258
PHD 3839415567.257
Dante 39.25 40.5 42.25 6.25 6.25 7.25 8.5 8.25
Thunderbolt* 4041437789.259
The delays listed above are without enabling ProMon/SPQ. If enabled, all values/channels increase by two samples, which are needed
for processing.
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