Multi-input capture is a Pro upgrade feature that allows REW to capture multiple inputs simultaneously for measurement or for the RTA. Each input can have its own calibration file. Individual SPL metering is available for the first four inputs, the level meters can show the input level for the first 16 inputs. Measurements made with multi-input capture will show an rms average of all the captured channel magnitudes with an underlay showing the span of the individual channels and can optionally include individual measurements for each channel.
The weighting of each input in the average can be configured and inputs can be aligned to a common SPL in a chosen frequency range before being averaged, useful for spatial averaging. Weighting and SPL alignment can be configured before the measurement is made (using the Configure averaging) button on the Measure dialog) or adjusted afterwards (using the Adjust average button in the SPL & Phase graph controls). Four preset weighting configurations can be saved.
RTA measurements with multi-input capture show an rms average of the individual channel magnitudes and individual traces for the first 16 inputs. The maximum number of input traces to show is configured in the View preferences, the processing and graphics capabilities of the computer may mean fewer than 16 can be displayed. RTA measurements are saved in the same format as sweep measurements allowing the same weighting and SPL alignment adjustments to be made to them after measurement have been captured. Weighting and SPL alignment can be configured before or during capture using the Configure average button on the RTA input selection dialog.
The first and last channels to be captured are selected on the Soundcard preferences, Measure dialog or RTA input dialog. The example below shows selection using ASIO drivers, a similar selection is offered for Java drivers. Note that Java drivers on Windows are limited to two channels, ASIO must be used for multi-channel devices. On macOS or Linux Java drivers offer as many channels as the interface supports.
Multi-input capture would typically be used with a mic array (such as the miniDSP UMIK-X) or a multi-channel interface with multiple analog microphones connected to it. REW captures a contiguous range of input channels. Whilst it is possible to use this feature with multiple USB microphones on Windows when using an ASIO wrapper, this is NOT recommended because:
When using the miniDSP UMIK-X there is an option on the Measure dialog to produce an average of the four mics on each UMA4 mic array as well as an overall average of all the selected inputs. The array average measurement names will be prefixed with "A1-" for the first array, "A2-" for the second and so on.