The DSP Status Window shows you the complete set all of the parameters of audio input and output in MSP. You can use the DSP Status Window to set these parameters, and as a way to monitor your current audio settings.

Using the DSP Status Window, you can:

All of these options can also be changed from within your Max patch by using the adstatus object in your max patch, or by sending messages to the Max application.

The DSP Status Window includes of a set of tabs you can use to change what is displayed in the window, and a listing of all the settings associated with DSP processing in Max/MSP.

You can turn audio processing on and off using the DSP Status Window, and also toggle audio processing using the MSP UI objects ezdac~ and ezdac~, or the adc~ and dac~ MSP objects.

While some specific features and settings for using audio on your computer will vary according to the type of audio interface and audio drivers you have installed, you can access these settings in MSP using DSP Status Window.

The Driver pop-up menu in the DSP Status Window lets you view and select an audio driver for MSP. The list of available drivers will vary according to the audio drivers installed on your system. Here is a brief summary of the default options:

When you have selected the audio driver you want to use, various input (Input Channels, Input Device, and Input Source) and output (Output Channels, Output Destination, and Playthrough Input) parameter settings will become available based on the audio driver you choose.

Note: the number of input channels and output channels displayed in the DSP window are displayed with the grey attribute icon because the number of channels is driver/interface-dependent.

You can set the audio sampling rate with the Sampling Rate pop-up menu. For full-range audio, the recommended sampling rate is 44.1 kHz. Using a lower rate will reduce the number of samples that MSP has to calculate, thus lightening your computer’s burden, but it will also reduce the frequency range.

Max/MSP processes audio in by using a block of samples called a signal vector (for an introduction to how MSP works, click here). You can use the DSP Status Window to select the I/O vector size (i.e., the number of audio samples) of the block size that Max/MSP uses when working with audio input and audio output. You can also set the signal vector size - the number of samples that Max/MSP processes at a time.

The I/O Vector size and Signal Vector size in MSP are commonly expressed as powers of two. They can be set as low as 2 samples, and in most cases can go as high as the largest available I/O Vector Size for your audio driver. However, if the I/O Vector Size is not a power of 2, the maximum signal vector size is the largest power of 2 that divides evenly into the I/O vector size.

Optimizing the performance of any particular large audio patch when you are close to the limit of your CPU’s capability is a trial-and-error process that requires an understanding of how signal vector sizes and the Max scheduler interact. THe Audio I/O chapter of the MSP Tutorial contains a thorough discussion of CPU usage, the sampling rate, vector sizes and signal vectors, and Max scheduler parameters such as overdrive and audio interrupt.

When Overdrive is enabled, Max gives priority to timing and MIDI processing over screen drawing and user interface tasks such as responding to mouse clicks. If you are primarily going to be using Max for MIDI or audio processing, Overdrive should be enabled. If you are primarily going to be using Jitter, Overdrive should be disabled. You can use the DSP Status Window to set this feature.

MSP includes a non real-time driver that lets you to use MSP as a disk-based audio processing and synthesis system, removing the limit of how much processing you can do with your CPU in real time. Using the ad_nonreal driver means that Max/MSP calculates samples in MSP independently of any physical scheduling priority, allowing you to process a vector of audio using a signal path that might take your computer more than one vector's worth of real time to compute.

Patches that use the non real-time driver typically use the dsptime~ object to see how long the audio has been turned on, and pipe their output of to sfrecord~ to capture the results.

In Max/MSP, you can create a dac~ or adc~ object that uses a channel number between 1 and 512. These numbers refer to what are called logical channels. Logical channels can be dynamically assigned and reassigned to the physical device channels of a particular driver using the DSP Status window and its I/O Mappings subwindow, (you can also do this remapping using the adstatus object.

The pop-up menus labeled Input Channel 1, Input Channel 2, Output Channel 1, and Output Channel 2 allow you to map the first two logical channels of I/O in MSP (i.e. the first two outlets of the adc~ object and the first two inlets of the dac~ object) to physical channels used by your audio driver. Different audio drivers give you different options - for example, the MME driver on Windows only supports two channels, so you will normally use the default options. To map additional logical channels, use the I/O Mappings window, which you can view by clicking the I/O Mappings button at the bottom of the DSP Status window.

In addition, you can use the adstatus object from within your patch to map any of the 512 logical audio I/O channels.

The reason for using logical and physical channels is to let you create patches that use as many channels as you need without regard to the particular hardware configuration you're using. For instance, some audio interfaces use physical device channels 1 and 2 for S/PDIF input and output. If you don't happen to have a S/PDIF-compatible audio interface, you may wish to use channels 8 and 9 instead. You can simply go to the DSP Status window and choose the eighth and ninth physical channels listed in the Input and Output pop-up menus.

Logical channels in MSP are only created if there is a dac~ or adc~ object using them. In other words, if you're only using logical outputs 1 and 2, there aren't 510 unused audio streams sitting around hogging your CPU. However, since you can mix any number of logical channels to a single physical channel if necessary, you can create a complex multi-channel setup that will allow other people to hear all of your logical channels when they use it on a two-channel output device.