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The DSP Status Window
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.

Viewing the DSP Status Window
You can also double-click on any dac~ or adc~ object in a locked Patcher window.

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.

Getting information about a setting

Changing the value of a Setting

Audio processing and your system
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.

Enabling/disabling audio processing using the DSP Window
Note: You must have placed an MSP object in a patcher to be able to turn audio on or off using the DSP Window. If no MSP objects have been instantiated, audio will turn itself off immediately.

Enabling/disabling audio processing using MSP objects
Audio is disabled by sending the messages 0 or stop to a dac~ object.
If you want to only turn on audio processing for a specific patcher window, use the startwindow message sent to the dac~ object.

Configuring MSP audio for your system
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:
Selecting an audio driver
This menu lists all the audio drivers installed on and available for use with Max/MSP. When you choose a driver from the menu, it becomes your default audio driver, and will remain so the next time you launch Max.

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.
Configuring audio system inputs and outputs
These menu lists all the input and output sources and destinations available for use with your audio driver. When you choose a source or destination from the menu, it becomes your default setting, and will remain so the next time you launch Max.
The Playthrough Input option is available on Macintosh non-Intel systems only. This checkbox lets you choose whether or not the input device is ‘monitored’ directly through to the output. When playthrough is enabled, the dry signal from the input source will play through to the output mixed in with any processed signal you may be sending to the output in MSP. Disabling playthrough will enable you to control how much (if any) dry signal from the audio input is routed to the output. This option can be changed in MSP on Macintosh by sending a message to the dsp object to change it.

Monitoring CPU usage
Three fields in the DSP Status window monitor the amount of signal processing MSP is currently doing.
CPU Utilization displays a rough estimate of how much of your computer's CPU is being allocated for crunching audio in MSP.
The number of Function Calls gives an approximate idea of how many calculations are being required for each sample of audio.
The number next to Signals Used shows the number of internal buffers that were needed by MSP to connect the signal objects used in the current signal network.

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.

Setting the audio sampling rate

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.

Setting the I/O and Signal Vector Sizes
Some audio interface cards do not provide a choice of I/O Vector Sizes. There are also some ASIO drivers whose selection of I/O Vector Sizes may not conform to the multiple-of-a-power-of-2 limitation currently imposed by MSP's ASIO support. In some cases, this limitation can be remedied by using the ASIO driver at a different sampling rate.

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.

Enabling/disabling Overdrive

Processing audio in non real-time
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.

Using the non real-time driver

Logical Input and Output Channels
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.

Mapping an output pair
The output you select will be used as the outlet for channel 1 or 2 for the dac~ object, and will become the new default physical outputs.

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.

Assigning multiple logical channels to a single physical channel