The manager class is fundamental in the Auditory front-end. It is responsible for, from a user request, instantiating the correct processors and signal objects, and linking these signals as inputs/outputs of each processor. In a standard session of the Auditory front-end, only a single instance of this class is created. It is with this object that the user interacts.

Processors and signals instantiation

Single request

A standard call to the manager constructor, i.e., with no other argument than a handle to an already created data object dataObj will produce an “empty” manager:

>> mObj = manager(dataObj)

mObj =

manager with properties:

    Processors: []
     InputList: []
    OutputList: []
           Map: []
          Data: [1x1 dataObject]

Empty properties include a list of processors, of input signals, output signals, and a mapping vector that provides a processing order. The Data property is simply a handle to the dataObj object provided for convenience.

Populating these properties is made via the addProcessor method already described in Computation of an auditory representation. From a given request and an empty manager, instantiating the adequate processors and signals is done following these steps:

  1. Get the list of signals needed to compute the user request, using the getDependencies function.
  2. Flip this list around such as to have the list starting with ’time’, and ending up with the requested signal. The list then provides the needed signals in the order they should be computed.
  3. Loop over the elements of the list. For each signal on the list:
    1. Instantiate a corresponding processor (two if stereo signal)
    2. Instantiate the signal that will contain the output of the processor (two if stereo)
    3. Add the signal(s) to dataObj
    4. A handle to the output signal of the previous processor on the list is stored as the current processor’s input (in mObj.InputList as well as in the processor’s Input property). If it is the first element of the list, this will link to the original time domain signal.
    5. A handle to the newly instantiated signal is stored similarly as output. This handle is stored further for the next element in the loop.
    6. A handle to the previously instantiated processor is stored in the current processor’s Dependencies property (possibly empty if first element of the list).
  4. Generate a linear mapping (vector of indexes of the processors ordered in increasing processing order).
  5. Return a handle to the requested signal to the user.

Once addProcessor called, the properties of the manager will have been populated, e.g.:

>> mObj

mObj =

  manager with properties:

    Processors: {3x2 cell}
     InputList: {3x2 cell}
    OutputList: {3x2 cell}
           Map: [1 2 3]
          Data: [1x1 dataObject]

Processors are arranged with the same convention as for signals in a data objects: they are stored in a cell array, where the first column is for left (or mono) channel, and second column for right channel. Different lines are for different processors, e.g.:

>> mObj.Processors

ans =

    [1x1 preProc      ]    [1x1 preProc      ]
    [1x1 gammatoneProc]    [1x1 gammatoneProc]
    [1x1 ihcProc      ]    [1x1 ihcProc      ]

InputList and OutputList are cell arrays of handles to signal objects. An element in one of them will correspond to the input/output of the processor at the same position in the cell array.

Handling of multiple requests

The above-described process gets more complicated when a request is placed in a non-empty manager (i.e., when multiple requests have been placed). The same steps could be used, and would result in a functioning result. However, this would likely be sub-optimal in terms of computations. If the new request has common elements with representations that are already computed, one need not recompute them.

If correctly implemented, a manager should be able to “branch” the processing, such that only new representations, or representations where a parameter has been changed, are recomputed. Achieving this relies on the findInitProc method of the manager, which is described in more details in the next subsection. This method is passed the same arguments as the addProcessor method, i.e., a request name and a structure of parameters. It will return a handle to an already existing processor in the manager that is exactly computing one of the steps needed for that request. It will return the “highest” already existing step. In other terms, it finds the point in the already existing ordered list of processors where the processing should “branch out” to obtain the newly requested feature. Knowing the processor to start from and updating accordingly the list of signals/processors that need to be instantiated, the same procedure as before can then be used in the addProcessor method.

The findInitProc method

To find an initial processor suitable in a request, this method calls the hasProcessor method of the manager and the hasParameters method of each processor. From a given request, it can obtain a list of necessary processing steps from getDependencies and run the list backwards. For each element of the list, findInitProc “asks” the manager if it has such a processor via its hasProcessor method. If yes, it calls this processor hasParameters method to verify that what the processor computes corresponds to the request. If yes, then it found a suitable initial step. If no, it moves on to the next element in the list and repeats.

Carrying out the processing

As of the current Auditory front-end implementation, the processing is linear and the processChunk methods of each individual processor are called one after the other when asking the manager to start processing (via its initiateProcessing method). The order in which the processors are called is important, as some will take as input what was other’s output. This order is stored in the property Map of the manager. Map is a vector of indexes corresponding to the lines in the Processors cell array property of the manager. It is constructed at instantiation of the processors. Conceptually, if there are N instantiated processors, the processChunk method of the manager mObj will call the initiateProcessing methods of each processor following this loop:

for ii = 1:n_proc
        % Get index of current processor
        jj = mObj.Map(ii);

        % Perform the processing by calling initiateProcessing

        if size(mObj.Processors,2) == 2 && ~isempty(mObj.Processors{jj,2})


Note the difference between indexes ii which relate to the processing order (processing first ii=1 and last ii=n_proc) and jj = mObj.Map(ii) which relate the processing order with the actual position of the processors in the cell array mObj.Processors.

[Goebbert2014]Göbbert, J. H. (2014), “Circular double buffered vector buffer (circVBuf.m),” Matlab file exchange:, accessed: 2014-10-30.