class EST_Window

In file ../include/sigpr/EST_Window.h:

class EST_Window

The EST_Window class provides functions for the creation and use of signal processing windows.

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The EST_Window class provides functions for the creation and use of signal processing windows.
Signal processing algorithms often work by on small sections of the speech waveform known as frames. A full signal must first be divided into these frames before these algroithms can work. While it would be simple to just "cut out" the required frames from the waveforms, this is usually undesirable as large discontinuities can occur at the frame edges. Instead it is customary to cut out the frame by means of a {em window} function, which tapers the signal in the frame so that it has high values in the middle and low or zero values near the frame edges. The EST_Window class provides a wrap around for such windowing operations.
There are several types of window function, including:

Rectangular, which is used to give a simple copy of the the values between the window limits.

Hanning. The rectangular window can cause sharp discontinuities at window edges. The hanning window solves this by ensuring that the window edges taper to 0.

Hamming. The hanning window causes considerable energy loss, which the hamming window attempts to rectify.

The particular choice of window depends on the application. For instance in most speech synthesis applications Hanning windows are the most suitable as they don't have time domain discontinuities. For analysis applications hamming windows are normally used.
For example code, see Windowing

typedef EST_WindowFunc Func

A function which creates a window

Functions for making windows. static void make_window(EST_TBuffer<float> &window_vals, int size, const char* name) Make a Buffer of containing a window function of specified type. static void make_window(EST_FVector &window_vals, int size, const char* name) Make a EST_FVector containing a window function of specified type. static Func* creator(const char* name, bool report_error = false) Return the creation function for the given window type

Performing windowing on a section of speech. static void window_signal(const EST_Wave &sig, EST_WindowFunc* make_window, int start, int size, EST_TBuffer<float> &frame) Window the waveform sig starting at point start for a duration of size samples. The windowing function required is given as a function pointer *make_window which has already been created by a function such as creator. The output windowed frame is placed in the buffer frame which will have been resized accordingly within the function. static void window_signal(const EST_Wave &sig, EST_WindowFunc* make_window, int start, int size, EST_FVector &frame, int resize=0) Window the waveform sig starting at point start for a duration of size samples. The windowing function required is given as a function pointer *make_window which has already been created by a function such as creator. The output windowed frame is placed in the EST_FVector frame. By default, it is assumed that this is already the correct size (i.e. size samples long), but if resizing is required the last argument should be set to 1. static void window_signal(const EST_Wave &sig, const EST_String &window_name, int start, int size, EST_FVector &frame, int resize=0) Window the waveform sig starting at point start for a duration of size samples. The windowing function required is given as a string: this function will make a temporary window of this type. The output windowed frame is placed in the EST_FVector frame. By default, it is assumed that this is already the correct size (i.e. size samples long), but if resizing is required the last argument should be set to 1. static void window_signal(const EST_Wave &sig, EST_TBuffer<float> &window_vals, int start, int size, EST_FVector &frame, int resize=0) Window the waveform sig starting at point start for a duration of size samples. The window shape required is given as an array of floats. The output windowed frame is placed in the EST_FVector frame. By default, it is assumed that this is already the correct size (i.e. size samples long), but if resizing is required the last argument should be set to 1.

Utility window functions. static EST_String description(const char* name) Return the description for a given window type static EST_String options_supported(void) Return a paragraph describing the available windows static EST_String options_short(void) Return a comma separated list of the available window types

This class has no child classes.

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This page is part of the Edinburgh Speech Tools Library documentation
Copyright University of Edinburgh 1997
Contact: speech_tools@cstr.ed.ac.uk

class EST_Window

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