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<title>tkSnack manual v2.2</title>
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<h1> Snack manual, version 2.2</h1>
<h2> Installing Snack</h2>
First you need to install Snack according to its installation instruction.
In order to use Snack you need to put the file tkSnack.py somewhere in your
Python path.
<h2> Using Snack: an overview</h2>
<h3> Initializing</h3>
You need to use Tkinter in order to use Snack. Even if you don't use any
GUI elements that Tkinter offers, you will still need an active Tk object
in your program. In order for Snack to identify the Tk object it should use,
you will need to run the <tt>initializeSnack</tt> procedure.
<p>The beginning of a program that uses Snack might look like: </p>
<blockquote>
<pre>from Tkinter import *<br>root = Tk()<br><br>import tkSnack<br>tkSnack.initializeSnack(root)<br><br># Now you can use tkSnack commands and objects<br># ...</pre>
</blockquote>
<h3> Using Sound objects</h3>
You create sound objects the same way you create any Python objects.
<blockquote>
<pre>mysound = tkSnack.Sound()</pre>
</blockquote>
Since we gave no additional arguments, the sound object created by this will
contain no sound data. We can give it some data in a number of ways -- by
recording from the current input channel, by reading from a file, and so
on.
<p>Let's try reading from a file. If you're using Windows, you have at least
a few WAV files sitting conveniently on your hard drive. (If you're using
another operating system, you'll have to locate your own sound files to read
from :-).) </p>
<blockquote>
<pre>mysound.read('c:/windows/media/chord.wav')</pre>
</blockquote>
Now for the moment of truth. Try playing your sound with:
<blockquote>
<pre>mysound.play()</pre>
</blockquote>
You can create a new sound object and load a file in the same step using
the "load" option:
<blockquote>
<pre>tada = tkSnack.Sound(load='c:/windows/media/tada.wav')<br>tada.play()</pre>
</blockquote>
(Note: Another possibility is to use <tt>tkSnack.Sound(file='filename')</tt>
. Using <tt>file</tt> instead of <tt>load</tt> will "link" the disk file to
the sound object instead of immediately loading it into memory. This will
limit what you can do to the object, since a number of Snack's usual sound
methods are only available to "in-memory" sounds.)
<p>You can perform a number of manipulations on the sounds objects. For example,
let's tack a couple of copies of the Windows chord sound onto the end of
the ta-da sound. Then we'll delete a few thousand samples from the middle
of the sound (those between sample 10,000 and 40,000), and finally reverse
the sound. </p>
<blockquote>
<pre>tada.concatenate(mysound)<br>tada.concatenate(mysound)<br>tada.play()<br>tada.cut(start=10000, end=40000)<br>tada.play()<br>tada.reverse()<br>tada.play()</pre>
</blockquote>
We can write the sound back to a disk file, and even magically switch the
format.
<blockquote>
<pre>tada.write('mangled-tada.au')</pre>
</blockquote>
<h3> Audio and mixer controls</h3>
Snack has two objects that control aspects of your computer's sound system.
The <tt>audio</tt> object gets and sets properties of the sound devices. To
find out what the available input devices on your computer are and what sample
rates the current input device can record at, try:
<blockquote>
<pre>tkSnack.audio.inputDevices()<br>tkSnack.audio.rates()</pre>
</blockquote>
To turn the output volume up or down to 30%, try:
<blockquote>
<pre>tkSnack.audio.play_gain(30)</pre>
</blockquote>
The <tt>mixer</tt> object controls various aspects of your computer's sound
mixers, such as which input jack is currently being used and whether it's
recording in stereo or mono.
<h3> New canvas objects</h3>
Snack provides three new kinds of items that can be drawn on Tkinter Canvases:
<ul>
<li> <b>waveform</b>: a raw graph of the sound data, i.e., time on the x-axis
and sample amplitude on the y-axis.</li>
<li> <b>section</b>: a power spectrum of the sound (at a given time), as
calculated by Fast Fourier Transform, i.e., frequency on the x-axis and amplitude
on the y-axis.</li>
<li> <b>spectrogram</b>: a spectrogram of the sound, i.e., time on the
x-axis, frequency on the y-axis, and amplitude represented by the darkness
of the pixel.</li>
</ul>
These items have the same options as regular Tkinter Canvas items like lines,
arcs, etc., and some of their own. Try:
<blockquote>
<pre>c = tkSnack.SnackCanvas(root, height=400)<br>c.pack()<br>c.create_waveform(0, 0, sound=mysound, height=100, zerolevel=1)<br>c.create_spectrogram(0, 150, sound=mysound, height=200)</pre>
</blockquote>
<h2> The Sound class</h2>
<h3> <a name="soundoptions"></a>Options</h3>
The following attributes may be specified using optional arguments in the
intialization of the sound object. They may be read or set after initialization
by using the methods <b>cget</b> and <b>config</b>/<b>configure</b>. They
may also be read or set by treating the sound object as a dictionary, e.g.,
<blockquote>
<pre>mysound["encoding"] = "Lin32"</pre>
</blockquote>
The options:
<dl>
<dt> <b>name</b> =<i>identifier</i></dt>
<dd> what name Tcl knows your sound under. Not terribly useful inside Python.</dd>
<dt> <b>load</b> =<i>filename</i></dt>
<dd> specifies that the file named by <i>filename</i> should be read into
memory after creating the sound. (Using this option allows you to use the
in-memory manipulation methods of the Sound object.)</dd>
<dt> <b>file</b> =<i>filename</i></dt>
<dd> specifies the filename of an on-disk file that should be linked to
the sound. (Using this option means that many of the in-memory manipulation
methods of a Sound object will not be useable.)</dd>
<dt> <b>channel</b> =<i>channel-name</i></dt>
<dd> specifies that audio data resides on a channel which should be linked
to the sound. In these cases the audio data is not loaded into memory, which
is useful when playing large files or when using streaming audio. However,
the Snack canvas types, e.g., waveforms, cannot be linked to sounds of these
types.</dd>
<dt> <b>frequency</b> =<i>integer</i></dt>
<dd> The sampling rate of the sound in samples per second.</dd>
<dt> <b>channels</b> =<i>x</i></dt>
<dd> how many channels the sound uses. Values should be an integer greater
than or equal to 1, or <tt>"Mono"</tt> or <tt>"Stereo"</tt>.</dd>
<dt> <b>encoding</b> =<i>encoding-name</i></dt>
<dd> Possible values for the encoding format of the sound are:</dd>
<ul type="">
<li> "Lin16"</li>
<li> "Lin8"</li>
<li> "Lin8offset"</li>
<li> "Lin24"</li>
<li> "Lin32"</li>
<li> "Float"</li>
<li> "Alaw"</li>
<li> "Mulaw"</li>
</ul>
<dt> <b>fileformat</b> =<i>format-name</i></dt>
<dd> Current supported file formats are the following. (These formats can
be read -- not all of them can be <emph>written</emph>.)</dd>
<ul type="">
<li> "WAV"</li>
<li> "MP3"</li>
<li> "AU"</li>
<li> "SND"</li>
<li> "AIFF"</li>
<li> "SD"</li>
<li> "SMP"</li>
<li> "CSL" (will usually have the extension .nsp)</li>
<li> "RAW" binary</li>
</ul>
<dt> <b>skiphead</b> =<i>n</i></dt>
<dd> is used to skip an unknown file header of length <i>n</i> bytes.</dd>
<dt> <b>byteorder</b> =<i>string</i></dt>
<dd> <tt>"littleEndian"</tt> or <tt>"bigEndian"</tt></dd>
<dt> <b>guessproperties</b> =<i>boolean</i></dt>
<dd> specifies that Snack should try to infer properties such as byte order,
sample encoding format, and sample rate for raw files by analyzing the contents
of the files. Byte order is almost always detected correctly.</dd>
<dt> <b>buffersize</b> =<i>integer</i></dt>
<dd> specifies the size of the internal buffer in samples, for channel-based
sounds.</dd>
<dt> <b>precision</b></dt>
<dd> specifies whether sound data should be handled using single or double
precision internally.</dd>
</dl>
<h3> Methods</h3>
<h4> append (<i>binary-string</i>)</h4>
Appends binary string data to the end of this sound. The same
options apply as for the <i>read()</i> command.
<h4> cget (<i>option</i>)</h4>
Retrieves the value of an option for the sound. The possible options are
listed <a href="#soundoptions">above</a>. It is also possible to access the
options by treating the sound object as a dictionary, i.e., the following
two expressions are equivalent:
<blockquote>
<pre>mysound["encoding"]<br>mysound.cget("encoding")</pre>
</blockquote>
<h4> concatenate (<i>othersound</i>)</h4>
Concatenates the sample data from <i>othersound</i> to the end of this sound.
The sounds must be of the same type, i.e., have the same sample rate, sample
encoding format, and number of channels. This command applies to in-memory
sounds only.
<h4> configure (<i>option=value</i> ...)</h4>
Sets the options for the sound. The possible options are listed <a
href="#soundoptions">above</a>. It is also possible to access the options
by treating the sound object as a dictionary, i.e., the following two expressions
are equivalent:
<blockquote>
<pre>mysound["byteorder"] = "littleEndian"<br>mysound.configure(byteorder="littleEndian")</pre>
</blockquote>
<b>configure</b> may be abbreviated as <b>config</b>.
<h4> convert (<i>option=value</i>)</h4>
Converts a sound to a different sample encoding, sample rate, or number
of channels. Options can be any of the following: -rate, -channels, or
-encoding.
<h4> copy (<i>othersound</i>)</h4>
Copies sample data from <i>othersound</i>. Optionally a range of samples
to copy can be specified using the <b>start</b> and <b>end</b> options. Any
active play operation is stopped before the command is executed if the format
of the new sound differs from the current. This command applies to in-memory
sounds only.
<h4> crop (<i>start=n, end=n</i>)</h4>
Crops the sound to the given range [start..end], i.e., all samples before
and after these limits will be removed. This command applies to in-memory
sounds only.
<h4> data (<i>variable</i>)</h4>
Loads sound data from a binary string. The same options apply as for the <i>read()</i> command.
<h4> destroy( )</h4>
Removes the Tcl command associated with this sound and frees its storage.
<h4> dBPowerSpectrum ( )</h4>
Computes the log FFT power spectrum of the sound (at the sample number given
in the <b>start</b> option) and returns a list of dB values. See the section
item for a description of the rest of the options. Optionally an ending point
can be given, using the <b>end</b> option. In this case the result is the
average of consecutive FFTs in the specified range. Their default spacing
is taken from the <b>fftlength</b> but this can be changed using the <b>skip</b>
option, which tells how many points to move the FFT window each step. Options:
<center>
<table border="1">
<tbody>
<tr>
<td><b>start</b></td>
<td><br>
</td>
</tr>
<tr>
<td><b>end</b></td>
<td><br>
</td>
</tr>
<tr>
<td><b>fftlength</b></td>
<td><br>
</td>
</tr>
<tr>
<td><b>windowlength</b></td>
<td><br>
</td>
</tr>
<tr>
<td><b>windowtype</b></td>
<td><br>
</td>
</tr>
<tr>
<td><b>skip</b></td>
<td><br>
</td>
</tr>
<tr>
<td><b>channel</b></td>
<td><br>
</td>
</tr>
<tr>
<td><b>preemphasisfactor</b></td>
<td><br>
</td>
</tr>
</tbody>
</table>
</center>
<h4> filter (<i>filter=filterobject</i>)</h4>
Applies the filter to the sound. This command applies to in-memory sounds
only.
<h4> flush ( )</h4>
Removes all audio data from the sound. This command applies to in-memory
sounds only.
<h4> info ( )</h4>
Returns a string with information about the sound. The elements of the string
are [<i>length, rate, max, min, encoding, channels, fileFormat, headerSize</i>
].
<h4> insert (<i>sound=othersound, position=sample</i> ...)</h4>
Inserts <i>othersound</i> at position <i>sample</i>. Optionally a range of
samples to copy can be specified, using the <b>start</b> and <b>end</b> options.
This command applies to in-memory sounds only.
<h4> length ( )</h4>
Gets the length of the sound. With an additional numeric argument, it will
set the length of the sound. The <b>unit</b> option specifies whether the
sound should be measured in "SAMPLES" (the default) or "SECONDS". If the
new length is larger than the current length, the sound is padded with additional
silence.
<h4> max ( )</h4>
Returns the largest positive sample value of the sound. A range of samples
to be examined can be specified with the <b>start</b> and <b>end</b> options.
The channel to be examined can be specified with the <b>channel</b> option.
The default is to check all channels and return the maximum value.
<h4> min ( )</h4>
Returns the largest negative sample value of the sound. A range of samples
to be examined can be specified with the <b>start</b> and <b>end</b> options.
The channel to be examined can be specified with the <b>channel</b> option.
The default is to check all channels and return the minimum value.
<h4> mix (<i>othersound</i>)</h4>
Mixes sample data from <i>othersound</i>. Optionally a range of samples,
where the mix operation will be applied, can be specified using the <b>start</b> and <b>end</b> options. The <b>mixscaling</b> option controls how much to scale <i>othersound</i> before mixing. The option <b>prescaling</b> controls how much to scale the original sound before mixing. This command applies to in-memory sounds only.
<h4> pause ( )</h4>
Pauses the current play/record operation. The next <i>pause()</i> invocation
resumes play/record. If there is a number of instances playing of a sound
object, all of them are paused.
<h4> pitch ( )</h4>
Returns a list of pitch values computed using the AMDF method. The values
are spaced 10 ms. A range of samples can be given using the <b>start</b> and
<b>end</b> options. If a frequency range of valid pitch values is known, this
can be specified using the <b>maxpitch</b> and <b>minpitch</b> options.
<h4> play ( )</h4>
Plays the sound. All options are ignored if <i>play()</i> is used to resume
a paused play options. If a <i>play()</i> command is issued while another
one is in progress, the latter one is queued up and starts to play as soon
as possible. The lag before this new sound is audible can be controlled using
the <i>audio.latency()</i> command.
<p>For in-memory sounds, a number of options are available. </p>
<center>
<table border="1">
<tbody>
<tr>
<td><b>start</b></td>
<td>specifies a start position in samples</td>
</tr>
<tr>
<td><b>end</b></td>
<td>specifies an end position in samples (-1 can be used to specify the end of the sound)</td>
</tr>
<tr>
<td><b>output</b></td>
<td>can specify any of the possible output ports returned by the <i>audio.outputs()</i>
command </td>
</tr>
<tr>
<td><b>blocking</b></td>
<td>specifies whether playback should be asynchronous or not, i.e., if it
is to be played in the background or it the <i>play()</i> command should return
only after the sound has been played. </td>
</tr>
<tr>
<td><b>command</b></td>
<td>specifies a command to be executed when the end of the sound is reached </td>
</tr>
<tr>
<td><b>device</b></td>
<td>selects which audio device to use</td>
</tr>
<tr>
<td><b>filter</b></td>
<td>specifies a filter which is to be applied during output </td>
</tr>
<tr>
<td><b>starttime</b></td>
<td>schedules the start of playback (in ms) relative to a previous play
operation</td>
</tr>
</tbody>
</table>
</center>
<h4> read (<i>filename</i>)</h4>
Reads new sound data from a file. Current supported file formats are WAV,
MP3, AU, SND, AIFF, SD, SMP, CSL, and RAW binary. The command returns the
file format detected. It is possible to force a file to be read as RAW using
by setting the option <b>fileformat=RAW</b>. In this case, properties of
the sound data can be specified by hand, using the <b>rate, channels, encoding,
skiphead, byteorder</b>, and <b>guessproperties</b> options, as described
<a href="#soundoptions">above</a>.
<h4> record ( )</h4>
Starts recording data from the audio device into the sound object. You may
use the <b>input</b> option to specify one of the available input ports (as
returned by the <i>audio.inputs()</i> command) and the <b>device</b> option
to select which audio input device to use.
<p>For in-memory sounds, the <b>append=1</b> option specifies that the new
audio data should be appended to the end of the existing sound instead of
replacing it. </p>
<p>For channel-based sounds, the <b>fileformat</b> option can be used to specify
the file format to be used when writing data, since there is no filename
to infer the format from. </p>
<h4> reverse ( )</h4>
Reverses the sound. A range of samples can be specified with the <b>start</b>
and <b>end</b> options. This command applies to in-memory sounds only.
<h4> sample (<i>sample</i>)</h4>
Gets the value of the specified sample number. Sets the value with an additional
numeric argument. When setting samples, one value should be specified for
each channel you want to change. Some examples of setting:
<blockquote>
<pre># Sets the 1000th sample to 0 (of a mono sound)<br>mysound.sample(1000, 0)<br><br># Sets both channels of a stero sound<br>mysound.sample(1000, 0, 0)<br><br># Sets only the left channel, leaves right channel unchanged<br>mysound.sample(1000, left=0)<br><br># Sets only the right channel, leaves left channel unchaged<br>mysound.sample(1000, right=0)</pre>
</blockquote>
<h4> stop ( )</h4>
Stops the current play or record operation. If there is a queue of sounds
to play, each of them can stop playback using <i>stop()</i>. If a callback
was registered using the <i>command</i> option to <i>play()</i>, it is not
executed.
<h4> write (<i>filename</i>)</h4>
Writes sound data to a file. A range of samples to save can be specified
using the <b>start</b> and <b>end</b> options. The file format is guessed
from the filename extension, but the guess can be overridden with the <b>
fileformat</b> option. If you specify RAW file format, the sound will be
saved to file without a header and using the natural byte order of the machine
(overrideable with the <b>byteorder</b> option).
<h2> The audio object</h2>
The <tt>audio</tt> object gives access to various properties of the available
audio devices. It is created automatically by <i>initializeSnack</i>.
<h3> Methods</h3>
<h4> elapsedTime ( )</h4>
Returns the time elapsed since the start of the last playback operation.
<h4> encodings ( )</h4>
Returns a list of supported sample encoding formats for the currently selected device.
<h4> rates ( )</h4>
Returns a list of supported sample rates for the currently selected device.
<h4> inputDevices ( )</h4>
Returns a list of available audio input devices.
<h4> playLatency ( )</h4>
Sets/queries (in ms) how much sound will be queued up at any time to the
audio device for playback. A low value makes new sound reach the loudspeakers
quickly at the risk of gaps in the output stream. An appropriate value should
be chosen with regard to processor speed and load.
<h4> pause ( )</h4>
Toggles between pause/play for all playback on the audio device.
<h4> play ( )</h4>
Resumes paused playback on the audio device.
<h4> play_gain ( )</h4>
Returns the current play gain value if invoked without a parameter. If an
integer value is given, play gain is set to the given value. Valid values
are in the range 0 to 100.
<h4> outputDevices ( )</h4>
Returns a list of available audio output devices.
<h4> record_gain ( )</h4>
Returns the current record gain value if invoked without a parameter. If
an integer value is given, record gain is set to the given value. Valid values
are in the range 0 to 100.
<h4> selectOutput (<i>device</i>)</h4>
Selects an audio output device to be used as default.
<h4> selectInput (<i>device</i>)</h4>
Selects an audio input device to be used as default.
<h4> stop ( )</h4>
Stops all playback on the audio device.
<h2> The mixer object</h2>
The <tt>mixer</tt> object gives access to various properties of mixer devices,
such as input/output jack, supported ports, mixer lines, and gain. It is created
automatically by <i>initializeSnack</i>.
<h3> Methods</h3>
<h4> channels (<i>line</i>)</h4>
Returns a list with the names of the channels for the specified <i>line</i>
.
<h4> devices ( )</h4>
Returns a list of available mixer devices.
<h4> input ( )</h4>
Gets/sets the current input jack. You can optionally give a boolean Tcl variable
as an argument.
<h4> inputs ( )</h4>
Returns a list of available input ports.
<h4> lines ( )</h4>
Returns a list with the names of the lines of the mixer device.
<h4> output ( )</h4>
Gets/sets the current output jack. You can optionally give a boolean Tcl
variable as an argument.
<h4> outputs ( )</h4>
Returns a list of available output ports.
<h4> update ( )</h4>
Updates all linked variables to reflect the status of the mixer device.
<h4> volume (<i>line</i>)</h4>
Return the current volume setting for <i>mixer</i>. You can optionally link
a Tcl variable to the value by including it as an argument. If you link two
Tcl variables, they are used for the left and right channels respectively.
<h4> select (<i>device</i>)</h4>
Selects a mixer device to be used as the default.
<h2> The Filter class</h2>
Filter objects can interact with sound objects either during playback or
by using the <i>filter()</i> command of the sound object.
<p>Filters in Snack are still in an early stage of development. Consult the
Snack documentation for further details. </p>
<h2> The SnackCanvas class</h2>
SnackCanvas is a subclass of Tkinter.Canvas that has three additional kinds
of canvas items: waveforms, spectrograms, and sections (power spectra).
<h3> Waveforms</h3>
Draw waveform items on the canvas using the <b>create_waveform</b> method.
Obligatory arguments are the <b>x</b> and <b>y</b> coordinates of the waveform's
top-right corner. Options are:
<table border="1">
<tbody>
<tr>
<td><b>anchor</b></td>
<td>works as for ordinary Tk canvas items</td>
</tr>
<tr>
<td><b>channel</b></td>
<td>selects which channel to show for multi-channel sounds. Use "left",
"right", "both", "all", -1 (all), or a channel number counting from 0 (left).</td>
</tr>
<tr>
<td><b>end</b></td>
<td>select the end-point of the time-range to draw</td>
</tr>
<tr>
<td><b>fill</b></td>
<td>works as for ordinary Tk canvas items</td>
</tr>
<tr>
<td><b>frame</b></td>
<td>boolean value controlling whether a frame will be drawn</td>
</tr>
<tr>
<td><b>height</b></td>
<td>the height of the waveform</td>
</tr>
<tr>
<td><b>limit</b></td>
<td>specifies the maximum shown value for the sound amplitude</td>
</tr>
<tr>
<td><b>pixelspersecond</b></td>
<td>determines the scaling factor in the x direction, which also gives the
width. If both <b>width</b> and <b>pixelspersecond</b> are specified, the
waveform will be cut at one end depending on if a <b>start</b> or <b>end</b>
option was also given.</td>
</tr>
<tr>
<td><b>shapefile</b></td>
<td>specifies a file for storing/retrieving precomputed waveform shape information</td>
</tr>
<tr>
<td><b>sound</b></td>
<td>specifies which sound object to link to</td>
</tr>
<tr>
<td><b>start</b></td>
<td>selects the starting point of the time-range to draw</td>
</tr>
<tr>
<td><b>stipple</b></td>
<td>works as for ordinary Tk canvas items</td>
</tr>
<tr>
<td><b>subsample</b></td>
<td>useful for large sounds to specify how precisely they should be analyzed
for the shape calculation. The default value 1 uses every sample in the sound
to draw the waveform envelope, which can be slow for large sounds. A value
of 10 uses every tenth. Care should be used when specifying values. Using
large values may lead to incorrect envelope shapes.</td>
</tr>
<tr>
<td><b>tags</b></td>
<td>works as for ordinary Tk canvas items</td>
</tr>
<tr>
<td><b>width</b></td>
<td>width of the waveform. See the entry for <b>pixelspersecond</b> for
what happens if you specify both options.</td>
</tr>
<tr>
<td><b>zerolevel</b></td>
<td>specifies whether a line will be drawn for the zero amplitude level.</td>
</tr>
</tbody>
</table>
<h3> Spectrograms</h3>
Draw a spectrogram of a sound on the canvas with the <b>create_spectrogram</b>
method. Obligatory arguments are the <b>x</b> and <b>y</b> positions of the
top-right corner of the spectrogram. Options are:
<table border="1">
<tbody>
<tr>
<td><b>anchor</b></td>
<td>works as for ordinary Tk canvas items</td>
</tr>
<tr>
<td><b>brightness</b></td>
<td>takes a value between -100.0 and 100.0</td>
</tr>
<tr>
<td><b>channel</b></td>
<td>selects which channel to show for multi-channel sounds. Use "left",
"right", "both", "all", -1 (all), or a channel number counting from 0 (left).</td>
</tr>
<tr>
<td><b>colormap</b></td>
<td>takes a list of colours as parameter. At least two must be specified.
The first colour is used for the lowest intensity in the spectrogram. An empty
list ives the default 32-level grey scale.</td>
</tr>
<tr>
<td><b>contrast</b></td>
<td>takes a value between -100.0 and 100.0</td>
</tr>
<tr>
<td><b>end</b></td>
<td>gives the end-point of the time-range to be drawn.</td>
</tr>
<tr>
<td><b>fftlength</b></td>
<td>specifies the number of FFT points (8, 16, 32, 64, 128, 256, 512, 1024,
2048, 4096).</td>
</tr>
<tr>
<td><b>gridcolor</b></td>
<td>specifies the colour of the grid.</td>
</tr>
<tr>
<td><b>gridfspacing</b></td>
<td>the spacing between frequency markers on the y-axis in Hertz. The default
value of 0 means no grid.</td>
</tr>
<tr>
<td><b>gridtspacing</b></td>
<td>the spacing between the time markers on the x-axis in seconds. The default
value of 0 means no grid.</td>
</tr>
<tr>
<td><b>height</b></td>
<td>height of the spectrogram.</td>
</tr>
<tr>
<td><b>pixelspersecond</b></td>
<td>determines the scaling factor in the x direction, which also gives the
width. If both <b>width</b> and <b>pixelspersecond</b> are specified, the
spectrogram will be cut at one end depending on if a <b>start</b> or <b>end</b>
option was also given.</td>
</tr>
<tr>
<td><b>preemphasisfactor</b></td>
<td>specifies the amount of preemphasis to be applied to the signal prior
to the FFT analysis.</td>
</tr>
<tr>
<td><b>sound</b></td>
<td>specifies which sound to link to.</td>
</tr>
<tr>
<td><b>start</b></td>
<td>the starting-point of the time-range to be drawn.</td>
</tr>
<tr>
<td><b>tags</b></td>
<td>works as for ordinary Tk canvas items.</td>
</tr>
<tr>
<td><b>topfrequency</b></td>
<td>the frequency value at the top of the spectrogram.</td>
</tr>
<tr>
<td><b>width</b></td>
<td>width of the spectrogram. See the entry for <b>pixelspersecond</b> for
what happens if you specify both options.</td>
</tr>
<tr>
<td><b>windowtype</b></td>
<td>"hanning", "hamming", "bartlett", "blackman", or "rectangle"</td>
</tr>
<tr>
<td><b>winlength</b></td>
<td>specifies the size of the hamming window, which should be equal to or
less than the number of FFT points.</td>
</tr>
</tbody>
</table>
<p>Currently spectrograms have a limit of 32767 pixels. </p>
<h3> Sections (power spectra)</h3>
Draw an FFT log power spectrum section of a sound on a canvas with the <b>
create_section</b> method. Obligatory arguments are the <b>x</b> and <b>y</b>
coordinates of the top-right corner of the section. Options are:
<table border="1">
<tbody>
<tr>
<td><b>anchor</b></td>
<td>works as for ordinary Tk canvas items</td>
</tr>
<tr>
<td><b>channel</b></td>
<td>selects which channel to show for multi-channel sounds. Use "left",
"right", "both", "all", -1 (all), or a channel number counting from 0 (left).</td>
</tr>
<tr>
<td><b>end</b></td>
<td>gives the end-point of the time-range to be drawn.</td>
</tr>
<tr>
<td><b>fftlength</b></td>
<td>specifies the number of FFT points (8, 16, 32, 64, 128, 256, 512, 1024,
2048, 4096).</td>
</tr>
<tr>
<td><b>fill</b></td>
<td>works as for ordinary Tk canvas items</td>
</tr>
<tr>
<td><b>frame</b></td>
<td>specifies whether a frame will be drawn</td>
</tr>
<tr>
<td><b>height</b></td>
<td>height of the spectrogram.</td>
</tr>
<tr>
<td><b>maxvalue</b></td>
<td>specifies the top of the range (in dB) which will be shown. The default
range is 0.0 to -80.0 dB.</td>
</tr>
<tr>
<td><b>minvalue</b></td>
<td>specifies the bottom of the range (in dB) which will be shown. The default
range is 0.0 to -80.0 dB.</td>
</tr>
<tr>
<td><b>preemphasisfactor</b></td>
<td>specifies the amount of preemphasis to be applied to the signal prior
to the FFT analysis.</td>
</tr>
<tr>
<td><b>skip</b></td>
<td><br>
</td>
</tr>
<tr>
<td><b>sound</b></td>
<td>specifies which sound to link to.</td>
</tr>
<tr>
<td><b>start</b></td>
<td>the starting-point of the time-range to be drawn.</td>
</tr>
<tr>
<td><b>stipple</b></td>
<td>works as for ordinary Tk canvas items</td>
</tr>
<tr>
<td><b>tags</b></td>
<td>works as for ordinary Tk canvas items.</td>
</tr>
<tr>
<td><b>topfrequency</b></td>
<td>the highest frequency value shown for the section.</td>
</tr>
<tr>
<td><b>width</b></td>
<td>width of the spectrogram. See the entry for <b>pixelspersecond</b> for
what happens if you specify both options.</td>
</tr>
<tr>
<td><b>windowtype</b></td>
<td>"Hamming", "Hanning", "Bartlett", "Blackman", or "Rectangle"</td>
</tr>
<tr>
<td><b>winlength</b></td>
<td>specifies the size of the hamming window, which should be equal to or
less than the number of FFT points.</td>
</tr>
</tbody>
</table>
<h3> Putting SnackCanvas items on regular Canvases</h3>
It's possible to draw these new canvas items onto any canvas in your program,
not just those that are instances of SnackCanvas. You might need to do this
if you're using elaborations or subclasses of Canvas that have been written
by other people, for example, if you want to draw a waveform on a ScrolledCanvas
from the Python Megawidget collection.
<p>To accomplish this, tkSnack provides module-level versions of <tt>create_waveform</tt>
, <tt>create_section</tt>, and <tt>create_spectrogram</tt>. Simply use the
non-Snack canvas as the first argument. Instead of: </p>
<blockquote>
<pre>NonSnackCanvas.create_waveform(sound=tada)</pre>
</blockquote>
use:
<blockquote>
<pre><font color="#cc0000">tkSnack.createWaveform(NonSnackCanvas, sound=tada)<br><br></font></pre>
</blockquote>
<font color="#cc0000">If you're using Pmw Scrolled Canvas, remember that
you're drawing onto the ScrolledCanvas's Canvas object. In that case, you'll
need to do:<br>
</font>
<blockquote>
<pre><font color="#cc0000">tkSnack.createWaveform(myScrolledCanvas._canvas, sound=tada)</font><br></pre>
</blockquote>
<p> </p>
<hr> <br>
<pre><font face="Arial, Helvetica"><font color="#ff6600"><font size="-1">Last updated </font></font></font><!--#config timefmt="%B %d, %Y" --><!--#flastmod file="python-man.html"-->
</pre>
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