Copyright © 2011-2013 MultiMedia Soft How to use the Waveform Analyzer

After loading a sound the embedded Waveform Analyzer, implemented through the WaveformAnalyzer class, allows performing a detailed analysis of the sound itself with the purpose of generating a graphical representation of the sound's waveform.

 

The first step is to perform the sound's analysis through a call to the WaveformAnalyzer.AnalyzeFullSound method: the analysis can be more or less accurate depending upon the resolution set into the nResolution property of the WAVEFORM_ANALYZER_SETTINGS_2 class: higher resolutions will allow a better quality because more peaks will be detected: as a side effect, higher resolutions will require more memory and will generate larger bitmaps. When the results of an analysis are no more needed, the involved memory can be released through a call to the WaveformAnalyzer.FreeMemory method. The analysis can be aborted at any time through a call to the WaveformAnalyzer.AnalyzeAbort method.

 

After calling this method, the control will allow the container application to stay up-to-date about the analysis advancement through CallbackPercentage delegate set through the CallbackPercentageSet method.

 

After completing the waveform analysis, you can request the level, expressed in percentage, of the highest and of the lowest peaks available inside a certain range of the waveform through the WaveformAnalyzer.GetMinMaxPeakLevelsForRange method.

 

At this point it's possible creating a graphical representation of analyzed sounds in one of the following modes:

 

Mode 1: Visual editing

Mode 2: Creation of bitmaps in various graphic formats

Mode 3: Rendering on a graphic Device Context (HDC)

 

 

Mode 1: Visual editing

 

In order to start the visual editing of the sound's waveform, we need to create the Waveform Analyzer user interface through a call to the WaveformAnalyzer.Create method. By default the Waveform Analyzer user interface will appear as in the picture below where the top waveform represents the left channel of a stereo sound while the bottom waveform represents the right channel of a stereo sound (sounds in mono are rendered using one single waveform):

 

 

Once the waveform analysis has been performed, you can immediately display the full waveform on the visible area of the analyzer through a call to the WaveformAnalyzer.SetDisplayRange method by passing 0 and -1 respectively to the nBeginPosInMs and nEndPosInMs parameters.

 

As most Windows controls with an user interface, the Waveform Analyzer can be:

 

 

The graphical appearance of this control is fully customizable and you can modify colors used to render the various elements and hide/show all of the elements surrounding the waveform representation: for this purpose you can retrieve the current graphical settings calling the WaveformAnalyzer.GetGraphicalSettings2 method and then modify them calling the WaveformAnalyzer.SetGraphicalSettings2 method: both methods receive a reference to an object of the WAVEFORM_ANALYZER_SETTINGS_2 class.

 

The Waveform Analyzer allows selecting/deselecting portions of the displayed waveform in two different ways:

 

 

 

 

The Waveform Analyzer allows zooming the displayed waveform in two different ways:

 

 

 

Whenever a change occurs on the user interface, the container application is notified through one of the following delegates:

 

 

The Waveform Analyzer automatically manages two vertical lines, one for displaying the current position during a playback session and another one for displaying a selection point: the look of these two lines can be modified trough the colorWavePositionLine and the colorWavePlaybackLine members of the WAVEFORM_ANALYZER_SETTINGS_2 class.

 

You have the possibility to add further vertical custom lines through the WaveformAnalyzer.VerticalLineAdd and WaveformAnalyzer.VerticalLineAddWithName methods and to remove them at a later time through the WaveformAnalyzer.VerticalLineRemove method: each custom line is identified by a unique identifier; once added, you can move/retrieve the position of custom lines through the WaveformAnalyzer.VerticalLineSetPosition and the WaveformAnalyzer.VerticalLineGetPosition methods; as a further feature you can also hide/show custom lines through the WaveformAnalyzer.VerticalLineShow method.

 

Vertical custom lines can be manually moved through the mouse; this action will invoke the CallbackWaveformAnalyzerLineMoved delegate set through the CallbackWaveformAnalyzerLineMovedSet method.

 

During playback you can be notified that the position of a custom vertical line has been reached through the CallbackWaveformAnalyzerLineReached delegate set through the CallbackWaveformAnalyzerLineReachedSet method.

 

Custom vertical lines can be saved into a file for later usage through the WaveformAnalyzer.VerticalLinesSave method and retrieved at a later time through the WaveformAnalyzer.VerticalLinesLoad method.

 

In order to ease management of custom vertical lines through mouse interaction, you can catch the CallbackWaveformAnalyzerMouseNotif delegate, set through the CallbackWaveformAnalyzerMouseNotifSet method, which reports the exact position where the mouse was pressed on the waveform: accurate positioning is guaranteed also when the waveform is zoomed. Mouse interaction can be enabled/disabled through the WaveformAnalyzer.MouseSelectionEnable method. During a playback session the mouse interaction is automatically disabled and an eventual call to this method will be ignored.

 

Each graphical element composing the Waveform Analyzer visualization is referenced by a specific rectangle on the screen: coordinates and dimensions of this rectangle, expressed in pixels, can be obtained through the WaveformAnalyzer.GetRectangle method.

 

Each time the graphical rendering of the Waveform Analyzer is completed, the container application is informed through the CallbackWaveformAnalyzerPaintDone delegate set through the CallbackWaveformAnalyzerPaintDoneSet method: this delegate will pass as parameter the HWND of the Waveform Analyzer window, allowing to perform further custom graphic rendering on the Waveform Analyzer surface; for this purpose you can obtain the handle to the device context (HDC) of the Waveform Analyzer through the GetDC Windows API.

 

 

 

Mode 2: Creation of bitmaps in various graphic formats

 

After completing the waveform analysis started through the WaveformAnalyzer.AnalyzeFullSound method, it will be possible requesting to the control the creation of the waveform's bitmap through a call to the WaveformAnalyzer.BitmapViewSaveToFile and WaveformAnalyzer.BitmapViewSaveToMemory methods. Through the WaveformAnalyzer.GetAnalysisInfo method you can know the exact number of peaks detected inside the loaded sound and the exact duration in milliseconds of each peak. When generating the bitmap for the full sound's waveform, the reported number of peaks will be exactly equal to the width in pixels of the bitmap. In case you should create a view of a given sound's range, you could obtain the number of pixels needed to display the waveform's view through a call to the WaveformAnalyzer.BitmapViewGetWidth method.

 

The generated waveform's bitmap will be rendered using colors set into the colorWaveLine and colorWaveBackground properties of the WAVEFORM_ANALYZER_SETTINGS_2 class.

 

Below you can see five bitmaps generated using the same sound (whose duration is around 2.4 seconds length) but with five different resolutions (just for your information the song used for generating these bitmaps is available on this link); all these bitmaps have been created using the same height of 100 pixels:

 

 

 

As mentioned before, you can also generate a "view" of a defined portion of the loaded sound: on the bitmap below you can see the original song in its full length (with WAVEFORM_RES_MAXIMUM resolution)

 

 

and below you can see the view of the same song for the range between 500 and 1500 milliseconds

 

 

 

On the samples above we have used a very small song limited to 2.4 seconds: in case you should be in need of displaying the full waveform of a longer song on a space much smaller than the total number of required pixels, the WaveformAnalyzer.BitmapViewSaveToFile and WaveformAnalyzer.BitmapViewSaveToMemory methods will shrink the waveform in order to fit exactly inside the available space; in the example below you can see a 3 minutes song fitting inside a 455 pixels wide bitmap: the original full length bitmap, using the WAVEFORM_RES_MAXIMUM resolution, would require a width of 243,683 pixels.

 

 

VERY IMPORTANT: When using high resolutions and big sound files, keep count that the Windows operating system has limits on the size of bitmaps creation; this means that it would be better avoiding the creation of very large bitmaps: in this case it would be a better approach splitting the total song's bitmap into several smaller bitmaps, for example creating bitmaps whose width in pixels doesn't exceed the current screen width.

 

 

 

Mode 3: Rendering on a graphic Device Context (HDC)

 

After completing the waveform analysis, it will be possible requesting to the control to render the waveform directly inside a graphical device context using the WaveformAnalyzer.BitmapViewDrawToHdc method; this may be quite useful if you should need to perform real-time rendering of the waveform on the screen. Although this could be also used for creating a scrolling waveform during playback, we suggest checking the How to scroll the sound's waveform during playback tutorial for further details about managing a scrolling waveform.