| 1 | /****************************************************************************
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| 2 | **
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| 3 | ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
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| 4 | ** All rights reserved.
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| 5 | ** Contact: Nokia Corporation ([email protected])
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| 6 | **
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| 7 | ** This file is part of the documentation of the Qt Toolkit.
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| 8 | **
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| 9 | ** $QT_BEGIN_LICENSE:FDL$
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| 10 | ** Commercial Usage
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| 11 | ** Licensees holding valid Qt Commercial licenses may use this file in
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| 12 | ** accordance with the Qt Commercial License Agreement provided with the
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| 13 | ** Software or, alternatively, in accordance with the terms contained in a
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| 14 | ** written agreement between you and Nokia.
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| 15 | **
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| 16 | ** GNU Free Documentation License
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| 17 | ** Alternatively, this file may be used under the terms of the GNU Free
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| 18 | ** Documentation License version 1.3 as published by the Free Software
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| 19 | ** Foundation and appearing in the file included in the packaging of this
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| 20 | ** file.
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| 21 | **
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| 22 | ** If you have questions regarding the use of this file, please contact
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| 23 | ** Nokia at [email protected].
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| 24 | ** $QT_END_LICENSE$
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| 25 | **
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| 26 | ****************************************************************************/
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| 27 |
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| 28 | /*!
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| 29 | \example demos/spectrum
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| 30 | \title Spectrum Analyzer
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| 31 |
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| 32 | The Spectrum Analyzer demo shows how the \l{QtMultimedia Module} can be
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| 33 | used in Qt applications to capture and then play back an audio stream.
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| 34 |
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| 35 | \image spectrum-demo.png
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| 36 |
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| 37 | Because QtMultimedia allows the application to access the raw audio
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| 38 | stream, the data can either be inspected or modified by the application.
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| 39 | The Spectrum Analyzer demo displays three pieces of information while
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| 40 | audio is being either captured or played back:
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| 41 |
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| 42 | \list
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| 43 | \o Information about the raw audio stream, shown in the uppermost widget:
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| 44 | \list
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| 45 | \o The amount of data currently in the buffer, shown in blue
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| 46 | \o The segment of data which was most recently analysed to compute
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| 47 | the frequency spectrum, shown in green
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| 48 | \o The raw audio waveform, shown in white and scrolling from right to
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| 49 | left
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| 50 | \endlist
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| 51 | \o A representation of the frequency spectrum, shown at the lower left
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| 52 | \o The current RMS level of the audio stream, and the recent 'high
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| 53 | watermark' level, shown at the lower right
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| 54 | \endlist
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| 55 |
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| 56 | Spectrum analysis is performed by calculating the Fast Fourier Transform
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| 57 | (FFT) of a segment of audio data. An open-source library,
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| 58 | \l{http://ldesoras.free.fr/prod.html}{FFTReal}, against which the
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| 59 | application is dynamically linked, is used to compute the transform.
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| 60 | */
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| 61 |
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