Aegisub/aegisub/src/audio_renderer_spectrum.h

// Copyright (c) 2005, 2006, Rodrigo Braz Monteiro
// Copyright (c) 2006, 2007, Niels Martin Hansen
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// $Id$

/// @file audio_renderer_spectrum.h
/// @see audio_renderer_spectrum.cpp
/// @ingroup audio_ui
///
/// Calculate and render a frequency-power spectrum for PCM audio data.

#ifndef AGI_PRE
#include <stdint.h>
#endif

class AudioProvider;

// Specified and implemented in cpp file, interface is private to spectrum code
class AudioSpectrumCacheManager;


/// @class AudioSpectrum
/// @brief Render frequency-power spectrum graphs for audio data.
///
/// Renders frequency-power spectrum graphs of PCM audio data using a fast fourier transform
/// to derive the data. The frequency-power data are cached to avoid re-computing them
/// frequently, and the cache size is limited by a configuration setting.
///
/// The spectrum image is rendered to a 32 bit RGB bitmap. Power data is scaled linearly
/// and not logarithmically, since the rendering is done with limited precision, but
/// an amplification factor can be specified to see different ranges.
class AudioSpectrum {
private:

	/// Internal cache management for the spectrum
	AudioSpectrumCacheManager *cache;

	/// Colour table used for regular rendering
	unsigned char colours_normal[256*3];

	/// Colour table used for rendering the audio selection
	unsigned char colours_selected[256*3];

	/// The audio provider to use as source
	AudioProvider *provider;

	unsigned long line_length; ///< Number of frequency components per line (half of number of samples)
	unsigned long num_lines;   ///< Number of lines needed for the audio
	unsigned int fft_overlaps; ///< Number of overlaps used in FFT
	float power_scale;         ///< Amplification of displayed power
	int minband;               ///< Smallest frequency band displayed
	int maxband;               ///< Largest frequency band displayed

public:
	/// @brief Constructor
	/// @param _provider Audio provider to render spectrum data for.
	///
	/// Reads configuration data for the spectrum display and initialises itself following that.
	AudioSpectrum(AudioProvider *_provider);
	/// @brief Destructor
	~AudioSpectrum();

	/// @brief Render a range of audio spectrum to a bitmap buffer.
	/// @param range_start First audio sample in the range to render.
	/// @param range_end   Last audio sample in the range to render.
	/// @param selected    Use the alternate colour palette?
	/// @param img         Pointer to 32 bit RGBX data
	/// @param imgleft     Offset from left edge of bitmap to render to, in pixels
	/// @param imgwidth    Width of bitmap to render, in pixels
	/// @param imgpitch    Offset from one scanline to the next in the bitmap, in bytes
	/// @param imgheight   Number of lines in the bitmap
	void RenderRange(int64_t range_start, int64_t range_end, bool selected, unsigned char *img, int imgleft, int imgwidth, int imgpitch, int imgheight);

	/// @brief Set the amplification to use when rendering.
	/// @param _power_scale Amplification factor to use.
	void SetScaling(float _power_scale);
};