[Libvisual-devel] VisAudio overhaul proposal.

[Dennis S. <sy...@yo...>]

Heya everyone.

I wrote the first version of the new VisAudio API proposal.

It's going to be a complete overhaul, and thus should be done right.

PLEASE read this document, and comment upon it! Please confirm if it's
good or not. there are some open questions, discuss these. I want to
set this in stone, so we can start on it :)

Cheers,
Dennis

The document:
====================================================================================

This document describes the initial VisAudio overhaul design.

Version 0.1

Dennis Smit <sy...@yo...>
Libvisual project leader

_____________________________________________________________________________________

Goals:
	Ability to mix channels.
	Audio energy registration, calculation (already done).
	normalized spectrum (logified).
	Internally, use floats to represent audio. (from 0.0 to 1.0 or -1.0 to
1.0 ?)
	Use floats to represent the spectrum (from 0.0 to 1.0)
	Have conversion code to go from short audio to float.
	Basic conversion for the frequency (hz) of the input.
	BPM detection:

http://www.gamedev.net/reference/programming/features/beatdetection/page2.asp

		Provide 6 vars to directly detect hits on the six bands.

Open questions:
	How do we want to do the number of samples ? (aka the length of the
buffer)
	How to handle multiple channels, channel mixing, how to handle 5.1,
7.1, 9.1 etc ?

Internal audio representation:
	In floats.
	Fixed frequency ? (I personally prefer this)
	How large do we want our buffers ?


API:
enum {
	VISUAL_AUDIO_FROM_SIGNED_96000
	VISUAL_AUDIO_FROM_SIGNED_48000
	VISUAL_AUDIO_FROM_SIGNED_44100
	VISUAL_AUDIO_FROM_SIGNED_32000
	VISUAL_AUDIO_FROM_SIGNED_22500
	VISUAL_AUDIO_FROM_SIGNED_11250
	VISUAL_AUDIO_FROM_SIGNED_8000
	VISUAL_AUDIO_FROM_UNSIGNED_96000
	VISUAL_AUDIO_FROM_UNSIGNED_48000
	VISUAL_AUDIO_FROM_UNSIGNED_44100
	VISUAL_AUDIO_FROM_UNSIGNED_32000
	VISUAL_AUDIO_FROM_UNSIGNED_22500
	VISUAL_AUDIO_FROM_UNSIGNED_11250
	VISUAL_AUDIO_FROM_UNSIGNED_8000
} VisAudioSoundImportType;

VisAudio {
	VisObject		object;

	float			sound[3][2048];
	float			spectrum[3][256];
	float			spectrum_normalized[3][256]
	float			energy;

	VisFFTState	       *fft_state;

	VisAudioBeat	       *bpm;
};

VisAudioBeat {
	VisObject		object;

	...			history[1024][6];
	...			energy[6];

	int			bpm;
	int			beat;
	int			beat_channels[6];	// Set the specific channel on a beat
	int			active_channel;

	float			accuracy;
};

/* Prototypes */
VisAudio *visual_audio_new (void);
int visual_audio_analyze (VisAudio *audio);

int visual_audio_sound_import (VisAudio *audio, VisAudioSoundImportType
type, void *sound_buffer, int buffer_length);

VisAudioBeat *visual_audio_beat_new (void);
int visual_audio_beat_analyse (VisAudio *audio);