audio.h File Reference

Audio library. More...

#include <sys/event_queue.h>

Go to the source code of this file.

Data Structures
struct	_audio_port_param
	Audio port parameter data structure. More...
struct	_audio_port_config
	Audio port config data structure. More...

Macros
#define	AUDIO_BLOCK_SAMPLES   256
	Number of samples in an audio block.
#define	AUDIO_STATUS_READY   1
	Audio port is ready to play.
#define	AUDIO_STATUS_RUN   2
	Audio port is playing.
#define	AUDIO_STATUS_CLOSE   0x1010
	Audio port has been closed.
#define	AUDIO_PORT_2CH   2
	2-channel (stereo) output.
#define	AUDIO_PORT_8CH   8
	8-channel output.
#define	AUDIO_PORT_INITLEVEL   0x1000
	Set initial output level.
#define	AUDIO_BLOCK_8   8
	8 blocks are allocated in the audio buffer
#define	AUDIO_BLOCK_16   16
	16 blocks are allocated in the audio buffer
#define	AUDIO_BLOCK_32   32
	32 blocks are allocated in the audio buffer

Typedefs
typedef struct _audio_port_param	audioPortParam
	Audio port parameter data structure.
typedef struct _audio_port_config	audioPortConfig
	Audio port config data structure.

Functions
s32	audioInit ()
	Initialize audio subsystem. More...
s32	audioQuit ()
	Initialize audio subsystem. More...
s32	audioPortOpen (audioPortParam *param, u32 *portNum)
	Open audio port. More...
s32	audioPortStart (u32 portNum)
	Start playing on audio port. More...
s32	audioPortStop (u32 portNum)
	Stop playing on audio port. More...
s32	audioGetPortConfig (u32 portNum, audioPortConfig *config)
	Get config of opened audio port. More...
s32	audioPortClose (u32 portNum)
	Close an opened audio port. More...
s32	audioCreateNotifyEventQueue (sys_event_queue_t *eventQ, sys_ipc_key_t *queueKey)
	Create a notify event queue for audio events. More...
s32	audioSetNotifyEventQueue (sys_ipc_key_t queueKey)
	Set the current event queue for audio events. More...
s32	audioRemoveNotifyEventQueue (sys_ipc_key_t queueKey)
	Disconnect the current event queue from the audio subsystem. More...

Detailed Description

Audio library.

This library manages communications of the application with the system audio server. It basically allows the application to play raw PCM audio by filling a circular buffer.

To play audio, follow these steps:

• Initialize the audio system for the application (audioInit).
• Open an audio port with audioPortOpen, which returns a unique port number.
• Allocate a audioPortConfig object with audioGetPortConfig.
• Create a notify event queue (audioCreateNotifyEventQueue).
• Set the created event queue as the current event queue (audioSetNotifyEventQueue).
• Eventually drain the existing events in the queue (sysEventQueueDrain).
• Start the audio port (audioPortStart).
• As soon as you receive an event from the notify event queue (sysEventQueueReceive), you can write the next block into the buffer. The first block number is 0, the following is 1, and so on until you reach the number of allocated blocks (specified in the audioPortParam::numBlocks value you provide when you call audioPortOpen), then the block number returns to 0. The address of block 0 is the audioDataStart field of the audioPortConfig structure. Then the address of block x is audioDataStart + x * numChannels * AUDIO_BLOCK_SAMPLES * sizeof(float). The size of each block in bytes is numChannels * AUDIO_BLOCK_SAMPLES * sizeof(float).

To stop playing audio, the steps are:

• Stop the audio port (audioPortStop).
• Unset the current event queue (audioRemoveNotifyEventQueue).
• Close the audio port (audioPortClose).
• Destroy the event queue (sysEventQueueDestroy).
• Quit the audio system (audioQuit).

The PCM audio sample format is 32-bit floating point where sample values vary from -1 to 1. Samples are interlaced: for instance in stereo mode, even sample positions correspond to the left channel, and odd ones correspond to the right channel.

Function Documentation

audioCreateNotifyEventQueue()

s32 audioCreateNotifyEventQueue	(	sys_event_queue_t *	eventQ,
		sys_ipc_key_t *	queueKey
	)

Create a notify event queue for audio events.

Parameters

eventQ	Pointer to the event queue object to be updated.
queueKey	Pointer to storage for the returned queue key.

Returns

zero if no error, nonzero otherwise.

audioGetPortConfig()

s32 audioGetPortConfig	(	u32	portNum,
		audioPortConfig *	config
	)

Get config of opened audio port.

Parameters

portNum	Port id as returned by audioPortOpen.
config	Pointer to the port config structure to be updated.

Returns

zero if no error, nonzero otherwise.

audioInit()

s32 audioInit

(

)

Initialize audio subsystem.

Returns

zero if no error, nonzero otherwise.

audioPortClose()

s32 audioPortClose

(

u32

portNum

)

Close an opened audio port.

Parameters

portNum

Port id as returned by audioPortOpen.

Returns

zero if no error, nonzero otherwise.

audioPortOpen()

s32 audioPortOpen	(	audioPortParam *	param,
		u32 *	portNum
	)

Open audio port.

Parameters

param	Pointer to and audio port parameter data structure.
portNum	Pointer to storage for the returned port id.

Returns

zero if no error, nonzero otherwise.

audioPortStart()

s32 audioPortStart

(

u32

portNum

)

Start playing on audio port.

Parameters

portNum

Port id as returned by audioPortOpen.

Returns

zero if no error, nonzero otherwise.

audioPortStop()

s32 audioPortStop

(

u32

portNum

)

Stop playing on audio port.

Parameters

portNum

Port id as returned by audioPortOpen.

Returns

zero if no error, nonzero otherwise.

audioQuit()

s32 audioQuit

(

)

Initialize audio subsystem.

Returns

zero if no error, nonzero otherwise.

audioRemoveNotifyEventQueue()

s32 audioRemoveNotifyEventQueue

(

sys_ipc_key_t

queueKey

)

Disconnect the current event queue from the audio subsystem.

Parameters

queueKey

The queue key value (must have been created using audioCreateNotifyEventQueue).

Returns

zero if no error, nonzero otherwise.

audioSetNotifyEventQueue()

s32 audioSetNotifyEventQueue

(

sys_ipc_key_t

queueKey

)

Set the current event queue for audio events.

Parameters

queueKey

The queue key value (musthave been created using audioCreateNotifyEventQueue).

Returns

zero if no error, nonzero otherwise.