The audio decoder interface for the libmsx audio replayer.

#include <audio_dec.h> More...

Collaboration diagram for The audio decoder interface for the libmsx audio replayer.:

Data Structures
struct	AudioDecoder
	The audio decoder interface. More...

Typedefs
typedef struct AudioDecoder	AudioDecoder
	The audio decoder interface.

Detailed Description

#include <audio_dec.h>

The audio decoder interface for the libmsx audio replayer.

The libmsx audio replayer can handle two dedicated audio decoders:

• one is a background music decoder,
• and the other is a sound effect decoder.

Each of the above audio decoders must implement the audio decoder interface of type AudioDecoder.

A music data loader or audio decoder implementation for the libmsx audio replayer must provide either or both of the follwing decoder specific APIs:

• An API used to set the background music (BGM) to the decoder. This API also attaches the BGM decoder to the replayer by calling audio_cb_bgm_changed().
• An API used to set the sound effects (SFX) to the decoder. This API also attaches the SFX decoder to the replayer by calling audio_cb_sfx_changed().

And it can also proivide some APIs such as:

• Looking up / load a music data from the storage,
• Get meta-data of a music (ex. default frequency, title, etc.),
• Turn auto-repeat feature on/off,
• and so on.

See also

Callback functions of the libmsx audio replayer.

Unified sound-chip buffer of the libmsx audio replayer.

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Data Structure Documentation

AudioDecoder

struct AudioDecoder

The audio decoder interface.

This object is used by libmsx audio replayer to decode music data.

The libmsx audio replayer can handle two dedicated audio decoders:

• one is a background music decoder,
• and the other is a sound effect decoder.

Decode music data then Store in the buffer

The decoder decodes the music data each time it is called and stores it in libmsx audio replayer's internal FIFO buffer by calling audio_buf_put().

To do this, each of the above audio decoders must implement the audio decoder interface of type AudioDecoder.

Attach the decoder to the libmsx audio replayer

The decoder must be attached to the replayer when a music data is changed or set to the decoder by the decoder specific API.

A decoder for background music (BGM) shall be attached to the replayer by audio_cb_bgm_changed(). So the audio_cb_bgm_changed() should be called when the BGM is changed or set to the decoder by the decoder specific API.

A decoder for sound effects (SFX) shall be attached to the replayer by audio_cb_sfx_changed(). So the audio_cb_sfx_changed() should be called when the SFX is changed or set to the decoder by the decoder specific API.

See also

Unified sound-chip buffer of the libmsx audio replayer.

Callback functions of the libmsx audio replayer.

Definition at line 89 of file audio_dec.h.

Data Fields
bool(*)(void)	decode_update	Function pointer to the decoder I/F decode_update(). This function is called by audio_play() several times (depending on the frequency of the replayer and VSYNC) if the decoder has been attached to the replayer. This function shall decodes the next sampled value of the music data. Then, by calling the function audio_buf_put(), the decoded value can be stored in the internal FIFO buffer of the libmsx audio replayer. (Or, it is done from the function decode_final().) If a music data has been set to the decoder and it is not reached to the end of music, this shall return true. If no music data is set to the decoder or the music is already finished, this shall return false. Returns true if the music has not ended. Postcondition The FIFO buffer of the libmsx audio replayer may or may not be updated. See also Unified sound-chip buffer of the libmsx audio replayer. audio_buf_put()
void(*)(void)	decode_final	Function pointer to the decoder I/F decode_final(). This function is called by audio_play() after several iterations of decode_update() if the decoder has been attached to the replayer. If decode_update() simply decodes but does not store in the libmsx audio replayer's internal FIFO buffer, the value decoded by decode_update() should be stored by this function in the FIFO buffer. Postcondition The FIFO buffer of the libmsx audio replayer shall be updated / finalized. See also Unified sound-chip buffer of the libmsx audio replayer. audio_buf_put()
void(*)(bool repeat)	set_repeat	Function pointer to the decoder I/F set_repeat(). Turn on/off the auto-repeat of the music. This function is called by audio_set_repeat() or when the decoder is attached to replayer. If the decoder does not support the auto-repeat function, the function pointer set_repeat may be set to NULL. Parameters repeat true: turn on, false: turn off

Typedef Documentation

AudioDecoder

typedef struct AudioDecoder AudioDecoder

The audio decoder interface.

This object is used by libmsx audio replayer to decode music data.

The libmsx audio replayer can handle two dedicated audio decoders:

• one is a background music decoder,
• and the other is a sound effect decoder.

Decode music data then Store in the buffer

The decoder decodes the music data each time it is called and stores it in libmsx audio replayer's internal FIFO buffer by calling audio_buf_put().

To do this, each of the above audio decoders must implement the audio decoder interface of type AudioDecoder.

Attach the decoder to the libmsx audio replayer

The decoder must be attached to the replayer when a music data is changed or set to the decoder by the decoder specific API.

A decoder for background music (BGM) shall be attached to the replayer by audio_cb_bgm_changed(). So the audio_cb_bgm_changed() should be called when the BGM is changed or set to the decoder by the decoder specific API.

A decoder for sound effects (SFX) shall be attached to the replayer by audio_cb_sfx_changed(). So the audio_cb_sfx_changed() should be called when the SFX is changed or set to the decoder by the decoder specific API.

See also

Unified sound-chip buffer of the libmsx audio replayer.

Callback functions of the libmsx audio replayer.