IRIX Audio Library (libirixaudio) Manual

Overview

The IRIX Audio Library is a lightweight, C-based audio I/O library designed for Silicon Graphics IRIX systems. It provides a simple, efficient interface for audio input, output, and device management, built on top of the IRIX Audio Library (AL).

Library Components

Key Features

• Support for audio input and output streams
• Multiple audio data formats
• Device discovery and information retrieval
• Low-level audio device abstraction

Supported Audio Formats

• 8-bit signed integer
• 16-bit signed integer
• 24-bit signed integer
• 32-bit signed integer
• 32-bit float
• 64-bit float

Data Structures

Audio Modes

typedef enum {
    IRIX_AUDIO_INPUT,    // Input-only mode
    IRIX_AUDIO_OUTPUT,   // Output-only mode
    IRIX_AUDIO_DUPLEX    // Simultaneous input and output
} IrixAudioMode;

Audio Formats

typedef enum {
    IRIX_AUDIO_SINT8 = 0x1,     // 8-bit signed integer
    IRIX_AUDIO_SINT16 = 0x2,    // 16-bit signed integer
    IRIX_AUDIO_SINT24 = 0x4,    // 24-bit signed integer
    IRIX_AUDIO_SINT32 = 0x8,    // 32-bit signed integer
    IRIX_AUDIO_FLOAT32 = 0x10,  // 32-bit float
    IRIX_AUDIO_FLOAT64 = 0x20   // 64-bit float
} IrixAudioFormat;

Device Information Structure

typedef struct {
    int max_output_channels;    // Maximum output channels
    int min_output_channels;    // Minimum output channels
    int max_input_channels;     // Maximum input channels
    int min_input_channels;     // Minimum input channels
    int* sample_rates;          // Supported sample rates
    int sample_rates_count;     // Number of supported sample rates
    unsigned int native_formats;// Supported audio formats
} IrixAudioDeviceInfo;

Stream Parameters

typedef struct {
    IrixAudioMode mode;     // Audio stream mode
    int channels;           // Number of audio channels
    int sample_rate;        // Sampling rate
    int buffer_size;        // Audio buffer size
} IrixAudioStreamParams;

Function Reference

Initialization and Device Management

int irix_audio_initialize()

• Discovers and initializes audio devices
• Returns number of devices found or -1 on error

int irix_audio_get_device_count()

• Retrieves the number of available audio devices

int irix_audio_get_device_info(int device_index, IrixAudioDeviceInfo* info)

• Retrieves detailed information about a specific audio device
• Fills the IrixAudioDeviceInfo structure
• Returns 0 on success, -1 on error

void irix_audio_cleanup()

• Frees resources allocated during device initialization
• Should be called at the end of audio operations

Stream Management

IrixAudioStream* irix_audio_open_stream(IrixAudioStreamParams* params)

• Creates and configures an audio stream
• Returns a pointer to the created stream or NULL on error

void irix_audio_close_stream(IrixAudioStream* stream)

• Closes an open audio stream
• Releases associated resources

Audio I/O Operations

int irix_audio_write_frames(IrixAudioStream* stream, void* buffer, int frames)

• Writes audio frames to an output stream
• Returns number of frames written or -1 on error

int irix_audio_read_frames(IrixAudioStream* stream, void* buffer, int frames)

• Reads audio frames from an input stream
• Returns number of frames read or -1 on error

Error Handling

const char* irix_audio_get_last_error()

• Retrieves the last error message
• Useful for diagnosing issues during audio operations

Usage Examples

Simple Audio Output

// Set up stream parameters
IrixAudioStreamParams params = {
    .mode = IRIX_AUDIO_OUTPUT,
    .channels = 2,
    .sample_rate = 44100,
    .buffer_size = 256
};

// Open stream
IrixAudioStream* stream = irix_audio_open_stream(&params);
if (!stream) {
    printf("Error opening stream: %s\n", irix_audio_get_last_error());
    return;
}

// Write audio data
float buffer[256];
// ... fill buffer with audio data ...
irix_audio_write_frames(stream, buffer, 256);

// Cleanup
irix_audio_close_stream(stream);

Audio Device Enumeration

// Initialize audio system
int device_count = irix_audio_initialize();
printf("Found %d audio devices\n", device_count);

// Print device information
for (int i = 0; i < device_count; i++) {
    IrixAudioDeviceInfo info;
    if (irix_audio_get_device_info(i, &info) == 0) {
        printf("Device %d: Input Channels %d, Output Channels %d\n",
               i, info.max_input_channels, info.max_output_channels);
    }
}

// Cleanup
irix_audio_cleanup();

Compilation and Linking

Compiler Flags

• Use -lirixaudio to link against the library
• Requires -lAL for IRIX Audio Library support
• Use -lm for math functions (e.g., sine wave generation)

Example Makefile Compilation

CC = cc
CFLAGS = -32 -mips3 -O2
LIBS = -lAL -lm -lirixaudio

my_audio_program: my_audio_program.c
    $(CC) $(CFLAGS) -o $@ $< $(LIBS)

Limitations and Considerations

• Specifically designed for IRIX 6.5 systems
• Depends on the IRIX Audio Library (AL)
• Limited to the audio capabilities of SGI hardware
• No built-in audio file format conversion

Version and Compatibility

• Extracted from RtAudio library
• Original Copyright (c) 2001-2005 Gary P. Scavone
• Converted from C++ to C for broader compatibility

Troubleshooting

• Always check irix_audio_get_last_error() after operations
• Ensure proper initialization and cleanup
• Verify device capabilities before opening streams
• Match buffer formats with device native formats

License

Refer to the original RtAudio library licensing terms

Contributing

Contributions and improvements are welcome. Please submit pull requests or issue reports to the project repository.