diff options
Diffstat (limited to 'src/output/sdl.c')
| -rw-r--r-- | src/output/sdl.c | 206 |
1 files changed, 206 insertions, 0 deletions
diff --git a/src/output/sdl.c b/src/output/sdl.c new file mode 100644 index 0000000..cc65021 --- /dev/null +++ b/src/output/sdl.c @@ -0,0 +1,206 @@ +/* + sdl: audio output via SDL cross-platform API + + copyright 2006-9 by the mpg123 project - free software under the terms of the LGPL 2.1 + see COPYING and AUTHORS files in distribution or http://mpg123.org + initially written by Nicholas J. Humfrey +*/ + +#include <math.h> + +#include <SDL.h> + +#include "audio.h" +#include "mpg123app.h" +#ifdef WIN32 +#include <windows.h> +#endif + +/* Including the sfifo code locally, to avoid module linkage issues. */ +#define SFIFO_STATIC +#include "sfifo.c" + +#include "debug.h" + + +#define SAMPLE_SIZE (2) +#define FRAMES_PER_BUFFER (256) +#define FIFO_DURATION (0.5f) + + + + +/* The audio function callback takes the following parameters: + stream: A pointer to the audio buffer to be filled + len: The length (in bytes) of the audio buffer +*/ +static void audio_callback_sdl(void *udata, Uint8 *stream, int len) +{ + audio_output_t *ao = (audio_output_t*)udata; + sfifo_t *fifo = (sfifo_t*)ao->userptr; + int bytes_read; + + /* Only play if we have data left */ + if ( sfifo_used( fifo ) < len ) { + warning("Didn't have any audio data for SDL (buffer underflow)"); + SDL_PauseAudio(1); + return; + } + + /* Read audio from FIFO to SDL's buffer */ + bytes_read = sfifo_read( fifo, stream, len ); + + if (len!=bytes_read) + warning2("Error reading from the FIFO (wanted=%u, bytes_read=%u).\n", len, bytes_read); + +} + +static int open_sdl(audio_output_t *ao) +{ + sfifo_t *fifo = (sfifo_t*)ao->userptr; + + /* Open an audio I/O stream. */ + if (ao->rate > 0 && ao->channels >0 ) { + size_t ringbuffer_len; + SDL_AudioSpec wanted; + + /* L16 uncompressed audio data, using 16-bit signed representation in twos + complement notation - system endian-ness. */ + wanted.format = AUDIO_S16SYS; + wanted.samples = 1024; /* Good low-latency value for callback */ + wanted.callback = audio_callback_sdl; + wanted.userdata = ao; + wanted.channels = ao->channels; + wanted.freq = ao->rate; + + /* Open the audio device, forcing the desired format */ + if ( SDL_OpenAudio(&wanted, NULL) ) { + error1("Couldn't open SDL audio: %s\n", SDL_GetError()); + return -1; + } + + /* Initialise FIFO */ + ringbuffer_len = ao->rate * FIFO_DURATION * SAMPLE_SIZE *ao->channels; + debug2( "Allocating %d byte ring-buffer (%f seconds)", (int)ringbuffer_len, (float)FIFO_DURATION); + if (sfifo_init( fifo, ringbuffer_len )) error1( "Failed to initialise FIFO of size %d bytes", (int)ringbuffer_len ); + } + + return(0); +} + + +static int get_formats_sdl(audio_output_t *ao) +{ + /* Only implemented Signed 16-bit audio for now */ + return MPG123_ENC_SIGNED_16; +} + + +static int write_sdl(audio_output_t *ao, unsigned char *buf, int len) +{ + sfifo_t *fifo = (sfifo_t*)ao->userptr; + + /* Sleep for half the length of the FIFO */ + while (sfifo_space( fifo ) < len ) +#ifdef WIN32 + Sleep( (FIFO_DURATION/2) * 1000); +#else + usleep( (FIFO_DURATION/2) * 1000000 ); +#endif + + /* Bung decoded audio into the FIFO + SDL Audio locking probably isn't actually needed + as SFIFO claims to be thread safe... + */ + SDL_LockAudio(); + sfifo_write( fifo, buf, len); + SDL_UnlockAudio(); + + + /* Unpause once the buffer is 50% full */ + if (sfifo_used(fifo) > (sfifo_size(fifo)*0.5) ) SDL_PauseAudio(0); + + return len; +} + +static int close_sdl(audio_output_t *ao) +{ + sfifo_t *fifo = (sfifo_t*)ao->userptr; + + SDL_CloseAudio(); + + /* Free up the memory used by the FIFO */ + sfifo_close( fifo ); + + return 0; +} + +static void flush_sdl(audio_output_t *ao) +{ + sfifo_t *fifo = (sfifo_t*)ao->userptr; + + SDL_PauseAudio(1); + + sfifo_flush( fifo ); +} + + +static int deinit_sdl(audio_output_t* ao) +{ + /* Free up memory */ + if (ao->userptr) { + free( ao->userptr ); + ao->userptr = NULL; + } + + /* Shut down SDL */ + SDL_Quit(); + + /* Success */ + return 0; +} + + +static int init_sdl(audio_output_t* ao) +{ + if (ao==NULL) return -1; + + /* Set callbacks */ + ao->open = open_sdl; + ao->flush = flush_sdl; + ao->write = write_sdl; + ao->get_formats = get_formats_sdl; + ao->close = close_sdl; + ao->deinit = deinit_sdl; + + /* Allocate memory */ + ao->userptr = malloc( sizeof(sfifo_t) ); + if (ao->userptr==NULL) { + error( "Failed to allocated memory for FIFO structure" ); + return -1; + } + memset( ao->userptr, 0, sizeof(sfifo_t) ); + + /* Initialise SDL */ + if (SDL_Init( SDL_INIT_AUDIO ) ) { + error1("Failed to initialise SDL: %s\n", SDL_GetError()); + return -1; + } + + /* Success */ + return 0; +} + + +/* + Module information data structure +*/ +mpg123_module_t mpg123_output_module_info = { + /* api_version */ MPG123_MODULE_API_VERSION, + /* name */ "sdl", + /* description */ "Output audio using SDL (Simple DirectMedia Layer).", + /* revision */ "$Rev:$", + /* handle */ NULL, + + /* init_output */ init_sdl, +}; |