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alsa.c
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alsa.c
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/*
alsa: sound output with Advanced Linux Sound Architecture 1.x API
copyright 2006-2016 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 Clemens Ladisch <clemens@ladisch.de>
*/
/* ALSA headers define struct timeval if no POSIX macro is set,
nicely in conflict with definitions in system headers. They had
a discussion about that a long time ago:
http://mailman.alsa-project.org/pipermail/alsa-devel/2007-June/001684.html
... seems like the conclusion was not carried through.
*/
#define _POSIX_SOURCE
/* Things are still missing if _DEFAULT_SOURCE is not defined (for recent
glibc, I presume. */
#define _DEFAULT_SOURCE
#include "out123_int.h"
#include <errno.h>
/* make ALSA 0.9.x compatible to the 1.0.x API */
#define ALSA_PCM_NEW_HW_PARAMS_API
#define ALSA_PCM_NEW_SW_PARAMS_API
#include <alloca.h> /* GCC complains about missing declaration of alloca. */
#include <alsa/asoundlib.h>
#include "debug.h"
/* Total buffer size in seconds, 0.2 is more true to what ALSA maximally uses
here (8192 samples). The earlier default of 0.5 was never true. */
#define BUFFER_LENGTH (ao->device_buffer > 0. ? ao->device_buffer : 0.2)
static const struct {
snd_pcm_format_t alsa;
int mpg123;
} format_map[] = {
{ SND_PCM_FORMAT_S16, MPG123_ENC_SIGNED_16 },
{ SND_PCM_FORMAT_U16, MPG123_ENC_UNSIGNED_16 },
{ SND_PCM_FORMAT_U8, MPG123_ENC_UNSIGNED_8 },
{ SND_PCM_FORMAT_S8, MPG123_ENC_SIGNED_8 },
{ SND_PCM_FORMAT_A_LAW, MPG123_ENC_ALAW_8 },
{ SND_PCM_FORMAT_MU_LAW, MPG123_ENC_ULAW_8 },
{ SND_PCM_FORMAT_S32, MPG123_ENC_SIGNED_32 },
{ SND_PCM_FORMAT_U32, MPG123_ENC_UNSIGNED_32 },
#ifdef WORDS_BIGENDIAN
{ SND_PCM_FORMAT_S24_3BE, MPG123_ENC_SIGNED_24 },
{ SND_PCM_FORMAT_U24_3BE, MPG123_ENC_UNSIGNED_24 },
#else
{ SND_PCM_FORMAT_S24_3LE, MPG123_ENC_SIGNED_24 },
{ SND_PCM_FORMAT_U24_3LE, MPG123_ENC_UNSIGNED_24 },
#endif
{ SND_PCM_FORMAT_FLOAT, MPG123_ENC_FLOAT_32 },
{ SND_PCM_FORMAT_FLOAT64, MPG123_ENC_FLOAT_64 }
};
#define NUM_FORMATS (sizeof format_map / sizeof format_map[0])
static int rates_match(long int desired, unsigned int actual)
{
return actual * 100 > desired * (100 - AUDIO_RATE_TOLERANCE) &&
actual * 100 < desired * (100 + AUDIO_RATE_TOLERANCE);
}
static int initialize_device(out123_handle *ao)
{
snd_pcm_hw_params_t *hw=NULL;
snd_pcm_sw_params_t *sw=NULL;
snd_pcm_uframes_t buffer_size;
snd_pcm_uframes_t period_size;
snd_pcm_format_t format;
snd_pcm_t *pcm=(snd_pcm_t*)ao->userptr;
unsigned int rate;
int i;
snd_pcm_hw_params_alloca(&hw); /* Ignore GCC warning here... alsa-lib>=1.0.16 doesn't trigger that anymore, too. */
if (snd_pcm_hw_params_any(pcm, hw) < 0) {
if(!AOQUIET) error("initialize_device(): no configuration available");
return -1;
}
if (snd_pcm_hw_params_set_access(pcm, hw, SND_PCM_ACCESS_RW_INTERLEAVED) < 0) {
if(!AOQUIET) error("initialize_device(): device does not support interleaved access");
return -1;
}
format = SND_PCM_FORMAT_UNKNOWN;
for (i = 0; i < NUM_FORMATS; ++i) {
if (ao->format == format_map[i].mpg123) {
format = format_map[i].alsa;
break;
}
}
if (format == SND_PCM_FORMAT_UNKNOWN) {
if(!AOQUIET) error1("initialize_device(): invalid sample format %d", ao->format);
errno = EINVAL;
return -1;
}
if (snd_pcm_hw_params_set_format(pcm, hw, format) < 0) {
if(!AOQUIET) error1("initialize_device(): cannot set format %s", snd_pcm_format_name(format));
return -1;
}
if (snd_pcm_hw_params_set_channels(pcm, hw, ao->channels) < 0) {
if(!AOQUIET) error1("initialize_device(): cannot set %d channels", ao->channels);
return -1;
}
rate = ao->rate;
if (snd_pcm_hw_params_set_rate_near(pcm, hw, &rate, NULL) < 0) {
if(!AOQUIET) error1("initialize_device(): cannot set rate %u", rate);
return -1;
}
if (!rates_match(ao->rate, rate)) {
if(!AOQUIET) error2("initialize_device(): rate %ld not available, using %u", ao->rate, rate);
/* return -1; */
}
buffer_size = rate * BUFFER_LENGTH;
if (snd_pcm_hw_params_set_buffer_size_near(pcm, hw, &buffer_size) < 0) {
if(!AOQUIET) error("initialize_device(): cannot set buffer size");
return -1;
}
debug1("buffer_size=%lu", (unsigned long)buffer_size);
period_size = buffer_size / 3; /* 3 periods is so much more common. */
if (snd_pcm_hw_params_set_period_size_near(pcm, hw, &period_size, NULL) < 0) {
if(!AOQUIET) error("initialize_device(): cannot set period size");
return -1;
}
debug1("period_size=%lu", (unsigned long)period_size);
if (snd_pcm_hw_params(pcm, hw) < 0) {
if(!AOQUIET) error("initialize_device(): cannot set hw params");
return -1;
}
snd_pcm_sw_params_alloca(&sw);
if (snd_pcm_sw_params_current(pcm, sw) < 0) {
if(!AOQUIET) error("initialize_device(): cannot get sw params");
return -1;
}
/* start playing right away */
if (snd_pcm_sw_params_set_start_threshold(pcm, sw, 1) < 0) {
if(!AOQUIET) error("initialize_device(): cannot set start threshold");
return -1;
}
/* wake up on every interrupt */
if (snd_pcm_sw_params_set_avail_min(pcm, sw, 1) < 0) {
if(!AOQUIET) error("initialize_device(): cannot set min available");
return -1;
}
#if SND_LIB_VERSION < ((1<<16)|16)
/* Always write as many frames as possible (deprecated since alsa-lib 1.0.16) */
if (snd_pcm_sw_params_set_xfer_align(pcm, sw, 1) < 0) {
if(!AOQUIET) error("initialize_device(): cannot set transfer alignment");
return -1;
}
#endif
if (snd_pcm_sw_params(pcm, sw) < 0) {
if(!AOQUIET) error("initialize_device(): cannot set sw params");
return -1;
}
return 0;
}
#ifndef DEBUG
static void error_ignorer(const char *file, int line, const char *function, int err, const char *fmt,...)
{
/* I can make ALSA silent. */
}
#endif
static int open_alsa(out123_handle *ao)
{
const char *pcm_name;
snd_pcm_t *pcm=NULL;
debug1("open_alsa with %p", ao->userptr);
#ifndef DEBUG
if(AOQUIET) snd_lib_error_set_handler(error_ignorer);
#endif
pcm_name = ao->device ? ao->device : "default";
if (snd_pcm_open(&pcm, pcm_name, SND_PCM_STREAM_PLAYBACK, 0) < 0) {
if(!AOQUIET) error1("cannot open device %s", pcm_name);
return -1;
}
ao->userptr = pcm;
if (ao->format != -1) {
/* we're going to play: initalize sample format */
return initialize_device(ao);
} else {
/* query mode; sample format will be set for each query */
return 0;
}
}
static int get_formats_alsa(out123_handle *ao)
{
snd_pcm_t *pcm=(snd_pcm_t*)ao->userptr;
snd_pcm_hw_params_t *hw;
unsigned int rate;
int supported_formats, i;
snd_pcm_hw_params_alloca(&hw);
if (snd_pcm_hw_params_any(pcm, hw) < 0) {
if(!AOQUIET) error("get_formats_alsa(): no configuration available");
return -1;
}
if (snd_pcm_hw_params_set_access(pcm, hw, SND_PCM_ACCESS_RW_INTERLEAVED) < 0)
return -1;
if (snd_pcm_hw_params_set_channels(pcm, hw, ao->channels) < 0)
return 0;
rate = ao->rate;
if (snd_pcm_hw_params_set_rate_near(pcm, hw, &rate, NULL) < 0)
return -1;
if (!rates_match(ao->rate, rate))
return 0;
supported_formats = 0;
for (i = 0; i < NUM_FORMATS; ++i) {
if (snd_pcm_hw_params_test_format(pcm, hw, format_map[i].alsa) == 0)
supported_formats |= format_map[i].mpg123;
}
return supported_formats;
}
static int write_alsa(out123_handle *ao, unsigned char *buf, int bytes)
{
snd_pcm_t *pcm=(snd_pcm_t*)ao->userptr;
snd_pcm_uframes_t frames;
snd_pcm_sframes_t written;
frames = snd_pcm_bytes_to_frames(pcm, bytes);
while
( /* Try to write, recover if error, try again if recovery successful. */
(written = snd_pcm_writei(pcm, buf, frames)) < 0
&& snd_pcm_recover(pcm, (int)written, 0) == 0
)
{
debug2("recovered from alsa issue %i while trying to write %lu frames", (int)written, (unsigned long)frames);
}
if(written < 0)
{
error1("Fatal problem with alsa output, error %i.", (int)written);
return -1;
}
else return snd_pcm_frames_to_bytes(pcm, written);
}
static void flush_alsa(out123_handle *ao)
{
snd_pcm_t *pcm=(snd_pcm_t*)ao->userptr;
/* is this the optimal solution? - we should figure out what we really whant from this function */
debug("alsa drop");
snd_pcm_drop(pcm);
debug("alsa prepare");
snd_pcm_prepare(pcm);
debug("alsa flush done");
}
static void drain_alsa(out123_handle *ao)
{
snd_pcm_t *pcm=(snd_pcm_t*)ao->userptr;
debug1("drain_alsa with %p", ao->userptr);
snd_pcm_drain(pcm);
}
static int close_alsa(out123_handle *ao)
{
snd_pcm_t *pcm=(snd_pcm_t*)ao->userptr;
debug1("close_alsa with %p", ao->userptr);
if(pcm != NULL) /* be really generous for being called without any device opening */
{
ao->userptr = NULL; /* Should alsa do this or the module wrapper? */
return snd_pcm_close(pcm);
}
else return 0;
}
static int init_alsa(out123_handle* ao)
{
if (ao==NULL) return -1;
/* Set callbacks */
ao->open = open_alsa;
ao->flush = flush_alsa;
ao->drain = drain_alsa;
ao->write = write_alsa;
ao->get_formats = get_formats_alsa;
ao->close = close_alsa;
/* Success */
return 0;
}
/*
Module information data structure
*/
mpg123_module_t mpg123_output_module_info = {
/* api_version */ MPG123_MODULE_API_VERSION,
/* name */ "alsa",
/* description */ "Output audio using Advanced Linux Sound Architecture (ALSA).",
/* revision */ "$Rev:$",
/* handle */ NULL,
/* init_output */ init_alsa,
};