/*
* Copyright (C) 2003-2013 The Music Player Daemon Project
* http://www.musicpd.org
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
/*
* ALSA code based on an example by Paul Davis released under GPL here:
* http://equalarea.com/paul/alsa-audio.html
* and one by Matthias Nagorni, also GPL, here:
* http://alsamodular.sourceforge.net/alsa_programming_howto.html
*/
#include "config.h"
#include "AlsaInputPlugin.hxx"
#include "InputPlugin.hxx"
#include "InputStream.hxx"
#include "util/Domain.hxx"
#include "util/Error.hxx"
#include "util/StringUtil.hxx"
#include "Log.hxx"
#include <alsa/asoundlib.h>
static constexpr Domain alsa_input_domain("alsa");
static constexpr const char *default_device = "hw:0,0";
// this value chosen to balance between limiting latency and avoiding stutter
static constexpr int max_frames_to_buffer = 64;
// the following defaults are because the PcmDecoderPlugin forces CD format
static constexpr snd_pcm_format_t default_format = SND_PCM_FORMAT_S16;
static constexpr int default_channels = 2; // stereo
static constexpr unsigned int default_rate = 44100; // cd quality
struct AlsaInputStream {
InputStream base;
snd_pcm_t *capture_handle;
size_t frame_size;
size_t max_bytes_to_read;
AlsaInputStream(const char *uri, Mutex &mutex, Cond &cond,
snd_pcm_t *handle)
:base(input_plugin_alsa, uri, mutex, cond),
capture_handle(handle) {
frame_size = snd_pcm_format_width(default_format) / 8 * default_channels;
max_bytes_to_read = max_frames_to_buffer * frame_size;
base.mime = strdup("audio/x-mpd-cdda-pcm");
base.seekable = false;
base.size = -1;
base.ready = true;
}
~AlsaInputStream() {
snd_pcm_close(capture_handle);
}
};
static InputStream *
alsa_input_open(const char *uri, Mutex &mutex, Cond &cond, Error &error)
{
int err;
// check uri is appropriate for alsa input
if (!StringStartsWith(uri, "alsa://"))
return nullptr;
const char *device = uri + 7;
if (device[0] == '\0')
device = default_device;
snd_pcm_t *capture_handle;
if ((err = snd_pcm_open(&capture_handle, device,
SND_PCM_STREAM_CAPTURE, 0)) < 0) {
error.Format(alsa_input_domain, "Failed to open device: %s (%s)", device, snd_strerror(err));
return nullptr;
}
snd_pcm_hw_params_t *hw_params;
if ((err = snd_pcm_hw_params_malloc(&hw_params)) < 0) {
error.Format(alsa_input_domain, "Cannot allocate hardware parameter structure (%s)", snd_strerror(err));
snd_pcm_close(capture_handle);
return nullptr;
}
if ((err = snd_pcm_hw_params_any(capture_handle, hw_params)) < 0) {
error.Format(alsa_input_domain, "Cannot initialize hardware parameter structure (%s)", snd_strerror(err));
snd_pcm_hw_params_free(hw_params);
snd_pcm_close(capture_handle);
return nullptr;
}
if ((err = snd_pcm_hw_params_set_access(capture_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
error.Format(alsa_input_domain, "Cannot set access type (%s)", snd_strerror (err));
snd_pcm_hw_params_free (hw_params);
snd_pcm_close(capture_handle);
return nullptr;
}
if ((err = snd_pcm_hw_params_set_format(capture_handle, hw_params, default_format)) < 0) {
snd_pcm_hw_params_free(hw_params);
snd_pcm_close(capture_handle);
error.Format(alsa_input_domain, "Cannot set sample format (%s)", snd_strerror (err));
return nullptr;
}
if ((err = snd_pcm_hw_params_set_channels(capture_handle, hw_params, default_channels)) < 0) {
snd_pcm_hw_params_free(hw_params);
snd_pcm_close(capture_handle);
error.Format(alsa_input_domain, "Cannot set channels (%s)", snd_strerror (err));
return nullptr;
}
if ((err = snd_pcm_hw_params_set_rate(capture_handle, hw_params, default_rate, 0)) < 0) {
snd_pcm_hw_params_free(hw_params);
snd_pcm_close(capture_handle);
error.Format(alsa_input_domain, "Cannot set sample rate (%s)", snd_strerror (err));
return nullptr;
}
if ((err = snd_pcm_hw_params(capture_handle, hw_params)) < 0) {
error.Format(alsa_input_domain, "Cannot set parameters (%s)", snd_strerror (err));
snd_pcm_hw_params_free(hw_params);
snd_pcm_close(capture_handle);
return nullptr;
}
snd_pcm_hw_params_free (hw_params);
// clear any data already in the PCM buffer
if ((err = snd_pcm_drop(capture_handle)) < 0) {
error.Format(alsa_input_domain, "Cannot clear PCM buffer (%s)", snd_strerror (err));
snd_pcm_hw_params_free(hw_params);
snd_pcm_close(capture_handle);
return nullptr;
}
AlsaInputStream *ais = new AlsaInputStream(uri, mutex, cond, capture_handle);
return &ais->base;
}
static void
alsa_input_close(InputStream *is)
{
AlsaInputStream *ais = (AlsaInputStream*) is;
delete ais;
}
static size_t
alsa_input_read(InputStream *is, void *ptr, size_t size,
gcc_unused Error &error)
{
AlsaInputStream *ais = (AlsaInputStream*) is;
int num_frames = max_frames_to_buffer;
if (size < ais->max_bytes_to_read)
// calculate number of whole frames that will fit in size bytes
num_frames = size / ais->frame_size;
int ret;
while ((ret = snd_pcm_readi(ais->capture_handle, ptr,
num_frames)) < 0) {
snd_pcm_prepare(ais->capture_handle);
LogDebug(alsa_input_domain, "Buffer Overrun");
}
size_t nbytes = ret == max_frames_to_buffer
? ais->max_bytes_to_read
: ret * ais->frame_size;
is->offset += nbytes;
return nbytes;
}
static bool
alsa_input_eof(gcc_unused InputStream *is)
{
return false;
};
const struct InputPlugin input_plugin_alsa = {
"alsa",
nullptr,
nullptr,
alsa_input_open,
alsa_input_close,
nullptr,
nullptr,
nullptr,
nullptr,
alsa_input_read,
alsa_input_eof,
nullptr,
};
