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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/***************************************************************************
* alsa.cc
*
* Do 21. Jan 16:48:32 CET 2016
* Copyright 2016 Christian Glöckner
* cgloeckner@freenet.de
****************************************************************************/
/*
* This file is part of DrumGizmo.
*
* DrumGizmo is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* DrumGizmo 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with DrumGizmo; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
#include <iostream>
#include "alsa.h"
int const BUFFER_SIZE = 40960;
struct AlsaInitError
{
int const code;
const std::string msg;
AlsaInitError(int op_code, const std::string& msg)
: code{code}
, msg{msg}
{
}
static inline void test(int code, const std::string& msg)
{
if(code < 0)
{
throw AlsaInitError(code, msg);
}
}
};
AlsaOutputEngine::AlsaOutputEngine()
: handle{nullptr}
, params{nullptr}
, data{}
, num_channels{0u}
, dev{"default"}
, srate{44100}
, frames{32}
{
}
AlsaOutputEngine::~AlsaOutputEngine()
{
// note: do NOT release `params`, it was allocated by `alloca()`
if(handle != nullptr)
{
snd_pcm_close(handle);
}
}
bool AlsaOutputEngine::init(const Channels& channels)
{
// try to initialize alsa
try
{
int value =
snd_pcm_open(&handle, dev.c_str(), SND_PCM_STREAM_PLAYBACK, 0);
AlsaInitError::test(value, "snd_pcm_open");
num_channels = channels.size();
if(handle == nullptr)
{
std::cerr << "[AlsaOutputEngine] Failed to acquire "
<< "hardware handle\n";
return false;
}
// Allocate and init a hardware parameters object
snd_pcm_hw_params_alloca(¶ms);
value = snd_pcm_hw_params_any(handle, params);
AlsaInitError::test(value, "snd_pcm_hw_params_any");
value = snd_pcm_hw_params_set_access(
handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
AlsaInitError::test(value, "snd_pcm_hw_params_set_access");
value =
snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_FLOAT);
AlsaInitError::test(value, "snd_pcm_hw_params_set_format");
value = snd_pcm_hw_params_set_channels(handle, params, num_channels);
AlsaInitError::test(value, "snd_pcm_hw_params_set_channels");
value = snd_pcm_hw_params_set_rate_near(handle, params, &srate, 0);
AlsaInitError::test(value, "snd_pcm_hw_params_set_rate_near");
value =
snd_pcm_hw_params_set_period_size_near(handle, params, &frames, 0);
AlsaInitError::test(value, "snd_pcm_hw_params_set_period_size_near");
value = snd_pcm_hw_params(handle, params);
AlsaInitError::test(value, "snd_pcm_hw_params");
}
catch(AlsaInitError const& error)
{
std::cerr << "[AlsaOutputEngine] " << error.msg
<< " failed: " << snd_strerror(error.code) << std::endl;
return false;
}
data.clear();
data.resize(BUFFER_SIZE * num_channels);
return true;
}
void AlsaOutputEngine::setParm(const std::string& parm, const std::string& value)
{
if(parm == "dev")
{
// apply hardware device name
dev = value;
}
else if(parm == "frames")
{
// try to apply hardware buffer size
try
{
frames = std::stoi(value);
}
catch(...)
{
std::cerr << "[AlsaOutputEngine] Invalid buffer size " << value
<< "\n";
}
}
else if(parm == "srate")
{
try
{
srate = std::stoi(value);
}
catch(...)
{
std::cerr << "[AlsaOutputEngine] Invalid samplerate " << value
<< "\n";
}
}
else
{
std::cerr << "[AlsaOutputEngine] Unsupported parameter '" << parm
<< "'\n";
}
}
bool AlsaOutputEngine::start()
{
return true;
}
void AlsaOutputEngine::stop()
{
}
void AlsaOutputEngine::pre(size_t nsamples)
{
}
void AlsaOutputEngine::run(int ch, sample_t* samples, size_t nsamples)
{
// Write channel data in interleaved buffer
for(auto i = 0u; i < nsamples; ++i)
{
data[i * num_channels + ch] = samples[i];
}
}
void AlsaOutputEngine::post(size_t nsamples)
{
// Write the interleaved buffer to the soundcard
snd_pcm_writei(handle, data.data(), nsamples);
}
size_t AlsaOutputEngine::samplerate()
{
return srate;
}
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