drumgizmo/output/alsa.cc


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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 Gl�ckner
 *  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 General Public License as published by
 *  the Free Software Foundation; either version 2 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU 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;
	std::string const msg;
	
	AlsaInitError(int op_code, std::string const & msg)
		: code{code}
		, msg{msg} {
	}
	
	static inline void test(int code, std::string const & 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(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(&params);
		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(std::string parm, 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;
}