drivers/audio/AudioOutputDevice.cpp

/***************************************************************************
 *                                                                         *
 *   LinuxSampler - modular, streaming capable sampler                     *
 *                                                                         *
 *   Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck   *
 *   Copyright (C) 2005 - 2008 Christian Schoenebeck                       *
 *                                                                         *
 *   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., 59 Temple Place, Suite 330, Boston,                 *
 *   MA  02111-1307  USA                                                   *
 ***************************************************************************/

#include "AudioOutputDeviceFactory.h"
#include "AudioOutputDevice.h"
#include "../../common/global_private.h"

namespace LinuxSampler {

// *************** ParameterActive ***************
// *

    AudioOutputDevice::ParameterActive::ParameterActive() : DeviceCreationParameterBool() {
        InitWithDefault();
    }

    AudioOutputDevice::ParameterActive::ParameterActive(String s) : DeviceCreationParameterBool(s) {
    }

    String AudioOutputDevice::ParameterActive::Description() {
        return "Enable / disable device";
    }

    bool AudioOutputDevice::ParameterActive::Fix() {
        return false;
    }

    bool AudioOutputDevice::ParameterActive::Mandatory() {
        return false;
    }

    std::map<String,DeviceCreationParameter*> AudioOutputDevice::ParameterActive::DependsAsParameters() {
        return std::map<String,DeviceCreationParameter*>();
    }

    optional<bool> AudioOutputDevice::ParameterActive::DefaultAsBool(std::map<String,String> Parameters) {
        return true;
    }

    void AudioOutputDevice::ParameterActive::OnSetValue(bool b) throw (Exception) {
        if (b) ((AudioOutputDevice*)pDevice)->Play();
        else ((AudioOutputDevice*)pDevice)->Stop();
    }

    String AudioOutputDevice::ParameterActive::Name() {
        return "ACTIVE";
    }


// *************** ParameterSampleRate ***************
// *

    AudioOutputDevice::ParameterSampleRate::ParameterSampleRate() : DeviceCreationParameterInt() {
        InitWithDefault();
    }

    AudioOutputDevice::ParameterSampleRate::ParameterSampleRate(String s) : DeviceCreationParameterInt(s) {
    }

    String AudioOutputDevice::ParameterSampleRate::Description() {
        return "Output sample rate";
    }

    bool AudioOutputDevice::ParameterSampleRate::Fix() {
        return true;
    }

    bool AudioOutputDevice::ParameterSampleRate::Mandatory() {
        return false;
    }

    std::map<String,DeviceCreationParameter*> AudioOutputDevice::ParameterSampleRate::DependsAsParameters() {
        return std::map<String,DeviceCreationParameter*>();
    }

    optional<int> AudioOutputDevice::ParameterSampleRate::DefaultAsInt(std::map<String,String> Parameters) {
        return 44100;
    }

    optional<int> AudioOutputDevice::ParameterSampleRate::RangeMinAsInt(std::map<String,String> Parameters) {
        return optional<int>::nothing;
    }

    optional<int> AudioOutputDevice::ParameterSampleRate::RangeMaxAsInt(std::map<String,String> Parameters) {
        return optional<int>::nothing;
    }

    std::vector<int> AudioOutputDevice::ParameterSampleRate::PossibilitiesAsInt(std::map<String,String> Parameters) {
        return std::vector<int>();
    }

    int AudioOutputDevice::ParameterSampleRate::ValueAsInt() {
        return (pDevice) ? (int) ((AudioOutputDevice*)pDevice)->SampleRate()
                         : DeviceCreationParameterInt::ValueAsInt();
    }

    void AudioOutputDevice::ParameterSampleRate::OnSetValue(int i) throw (Exception) {
        /* cannot happen, as parameter is fix */
    }

    String AudioOutputDevice::ParameterSampleRate::Name() {
        return "SAMPLERATE";
    }


// *************** ParameterChannels ***************
// *

    AudioOutputDevice::ParameterChannels::ParameterChannels() : DeviceCreationParameterInt() {
       InitWithDefault();
    }

    AudioOutputDevice::ParameterChannels::ParameterChannels(String s) : DeviceCreationParameterInt(s) {
    }

    String AudioOutputDevice::ParameterChannels::Description() {
        return "Number of output channels";
    }

    bool AudioOutputDevice::ParameterChannels::Fix() {
        return false;
    }

    bool AudioOutputDevice::ParameterChannels::Mandatory() {
        return false;
    }

    std::map<String,DeviceCreationParameter*> AudioOutputDevice::ParameterChannels::DependsAsParameters() {
        return std::map<String,DeviceCreationParameter*>();
    }

    optional<int> AudioOutputDevice::ParameterChannels::DefaultAsInt(std::map<String,String> Parameters) {
        return 2;
    }

    optional<int> AudioOutputDevice::ParameterChannels::RangeMinAsInt(std::map<String,String> Parameters) {
        return 1;
    }

    optional<int> AudioOutputDevice::ParameterChannels::RangeMaxAsInt(std::map<String,String> Parameters) {
        return optional<int>::nothing;
    }

    std::vector<int> AudioOutputDevice::ParameterChannels::PossibilitiesAsInt(std::map<String,String> Parameters) {
        return std::vector<int>();
    }

    void AudioOutputDevice::ParameterChannels::OnSetValue(int i) throw (Exception) {
        ((AudioOutputDevice*)pDevice)->AcquireChannels(i);
    }

    String AudioOutputDevice::ParameterChannels::Name() {
        return "CHANNELS";
    }


// *************** AudioOutputDevice ***************
// *

    AudioOutputDevice::AudioOutputDevice(std::map<String,DeviceCreationParameter*> DriverParameters)
        : EnginesReader(Engines) {
        this->Parameters = DriverParameters;
    }

    AudioOutputDevice::~AudioOutputDevice() {
        // delete all audio channels
        {
            std::vector<AudioChannel*>::iterator iter = Channels.begin();
            while (iter != Channels.end()) {
                delete *iter;
                iter++;
            }
            Channels.clear();
        }

        // delete all device parameters
        {
            std::map<String,DeviceCreationParameter*>::iterator iter = Parameters.begin();
            while (iter != Parameters.end()) {
                delete iter->second;
                iter++;
            }
            Parameters.clear();
        }

        // delete all master effect chains
        {
            std::vector<EffectChain*>::iterator iter = vEffectChains.begin();
            while (iter != vEffectChains.end()) {
                delete *iter;
                iter++;
            }
            vEffectChains.clear();
        }
    }

    void AudioOutputDevice::Connect(Engine* pEngine) {
        std::set<Engine*>& engines = Engines.GetConfigForUpdate();
        if (engines.find(pEngine) == engines.end()) {
            engines.insert(pEngine);
            Engines.SwitchConfig().insert(pEngine);
            // make sure the engine knows about the connection
            //pEngine->Connect(this);
        }
    }

    void AudioOutputDevice::Disconnect(Engine* pEngine) {
        std::set<Engine*>& engines = Engines.GetConfigForUpdate();
        if (engines.find(pEngine) != engines.end()) { // if clause to prevent disconnect loop
            engines.erase(pEngine);
            Engines.SwitchConfig().erase(pEngine);
            // make sure the engine knows about the disconnection
            //pEngine->DisconnectAudioOutputDevice();
        }
    }

    AudioChannel* AudioOutputDevice::Channel(uint ChannelIndex) {
        return (ChannelIndex < Channels.size()) ? Channels[ChannelIndex] : NULL;
    }

    void AudioOutputDevice::AcquireChannels(uint Channels) {
        if (Channels > this->Channels.size()) {
            for (int c = this->Channels.size(); c < Channels; c++) {
                this->Channels.push_back(CreateChannel(c));
            }
        }
    }

    uint AudioOutputDevice::ChannelCount() {
        return Channels.size();
    }

    std::map<String,DeviceCreationParameter*> AudioOutputDevice::DeviceParameters() {
        return Parameters;
    }

    EffectChain* AudioOutputDevice::AddMasterEffectChain() {
        EffectChain* pChain = new EffectChain(this);
        vEffectChains.push_back(pChain);
        return pChain;
    }

    void AudioOutputDevice::RemoveMasterEffectChain(uint iChain) throw (Exception) {
        if (iChain >= vEffectChains.size())
            throw Exception(
                "Could not remove master effect chain " + ToString(iChain) +
                ", index out of bounds"
            );
        std::vector<EffectChain*>::iterator iter = vEffectChains.begin();
        for (int i = 0; i < iChain; ++i) ++iter;
        vEffectChains.erase(iter);
    }

    EffectChain* AudioOutputDevice::MasterEffectChain(uint iChain) const {
        if (iChain >= vEffectChains.size()) return NULL;
        return vEffectChains[iChain];
    }

    uint AudioOutputDevice::MasterEffectChainCount() const {
        return vEffectChains.size();
    }

    int AudioOutputDevice::RenderAudio(uint Samples) {
        if (Channels.empty()) return 0;

        // reset all channels with silence
        {
            std::vector<AudioChannel*>::iterator iterChannels = Channels.begin();
            std::vector<AudioChannel*>::iterator end          = Channels.end();
            for (; iterChannels != end; iterChannels++)
                (*iterChannels)->Clear(); // zero out audio buffer
        }
        // do the same for master effects
        {
            std::vector<EffectChain*>::iterator iterChains = vEffectChains.begin();
            std::vector<EffectChain*>::iterator end        = vEffectChains.end();
            for (; iterChains != end; ++iterChains)
                (*iterChains)->ClearAllChannels(); // zero out audio buffers
        }

        int result = 0;

        // let all connected engines render audio for the current audio fragment cycle
        const std::set<Engine*>& engines = EnginesReader.Lock();
        #if CONFIG_RT_EXCEPTIONS
        try
        #endif // CONFIG_RT_EXCEPTIONS
        {
            std::set<Engine*>::iterator iterEngine = engines.begin();
            std::set<Engine*>::iterator end        = engines.end();
            for (; iterEngine != end; iterEngine++) {
                int res = (*iterEngine)->RenderAudio(Samples);
                if (res != 0) result = res;
            }
        }
        #if CONFIG_RT_EXCEPTIONS
        catch (std::runtime_error se) {
            std::cerr << "std::runtime_error: " << se.what() << std::endl << std::flush;
            exit(EXIT_FAILURE);
        }
        #endif // CONFIG_RT_EXCEPTIONS
        EnginesReader.Unlock();

        // now that the engines (might) have left fx send signals for master
        // effects, render all master effects
        {
            std::vector<EffectChain*>::iterator iterChains = vEffectChains.begin();
            std::vector<EffectChain*>::iterator end        = vEffectChains.end();
            for (; iterChains != end; ++iterChains) {
                if (!(*iterChains)->EffectCount()) continue;
                (*iterChains)->RenderAudio(Samples);
                // mix the result of the last effect in the chain to the audio
                // output device channel(s)
                Effect* pLastEffect =
                    (*iterChains)->GetEffect((*iterChains)->EffectCount() - 1);
                for (int iChan = 0; iChan < pLastEffect->OutputChannelCount() && iChan < ChannelCount(); ++iChan)
                    pLastEffect->OutputChannel(iChan)->MixTo(Channel(iChan), Samples);
            }
        }

        return result;
    }

    int AudioOutputDevice::RenderSilence(uint Samples) {
        if (Channels.empty()) return 0;

        // reset all channels with silence
        {
            std::vector<AudioChannel*>::iterator iterChannels = Channels.begin();
            std::vector<AudioChannel*>::iterator end          = Channels.end();
            for (; iterChannels != end; iterChannels++)
                (*iterChannels)->Clear(); // zero out audio buffer
        }

        return 0;
    }

} // namespace LinuxSampler
1	/***************************************************************************
2	* *
3	* LinuxSampler - modular, streaming capable sampler *
4	* *
5	* Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck *
6	* Copyright (C) 2005 - 2008 Christian Schoenebeck *
7	* *
8	* This program is free software; you can redistribute it and/or modify *
9	* it under the terms of the GNU General Public License as published by *
10	* the Free Software Foundation; either version 2 of the License, or *
11	* (at your option) any later version. *
12	* *
13	* This program is distributed in the hope that it will be useful, *
14	* but WITHOUT ANY WARRANTY; without even the implied warranty of *
15	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
16	* GNU General Public License for more details. *
17	* *
18	* You should have received a copy of the GNU General Public License *
19	* along with this program; if not, write to the Free Software *
20	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, *
21	* MA 02111-1307 USA *
22	***************************************************************************/
23
24	#include "AudioOutputDeviceFactory.h"
25	#include "AudioOutputDevice.h"
26	#include "../../common/global_private.h"
27
28	namespace LinuxSampler {
29
30	// ************* ParameterActive *************
31	// *
32
33	AudioOutputDevice::ParameterActive::ParameterActive() : DeviceCreationParameterBool() {
34	InitWithDefault();
35	}
36
37	AudioOutputDevice::ParameterActive::ParameterActive(String s) : DeviceCreationParameterBool(s) {
38	}
39
40	String AudioOutputDevice::ParameterActive::Description() {
41	return "Enable / disable device";
42	}
43
44	bool AudioOutputDevice::ParameterActive::Fix() {
45	return false;
46	}
47
48	bool AudioOutputDevice::ParameterActive::Mandatory() {
49	return false;
50	}
51
52	std::map<String,DeviceCreationParameter*> AudioOutputDevice::ParameterActive::DependsAsParameters() {
53	return std::map<String,DeviceCreationParameter*>();
54	}
55
56	optional<bool> AudioOutputDevice::ParameterActive::DefaultAsBool(std::map<String,String> Parameters) {
57	return true;
58	}
59
60	void AudioOutputDevice::ParameterActive::OnSetValue(bool b) throw (Exception) {
61	if (b) ((AudioOutputDevice*)pDevice)->Play();
62	else ((AudioOutputDevice*)pDevice)->Stop();
63	}
64
65	String AudioOutputDevice::ParameterActive::Name() {
66	return "ACTIVE";
67	}
68
69
70
71	// ************* ParameterSampleRate *************
72	// *
73
74	AudioOutputDevice::ParameterSampleRate::ParameterSampleRate() : DeviceCreationParameterInt() {
75	InitWithDefault();
76	}
77
78	AudioOutputDevice::ParameterSampleRate::ParameterSampleRate(String s) : DeviceCreationParameterInt(s) {
79	}
80
81	String AudioOutputDevice::ParameterSampleRate::Description() {
82	return "Output sample rate";
83	}
84
85	bool AudioOutputDevice::ParameterSampleRate::Fix() {
86	return true;
87	}
88
89	bool AudioOutputDevice::ParameterSampleRate::Mandatory() {
90	return false;
91	}
92
93	std::map<String,DeviceCreationParameter*> AudioOutputDevice::ParameterSampleRate::DependsAsParameters() {
94	return std::map<String,DeviceCreationParameter*>();
95	}
96
97	optional<int> AudioOutputDevice::ParameterSampleRate::DefaultAsInt(std::map<String,String> Parameters) {
98	return 44100;
99	}
100
101	optional<int> AudioOutputDevice::ParameterSampleRate::RangeMinAsInt(std::map<String,String> Parameters) {
102	return optional<int>::nothing;
103	}
104
105	optional<int> AudioOutputDevice::ParameterSampleRate::RangeMaxAsInt(std::map<String,String> Parameters) {
106	return optional<int>::nothing;
107	}
108
109	std::vector<int> AudioOutputDevice::ParameterSampleRate::PossibilitiesAsInt(std::map<String,String> Parameters) {
110	return std::vector<int>();
111	}
112
113	int AudioOutputDevice::ParameterSampleRate::ValueAsInt() {
114	return (pDevice) ? (int) ((AudioOutputDevice*)pDevice)->SampleRate()
115	: DeviceCreationParameterInt::ValueAsInt();
116	}
117
118	void AudioOutputDevice::ParameterSampleRate::OnSetValue(int i) throw (Exception) {
119	/* cannot happen, as parameter is fix */
120	}
121
122	String AudioOutputDevice::ParameterSampleRate::Name() {
123	return "SAMPLERATE";
124	}
125
126
127
128	// ************* ParameterChannels *************
129	// *
130
131	AudioOutputDevice::ParameterChannels::ParameterChannels() : DeviceCreationParameterInt() {
132	InitWithDefault();
133	}
134
135	AudioOutputDevice::ParameterChannels::ParameterChannels(String s) : DeviceCreationParameterInt(s) {
136	}
137
138	String AudioOutputDevice::ParameterChannels::Description() {
139	return "Number of output channels";
140	}
141
142	bool AudioOutputDevice::ParameterChannels::Fix() {
143	return false;
144	}
145
146	bool AudioOutputDevice::ParameterChannels::Mandatory() {
147	return false;
148	}
149
150	std::map<String,DeviceCreationParameter*> AudioOutputDevice::ParameterChannels::DependsAsParameters() {
151	return std::map<String,DeviceCreationParameter*>();
152	}
153
154	optional<int> AudioOutputDevice::ParameterChannels::DefaultAsInt(std::map<String,String> Parameters) {
155	return 2;
156	}
157
158	optional<int> AudioOutputDevice::ParameterChannels::RangeMinAsInt(std::map<String,String> Parameters) {
159	return 1;
160	}
161
162	optional<int> AudioOutputDevice::ParameterChannels::RangeMaxAsInt(std::map<String,String> Parameters) {
163	return optional<int>::nothing;
164	}
165
166	std::vector<int> AudioOutputDevice::ParameterChannels::PossibilitiesAsInt(std::map<String,String> Parameters) {
167	return std::vector<int>();
168	}
169
170	void AudioOutputDevice::ParameterChannels::OnSetValue(int i) throw (Exception) {
171	((AudioOutputDevice*)pDevice)->AcquireChannels(i);
172	}
173
174	String AudioOutputDevice::ParameterChannels::Name() {
175	return "CHANNELS";
176	}
177
178
179
180	// ************* AudioOutputDevice *************
181	// *
182
183	AudioOutputDevice::AudioOutputDevice(std::map<String,DeviceCreationParameter*> DriverParameters)
184	: EnginesReader(Engines) {
185	this->Parameters = DriverParameters;
186	}
187
188	AudioOutputDevice::~AudioOutputDevice() {
189	// delete all audio channels
190	{
191	std::vector<AudioChannel*>::iterator iter = Channels.begin();
192	while (iter != Channels.end()) {
193	delete *iter;
194	iter++;
195	}
196	Channels.clear();
197	}
198
199	// delete all device parameters
200	{
201	std::map<String,DeviceCreationParameter*>::iterator iter = Parameters.begin();
202	while (iter != Parameters.end()) {
203	delete iter->second;
204	iter++;
205	}
206	Parameters.clear();
207	}
208
209	// delete all master effect chains
210	{
211	std::vector<EffectChain*>::iterator iter = vEffectChains.begin();
212	while (iter != vEffectChains.end()) {
213	delete *iter;
214	iter++;
215	}
216	vEffectChains.clear();
217	}
218	}
219
220	void AudioOutputDevice::Connect(Engine* pEngine) {
221	std::set<Engine*>& engines = Engines.GetConfigForUpdate();
222	if (engines.find(pEngine) == engines.end()) {
223	engines.insert(pEngine);
224	Engines.SwitchConfig().insert(pEngine);
225	// make sure the engine knows about the connection
226	//pEngine->Connect(this);
227	}
228	}
229
230	void AudioOutputDevice::Disconnect(Engine* pEngine) {
231	std::set<Engine*>& engines = Engines.GetConfigForUpdate();
232	if (engines.find(pEngine) != engines.end()) { // if clause to prevent disconnect loop
233	engines.erase(pEngine);
234	Engines.SwitchConfig().erase(pEngine);
235	// make sure the engine knows about the disconnection
236	//pEngine->DisconnectAudioOutputDevice();
237	}
238	}
239
240	AudioChannel* AudioOutputDevice::Channel(uint ChannelIndex) {
241	return (ChannelIndex < Channels.size()) ? Channels[ChannelIndex] : NULL;
242	}
243
244	void AudioOutputDevice::AcquireChannels(uint Channels) {
245	if (Channels > this->Channels.size()) {
246	for (int c = this->Channels.size(); c < Channels; c++) {
247	this->Channels.push_back(CreateChannel(c));
248	}
249	}
250	}
251
252	uint AudioOutputDevice::ChannelCount() {
253	return Channels.size();
254	}
255
256	std::map<String,DeviceCreationParameter*> AudioOutputDevice::DeviceParameters() {
257	return Parameters;
258	}
259
260	EffectChain* AudioOutputDevice::AddMasterEffectChain() {
261	EffectChain* pChain = new EffectChain(this);
262	vEffectChains.push_back(pChain);
263	return pChain;
264	}
265
266	void AudioOutputDevice::RemoveMasterEffectChain(uint iChain) throw (Exception) {
267	if (iChain >= vEffectChains.size())
268	throw Exception(
269	"Could not remove master effect chain " + ToString(iChain) +
270	", index out of bounds"
271	);
272	std::vector<EffectChain*>::iterator iter = vEffectChains.begin();
273	for (int i = 0; i < iChain; ++i) ++iter;
274	vEffectChains.erase(iter);
275	}
276
277	EffectChain* AudioOutputDevice::MasterEffectChain(uint iChain) const {
278	if (iChain >= vEffectChains.size()) return NULL;
279	return vEffectChains[iChain];
280	}
281
282	uint AudioOutputDevice::MasterEffectChainCount() const {
283	return vEffectChains.size();
284	}
285
286	int AudioOutputDevice::RenderAudio(uint Samples) {
287	if (Channels.empty()) return 0;
288
289	// reset all channels with silence
290	{
291	std::vector<AudioChannel*>::iterator iterChannels = Channels.begin();
292	std::vector<AudioChannel*>::iterator end = Channels.end();
293	for (; iterChannels != end; iterChannels++)
294	(*iterChannels)->Clear(); // zero out audio buffer
295	}
296	// do the same for master effects
297	{
298	std::vector<EffectChain*>::iterator iterChains = vEffectChains.begin();
299	std::vector<EffectChain*>::iterator end = vEffectChains.end();
300	for (; iterChains != end; ++iterChains)
301	(*iterChains)->ClearAllChannels(); // zero out audio buffers
302	}
303
304	int result = 0;
305
306	// let all connected engines render audio for the current audio fragment cycle
307	const std::set<Engine*>& engines = EnginesReader.Lock();
308	#if CONFIG_RT_EXCEPTIONS
309	try
310	#endif // CONFIG_RT_EXCEPTIONS
311	{
312	std::set<Engine*>::iterator iterEngine = engines.begin();
313	std::set<Engine*>::iterator end = engines.end();
314	for (; iterEngine != end; iterEngine++) {
315	int res = (*iterEngine)->RenderAudio(Samples);
316	if (res != 0) result = res;
317	}
318	}
319	#if CONFIG_RT_EXCEPTIONS
320	catch (std::runtime_error se) {
321	std::cerr << "std::runtime_error: " << se.what() << std::endl << std::flush;
322	exit(EXIT_FAILURE);
323	}
324	#endif // CONFIG_RT_EXCEPTIONS
325	EnginesReader.Unlock();
326
327	// now that the engines (might) have left fx send signals for master
328	// effects, render all master effects
329	{
330	std::vector<EffectChain*>::iterator iterChains = vEffectChains.begin();
331	std::vector<EffectChain*>::iterator end = vEffectChains.end();
332	for (; iterChains != end; ++iterChains) {
333	if (!(*iterChains)->EffectCount()) continue;
334	(*iterChains)->RenderAudio(Samples);
335	// mix the result of the last effect in the chain to the audio
336	// output device channel(s)
337	Effect* pLastEffect =
338	(iterChains)->GetEffect((iterChains)->EffectCount() - 1);
339	for (int iChan = 0; iChan < pLastEffect->OutputChannelCount() && iChan < ChannelCount(); ++iChan)
340	pLastEffect->OutputChannel(iChan)->MixTo(Channel(iChan), Samples);
341	}
342	}
343
344	return result;
345	}
346
347	int AudioOutputDevice::RenderSilence(uint Samples) {
348	if (Channels.empty()) return 0;
349
350	// reset all channels with silence
351	{
352	std::vector<AudioChannel*>::iterator iterChannels = Channels.begin();
353	std::vector<AudioChannel*>::iterator end = Channels.end();
354	for (; iterChannels != end; iterChannels++)
355	(*iterChannels)->Clear(); // zero out audio buffer
356	}
357
358	return 0;
359	}
360
361	} // namespace LinuxSampler