Je cherche un exemple d'utilisation des services de file d'attente audio. Je voudrais créer un son en utilisant une équation mathématique, puis l'entendre.Exemple d'utilisation de services de files d'attente audio
Voici mon code pour générer du son à partir d'une fonction. Je suppose que vous savez comment utiliser les services AudioQueue, configurer une session audio et démarrer et arrêter correctement une file d'attente de sortie audio.
Voici un extrait pour la mise en place et le démarrage d'une AudioQueue de sortie:
// Get the preferred sample rate (8,000 Hz on iPhone, 44,100 Hz on iPod touch)
size = sizeof(sampleRate);
err = AudioSessionGetProperty (kAudioSessionProperty_CurrentHardwareSampleRate, &size, &sampleRate);
if (err != noErr) NSLog(@"AudioSessionGetProperty(kAudioSessionProperty_CurrentHardwareSampleRate) error: %d", err);
//NSLog (@"Current hardware sample rate: %1.0f", sampleRate);
BOOL isHighSampleRate = (sampleRate > 16000);
int bufferByteSize;
AudioQueueBufferRef buffer;
// Set up stream format fields
AudioStreamBasicDescription streamFormat;
streamFormat.mSampleRate = sampleRate;
streamFormat.mFormatID = kAudioFormatLinearPCM;
streamFormat.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger | kLinearPCMFormatFlagIsPacked;
streamFormat.mBitsPerChannel = 16;
streamFormat.mChannelsPerFrame = 1;
streamFormat.mBytesPerPacket = 2 * streamFormat.mChannelsPerFrame;
streamFormat.mBytesPerFrame = 2 * streamFormat.mChannelsPerFrame;
streamFormat.mFramesPerPacket = 1;
streamFormat.mReserved = 0;
// New output queue ---- PLAYBACK ----
if (isPlaying == NO) {
err = AudioQueueNewOutput (&streamFormat, AudioEngineOutputBufferCallback, self, nil, nil, 0, &outputQueue);
if (err != noErr) NSLog(@"AudioQueueNewOutput() error: %d", err);
// Enqueue buffers
//outputFrequency = 0.0;
outputBuffersToRewrite = 3;
bufferByteSize = (sampleRate > 16000)? 2176 : 512; // 40.5 Hz : 31.25 Hz
for (i=0; i<3; i++) {
err = AudioQueueAllocateBuffer (outputQueue, bufferByteSize, &buffer);
if (err == noErr) {
[self generateTone: buffer];
err = AudioQueueEnqueueBuffer (outputQueue, buffer, 0, nil);
if (err != noErr) NSLog(@"AudioQueueEnqueueBuffer() error: %d", err);
} else {
NSLog(@"AudioQueueAllocateBuffer() error: %d", err);
return;
}
}
// Start playback
isPlaying = YES;
err = AudioQueueStart(outputQueue, nil);
if (err != noErr) { NSLog(@"AudioQueueStart() error: %d", err); isPlaying= NO; return; }
} else {
NSLog (@"Error: audio is already playing back.");
}
Voici la partie qui génère le ton:
// AudioQueue output queue callback.
void AudioEngineOutputBufferCallback (void *inUserData, AudioQueueRef inAQ, AudioQueueBufferRef inBuffer) {
AudioEngine *engine = (AudioEngine*) inUserData;
[engine processOutputBuffer:inBuffer queue:inAQ];
}
- (void) processOutputBuffer: (AudioQueueBufferRef) buffer queue:(AudioQueueRef) queue {
OSStatus err;
if (isPlaying == YES) {
[outputLock lock];
if (outputBuffersToRewrite > 0) {
outputBuffersToRewrite--;
[self generateTone:buffer];
}
err = AudioQueueEnqueueBuffer(queue, buffer, 0, NULL);
if (err == 560030580) { // Queue is not active due to Music being started or other reasons
isPlaying = NO;
} else if (err != noErr) {
NSLog(@"AudioQueueEnqueueBuffer() error %d", err);
}
[outputLock unlock];
} else {
err = AudioQueueStop (queue, NO);
if (err != noErr) NSLog(@"AudioQueueStop() error: %d", err);
}
}
-(void) generateTone: (AudioQueueBufferRef) buffer {
if (outputFrequency == 0.0) {
memset(buffer->mAudioData, 0, buffer->mAudioDataBytesCapacity);
buffer->mAudioDataByteSize = buffer->mAudioDataBytesCapacity;
} else {
// Make the buffer length a multiple of the wavelength for the output frequency.
int sampleCount = buffer->mAudioDataBytesCapacity/sizeof (SInt16);
double bufferLength = sampleCount;
double wavelength = sampleRate/outputFrequency;
double repetitions = floor (bufferLength/wavelength);
if (repetitions > 0.0) {
sampleCount = round (wavelength * repetitions);
}
double x, y;
double sd = 1.0/sampleRate;
double amp = 0.9;
double max16bit = SHRT_MAX;
int i;
SInt16 *p = buffer->mAudioData;
for (i = 0; i < sampleCount; i++) {
x = i * sd * outputFrequency;
switch (outputWaveform) {
case kSine:
y = sin (x * 2.0 * M_PI);
break;
case kTriangle:
x = fmod (x, 1.0);
if (x < 0.25)
y = x * 4.0; // up 0.0 to 1.0
else if (x < 0.75)
y = (1.0 - x) * 4.0 - 2.0; // down 1.0 to -1.0
else
y = (x - 1.0) * 4.0; // up -1.0 to 0.0
break;
case kSawtooth:
y = 0.8 - fmod (x, 1.0) * 1.8;
break;
case kSquare:
y = (fmod(x, 1.0) < 0.5)? 0.7: -0.7;
break;
default: y = 0; break;
}
p[i] = y * max16bit * amp;
}
buffer->mAudioDataByteSize = sampleCount * sizeof (SInt16);
}
}
Quelque chose à surveiller est que votre rappel sera appelé sur un thread non principal, vous devez donc pratiquer la sécurité des threads avec des verrous, des mutex ou d'autres techniques.
Niveau élevé: utiliser AVAudioPlayer https://github.com/hollance/AVBufferPlayer
niveau Med: les files d'attente audio trailsinthesand.com/exploring-iphone-audio-part-1/ vous fait aller bien. NOTE: J'ai enlevé le http pour que l'ancien lien puisse être là, mais il dirige directement vers un mauvais site, donc il a apparemment changé.
Niveau bas: Vous pouvez descendre un niveau et de le faire avec des unités audio: http://cocoawithlove.com/2010/10/ios-tone-generator-introduction-to.html
Ceci est une version utilisant C# du même échantillon de @lucius
void SetupAudio()
{
AudioSession.Initialize();
AudioSession.Category = AudioSessionCategory.MediaPlayback;
sampleRate = AudioSession.CurrentHardwareSampleRate;
var format = new AudioStreamBasicDescription() {
SampleRate = sampleRate,
Format = AudioFormatType.LinearPCM,
FormatFlags = AudioFormatFlags.LinearPCMIsSignedInteger | AudioFormatFlags.LinearPCMIsPacked,
BitsPerChannel = 16,
ChannelsPerFrame = 1,
BytesPerFrame = 2,
BytesPerPacket = 2,
FramesPerPacket = 1,
};
var queue = new OutputAudioQueue (format);
var bufferByteSize = (sampleRate > 16000)? 2176 : 512; // 40.5 Hz : 31.25 Hz
var buffers = new AudioQueueBuffer* [numBuffers];
for (int i = 0; i < numBuffers; i++){
queue.AllocateBuffer (bufferByteSize, out buffers [i]);
GenerateTone (buffers [i]);
queue.EnqueueBuffer (buffers [i], null);
}
queue.OutputCompleted += (object sender, OutputCompletedEventArgs e) => {
queue.EnqueueBuffer (e.UnsafeBuffer, null);
};
queue.Start();
return true;
}
C'est le générateur de sons:
void GenerateTone (AudioQueueBuffer *buffer)
{
// Make the buffer length a multiple of the wavelength for the output frequency.
uint sampleCount = buffer->AudioDataBytesCapacity/2;
double bufferLength = sampleCount;
double wavelength = sampleRate/outputFrequency;
double repetitions = Math.Floor (bufferLength/wavelength);
if (repetitions > 0)
sampleCount = (uint)Math.Round (wavelength * repetitions);
double x, y;
double sd = 1.0/sampleRate;
double amp = 0.9;
double max16bit = Int16.MaxValue;
int i;
short *p = (short *) buffer->AudioData;
for (i = 0; i < sampleCount; i++) {
x = i * sd * outputFrequency;
switch (outputWaveForm) {
case WaveForm.Sine:
y = Math.Sin (x * 2.0 * Math.PI);
break;
case WaveForm.Triangle:
x = x % 1.0;
if (x < 0.25)
y = x * 4.0; // up 0.0 to 1.0
else if (x < 0.75)
y = (1.0 - x) * 4.0 - 2.0; // down 1.0 to -1.0
else
y = (x - 1.0) * 4.0; // up -1.0 to 0.0
break;
case WaveForm.Sawtooth:
y = 0.8 - (x % 1.0) * 1.8;
break;
case WaveForm.Square:
y = ((x % 1.0) < 0.5)? 0.7: -0.7;
break;
default: y = 0; break;
}
p[i] = (short)(y * max16bit * amp);
}
buffer->AudioDataByteSize = sampleCount * 2;
}
}
Vous voulez aussi ces définitions:
enum WaveForm {
Sine, Triangle, Sawtooth, Square
}
WaveForm outputWaveForm;
const float outputFrequency = 220;
pouvez-vous partager votre code? –