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POAudioUnit set property error (error code -10868)
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copied!<p>I am trying to set a property in AudioUnit using AudioStreamBasicDescription. I am trying to set the format for the sound data. The error code returned is -10868. It only occurs on iOS 3.1.3 or less, but works on 3.2 or up. So it works in the simulator, on an iPod touch running 4.2, but not a 1st gen iPod touch.</p> <p>The error occurs when I try to set the format for the AudioUnit tone unit. The code looks like this (and is from <a href="http://cocoawithlove.com/2010/10/ios-tone-generator-introduction-to.html" rel="nofollow">cocoawithlove.com</a>)</p> <pre><code>// Set the format to 32 bit, single channel, floating point, linear PCM const int four_bytes_per_float = 4; const int eight_bits_per_byte = 8; AudioStreamBasicDescription streamFormat; streamFormat.mSampleRate = sampleRate; streamFormat.mFormatID = kAudioFormatLinearPCM; streamFormat.mFormatFlags = kAudioFormatFlagsNativeFloatPacked | kAudioFormatFlagIsNonInterleaved; streamFormat.mBytesPerPacket = four_bytes_per_float; streamFormat.mFramesPerPacket = 1; streamFormat.mBytesPerFrame = four_bytes_per_float; streamFormat.mChannelsPerFrame = 1; streamFormat.mBitsPerChannel = four_bytes_per_float * eight_bits_per_byte; err = AudioUnitSetProperty (toneUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &streamFormat, sizeof(AudioStreamBasicDescription)); // err now has error code -10868 </code></pre> <p>I checked around in headers and this error code corresponds to the error "kAudioUnitErr_FormatNotSupported". So I guess the format I'm trying to set is not supported on iOS 3.1? Where can I find supported formats? Any pointers on other formats I could try out?</p> <p>The render callback used:</p> <pre><code>OSStatus RenderTone( void *inRefCon, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData) { // Fixed amplitude is good enough for our purposes const double amplitude = 0.25; // Get the tone parameters out of the view controller ToneGeneratorViewController *viewController = (ToneGeneratorViewController *)inRefCon; double theta = viewController->theta; double theta_increment = 2.0 * M_PI * viewController->frequency / viewController->sampleRate; // This is a mono tone generator so we only need the first buffer const int channel = 0; Float32 *buffer = (Float32 *)ioData->mBuffers[channel].mData; // Generate the samples for (UInt32 frame = 0; frame < inNumberFrames; frame++) { buffer[frame] = sin(theta) * amplitude; theta += theta_increment; if (theta > 2.0 * M_PI) { theta -= 2.0 * M_PI; } } // Store the updated theta back in the view controller viewController->theta = theta; return noErr; } </code></pre>

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