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Code Activity

iOS Audio: Add waiting mechanism after AVAudioSession setActive: to ensure correct buffer size detection on iOS 18

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The waiting is only added on iOS 18 as this is the only platform where
seems to be an asynchronous relationship between
(1) AVAudioSession setActive:
(2) AVAudioSession setPreferredIOBufferDuration:
and (3) AVAudioSession.IOBufferDuration.

The issue is not observable in the iOS 18 emulator.
This commit is contained in:
attila 2024-10-01 16:50:50 +02:00 • committed by reuk
parent d3e254e24f
commit 70c9c5bfdb
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GPG key ID: FCB43929F012EE5C
1 changed files with 101 additions and 6 deletions
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107
modules/juce_audio_devices/native/juce_Audio_ios.cpp
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@ -257,6 +257,81 @@ private:
JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (iOSAudioIODeviceType)
};
class SubstituteAudioUnit
{
public:
/* Returns true if the audio callback was called. False if a timeout occurred. */
bool waitForAudioCallback()
{
if (audioUnit != nullptr)
{
AudioComponentInstanceDispose (audioUnit);
audioUnit = nullptr;
}
AudioComponentDescription desc;
desc.componentType = kAudioUnitType_Output;
desc.componentSubType = kAudioUnitSubType_RemoteIO;
desc.componentManufacturer = kAudioUnitManufacturer_Apple;
desc.componentFlags = 0;
desc.componentFlagsMask = 0;
AudioComponent comp = AudioComponentFindNext (nullptr, &desc);
AudioComponentInstanceNew (comp, &audioUnit);
if (audioUnit == nullptr)
return false;
{
AURenderCallbackStruct inputProc;
inputProc.inputProc = audioUnitCallback;
inputProc.inputProcRefCon = this;
AudioUnitSetProperty (audioUnit, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Input, 0, &inputProc, sizeof (inputProc));
}
{
AudioStreamBasicDescription format;
zerostruct (format);
format.mSampleRate = [AVAudioSession sharedInstance].sampleRate;
format.mFormatID = kAudioFormatLinearPCM;
format.mFormatFlags = kAudioFormatFlagIsFloat | kAudioFormatFlagIsNonInterleaved | kAudioFormatFlagsNativeEndian | kLinearPCMFormatFlagIsPacked;
format.mBitsPerChannel = 8 * sizeof (float);
format.mFramesPerPacket = 1;
format.mChannelsPerFrame = 2;
format.mBytesPerFrame = format.mBytesPerPacket = sizeof (float);
AudioUnitSetProperty (audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &format, sizeof (format));
AudioUnitSetProperty (audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &format, sizeof (format));
}
AudioUnitInitialize (audioUnit);
AudioOutputUnitStart (audioUnit);
const auto result = audioCallbackOccurred.wait (1000.0);
AudioComponentInstanceDispose (audioUnit);
audioUnit = nullptr;
return result;
}
private:
static OSStatus audioUnitCallback (void* object,
AudioUnitRenderActionFlags*,
const AudioTimeStamp*,
UInt32,
UInt32,
AudioBufferList*)
{
static_cast<SubstituteAudioUnit*> (object)->audioCallbackOccurred.signal();
return noErr;
}
AudioUnit audioUnit{};
WaitableEvent audioCallbackOccurred;
};
//==============================================================================
struct iOSAudioIODevice::Pimpl final : public AsyncUpdater
{
@ -311,6 +386,16 @@ struct iOSAudioIODevice::Pimpl final : public AsyncUpdater
{
JUCE_NSERROR_CHECK ([[AVAudioSession sharedInstance] setActive: enabled
error: &error]);
if (@available (ios 18, *))
{
if (enabled)
{
SubstituteAudioUnit au;
[[maybe_unused]] const auto success = au.waitForAudioCallback();
jassert (success);
}
}
}
int getBufferSize (const double currentSampleRate)
@ -334,8 +419,20 @@ struct iOSAudioIODevice::Pimpl final : public AsyncUpdater
NSTimeInterval bufferDuration = currentSampleRate > 0 ? (NSTimeInterval) (newBufferSize + extraOffset) / currentSampleRate : 0.0;
auto session = [AVAudioSession sharedInstance];
JUCE_NSERROR_CHECK ([session setPreferredIOBufferDuration: bufferDuration
error: &error]);
// According to the apple docs, it's best to set preferred sample rates and block sizes
// while the device is inactive, and then to query the real values after activation.
// Unfortunately, on iOS 18.0, the real block size isn't immediately available after
// a call to setActive, so we also need to wait for the first audio callback.
// This will be slow!
// https://developer.apple.com/library/archive/qa/qa1631/_index.html
if (@available (ios 18, *))
setAudioSessionActive (false);
JUCE_NSERROR_CHECK ([session setPreferredIOBufferDuration: bufferDuration error: &error]);
if (@available (ios 18, *))
setAudioSessionActive (true);
return getBufferSize (currentSampleRate);
}
@ -347,7 +444,7 @@ struct iOSAudioIODevice::Pimpl final : public AsyncUpdater
auto newBufferSize = tryBufferSize (sampleRate, 64);
jassert (newBufferSize > 0);
const auto longestBufferSize = tryBufferSize (sampleRate, 4096);
const auto longestBufferSize = tryBufferSize (sampleRate, 4096);
while (newBufferSize <= longestBufferSize)
{
@ -377,9 +474,7 @@ struct iOSAudioIODevice::Pimpl final : public AsyncUpdater
double trySampleRate (double rate)
{
auto session = [AVAudioSession sharedInstance];
JUCE_NSERROR_CHECK ([session setPreferredSampleRate: rate
error: &error]);
JUCE_NSERROR_CHECK ([session setPreferredSampleRate: rate error: &error]);
return session.sampleRate;
}