BUG - juce_AudioUnitPluginFormat.mm

[peteatjuce]

Hi JUCE devs,

I’m working on an audio plug-in host using Juce, and I’ve found a distinct problem with hosting on iOS.

The app’s transport control starts/stops the hosted plug-ins at various times.

It does this by calling prepareToPlay() on each plug-in in response to start events in the UI.

That calls releaseResources() in the plug-in.

That in turn calls AudioUnitReset (audioUnit, kAudioUnitScope_Global, 0);

That in turn seems to lose the plug-in callbacks - so on 2nd playback and later, the Audio Unit stops responding!

My fix was to do this:

    void prepareToPlay (double newSampleRate, int estimatedSamplesPerBlock) override
    {
        if (audioUnit != nullptr)
        {
            releaseResources();

            createPluginCallbacks(); // MPC added!

… that restores the callbacks, and the AudioUnit now works on 2nd and subsequent playbacks.

This looks like a clear bug to me. Am I missing something?!

Best wishes to all,

Pete

[ed95]

Thanks for the report. It looks like some AUs will remove the host callbacks when being uninitialised or reset so we need to re-add them in prepareToPlay(). We don’t want to re-add the parameter listeners on macOS though so the createPluginCallbacks() call needs to be modified a bit to split out the callback/listener logic.

We’ve got a fix for this that will go onto develop after the 6.1.1 bugfix release.

[peteatjuce]

Fabulous, @ed95 ! Looking forward to seeing the patch.

Best wishes, Pete

[ed95]

This is on develop now:

AU: Reset plug-in host callbacks in prepareToPlay() in case they were removed when uninitialising or resetting the audio unit

[peteatjuce]

Thanks @ed95 !

With many thanks to the JUCE team - Wotja 22 is going to be a great release.

Best wishes,

Pete

[peteatjuce]

Dear Juce Devs (@ed95)

Thanks to one of one Beta testers, we’ve found a pretty serious bug in your patch for this issue.
It happens when a hosted AUv3 tries to use the “AU Clock” for timing events

Example:

1. Use hosted miRack AUv3 - set-up trivial patch connecting “CLOCK” to “TRIG” input on Mutable Instrument’s Macro Oscillator 2.
2. Start playback from host - all is good
3. Stop playback from host
4. Re-start playback on host - miRack doesn’t generate notes; timings are missing somehow

NB: any other configurations / plug-ins that don’t rely on (host) AU Clock, things all play fine

Solution: patch juce_AudioUnitPluginFormat.mm as per the attached update.

Best wishes,

Pete

    void prepareToPlay (double newSampleRate, int estimatedSamplesPerBlock) override
    {
        if (audioUnit != nullptr)
        {
            releaseResources();

            // MARK: MPC this is in the RIGHT PLACE (begin)
            // See https://forum.juce.com/t/bug-juce-audiounitpluginformat-mm/47638
            setPluginCallbacks();
            // MARK: MPC this is in the RIGHT PLACE (end)

            for (int dir = 0; dir < 2; ++dir)
            {
                const bool isInput = (dir == 0);
                const AudioUnitScope scope = isInput ? kAudioUnitScope_Input : kAudioUnitScope_Output;
                const int n = getBusCount (isInput);

                for (int i = 0; i < n; ++i)
                {
                    Float64 sampleRate;
                    UInt32 sampleRateSize = sizeof (sampleRate);
                    const Float64 sr = newSampleRate;

                    AudioUnitGetProperty (audioUnit, kAudioUnitProperty_SampleRate, scope, static_cast<UInt32> (i), &sampleRate, &sampleRateSize);

                    if (sampleRate != sr)
                    {
                        if (isAUv3) // setting kAudioUnitProperty_SampleRate fails on AUv3s
                        {
                            AudioStreamBasicDescription stream;
                            UInt32 dataSize = sizeof (stream);
                            auto err = AudioUnitGetProperty (audioUnit, kAudioUnitProperty_StreamFormat, scope, static_cast<UInt32> (i), &stream, &dataSize);

                            if (err == noErr && dataSize == sizeof (stream))
                            {
                                stream.mSampleRate = sr;
                                AudioUnitSetProperty (audioUnit, kAudioUnitProperty_StreamFormat, scope, static_cast<UInt32> (i), &stream, sizeof (stream));
                            }
                        }
                        else
                        {
                            AudioUnitSetProperty (audioUnit, kAudioUnitProperty_SampleRate, scope, static_cast<UInt32> (i), &sr, sizeof (sr));
                        }
                    }

                    if (isInput)
                    {
                        AURenderCallbackStruct info;
                        zerostruct (info); // (can't use "= { 0 }" on this object because it's typedef'ed as a C struct)

                        info.inputProcRefCon = this;
                        info.inputProc = renderGetInputCallback;

                        AudioUnitSetProperty (audioUnit, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Input,
                                              static_cast<UInt32> (i), &info, sizeof (info));
                    }
                    else
                    {
                        outputBufferList.add (new AUBuffer (static_cast<size_t> (getChannelCountOfBus (false, i))));
                    }
                }
            }

            UInt32 frameSize = (UInt32) estimatedSamplesPerBlock;
            AudioUnitSetProperty (audioUnit, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, 0,
                                  &frameSize, sizeof (frameSize));

            setRateAndBufferSizeDetails ((double) newSampleRate, estimatedSamplesPerBlock);

            updateLatency();

            zerostruct (timeStamp);
            timeStamp.mSampleTime = 0;
            timeStamp.mHostTime = GetCurrentHostTime (0, newSampleRate, isAUv3);
            timeStamp.mFlags = kAudioTimeStampSampleTimeValid | kAudioTimeStampHostTimeValid;

            currentBuffer = nullptr;
            wasPlaying = false;

            resetBuses();

            bool ignore;

            if (! syncBusLayouts (getBusesLayout(), false, ignore))
                return;

            prepared = (AudioUnitInitialize (audioUnit) == noErr);

            if (prepared)
            {
                if (! haveParameterList)
                    refreshParameterList();

                // MARK: MPC this is in the WRONG PLACE (begin)
                // See https://forum.juce.com/t/bug-juce-audiounitpluginformat-mm/47638
                //setPluginCallbacks();
                // MARK: MPC this is in the WRONG PLACE (end)


                if (! syncBusLayouts (getBusesLayout(), true, ignore))
                {
                    prepared = false;
                    AudioUnitUninitialize (audioUnit);
                }
            }
        }
    }

[ed95]

Thanks Pete, this change is on develop now:

AU: Set plug-in host callbacks immediately after calling releaseResources() in prepareToPlay() in case the audio unit relies on them during initialisation

[peteatjuce]

Hi @ed95 great stuff, thanks for letting me know!

Best wishes, Pete