Re: AUMIDISynth program change messages not working?
Re: AUMIDISynth program change messages not working?
- Subject: Re: AUMIDISynth program change messages not working?
- From: Douglas Scott <email@hidden>
- Date: Tue, 12 Jan 2016 09:54:38 -0800
Yes. When “enable preload” is on, sending a program change tells the AU to load the resources for the particular patch from file into memory. The idea is that you do ALL of those “preload” requests up front, before doing anything else. Once “enable preload” is off again, the AU responds like any GM synth does, and responds to program changes as a request switch to the requested (and already pre-loaded) patch during MIDI playback.
-DS
> On Jan 11, 2016, at 12:47 PM, Archagon <email@hidden> wrote:
>
> Hi Douglas, thank you for the help. I had tried playing with
> kAUMIDISynthProperty_EnablePreload before sending my original e-mail,
> but I didn't realize I had to disable it before sending further MIDI
> messages. ("Playback" seemed like it was referring to MusicSequence,
> not real-time MIDI note-on messages.)
>
> This time, I had trouble getting it to work, but then I realized I had
> to send the program change message a second time after enabling
> preload for my chosen instrument:
>
> UInt32 instrument = arc4random_uniform(100);
>
> UInt32 enabled = 1;
> AudioUnitSetProperty(self.samplerUnit,
> kAUMIDISynthProperty_EnablePreload, kAudioUnitScope_Global, 0,
> &enabled, sizeof(enabled));
>
> UInt32 command = 0xC0 | 0;
> MusicDeviceMIDIEvent(self.samplerUnit, command, instrument, 0, 0);
>
> enabled = 0;
> AudioUnitSetProperty(self.samplerUnit,
> kAUMIDISynthProperty_EnablePreload, kAudioUnitScope_Global, 0,
> &enabled, sizeof(enabled));
>
> // sending the program change message a second time!
> MusicDeviceMIDIEvent(self.samplerUnit, command, instrument, 0, 0);
>
> UInt32 noteNum = kMidNote;
> UInt32 onVelocity = 127;
> UInt32 noteCommand = kMIDIMessage_NoteOn << 4 | 0;
> MusicDeviceMIDIEvent(self.samplerUnit, noteCommand, noteNum, onVelocity, 0);
>
> This code finally let me switch the instrument on device. Without the
> second program change message, the synth was stuck on the piano patch.
> Is this the correct approach?
>
> Thank you,
> -Alexei
>
> On Mon, Jan 11, 2016 at 10:14 AM, Douglas Scott <email@hidden> wrote:
>> From AudioUnitProperties.h:
>>
>> /*!
>> @enum Apple AUMIDISynth Property IDs
>> @abstract The collection of property IDs for the Apple Midi Synth audio
>> unit.
>>
>>
>>
>> @discussion The AUMIDISynth audio unit lets a client create fully
>> GM-compatible Midi Synth.
>>
>>
>>
>> @constant kAUMIDISynthProperty_EnablePreload
>> @discussion Scope: Global
>> Value Type: UInt32
>> Access: Write
>>
>>
>>
>> Setting this property to 1 puts the MIDISynth in a mode where it will
>> attempt to load
>> instruments from the bank or file when it receives a program change
>> message. This
>> is used internally by the MusicSequence. It should only be used prior to
>> MIDI playback,
>> and must be set back to 0 before attempting to start playback.
>> */
>>
>> CF_ENUM(AudioUnitPropertyID) {
>> kAUMIDISynthProperty_EnablePreload = 4119
>> };
>>
>> This is needed on the device because we do not have the spare memory to load
>> every instrument from a bank in advance. Set this property to 1, send your
>> program changes (looks like you will need to send a message for ALL of them
>> if you are randomly choosing one later), then set the property to 0, then
>> start playback.
>>
>> -DS
>>
>> On Jan 9, 2016, at 8:00 PM, Archagon <email@hidden> wrote:
>>
>> Hello,
>>
>> I can't figure out how to make the AUMIDISynth MusicDevice
>> (kAudioUnitType_MusicDevice, kAudioUnitSubType_MIDISynth) change its
>> instrument on iOS. In the simulator, sending the following message...
>>
>> UInt32 command = 0xC0 | 0;
>> UInt32 instrument = arc4random_uniform(100);
>> MusicDeviceMIDIEvent(self.samplerUnit, command, instrument, 0, 0);
>>
>> ...works fine. On device, however, the synth just goes mute after
>> receiving the message. (The first instrument in the soundfont —
>> usually piano — does load correctly, however.) Is this a bug? If so,
>> is there any way to work around it?
>>
>> Here's a simple test case based on the LoadPreset demo:
>> https://github.com/archagon/ios-midisynth-program-change-bug-demo
>> You can tap the middle button to change to a random instrument.
>>
>> Thank you,
>> -Alexei
>>
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>
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