I'm trying to get a sample to trigger on the beat.
When I hit play, from 1:1 in AU Lab, with the following code the first beat fails to play.
if (pstore.value[p::master_autoplay] == 1.0f) {
AudioPlayHead::CurrentPositionInfo cpi;
playhead->getCurrentPosition(cpi);
// Get the current position information from the playhead.
// Calcuate how many samples per beat, divide the current time in samples
// by the samplesPerBeat.
// This gets us the number of samples we are past the last beat.
// In the processing loop, later, we increment
// offsetFromLastBeat as we process the sample.
// And, if it reaches samplesPerBeat return to 0
// And, if it's zero play a beat.
if (cpi.isPlaying || cpi.isRecording) {
samplesPerBeat = sr * (60.0 / cpi.bpm); // BREAKPOINT
if (samplesPerBeat != 0.0) {
offsetFromLastBeat = cpi.timeInSamples % samplesPerBeat;
}
} else {
offsetFromLastBeat = -1; // do not auto play if sequencer stopped
}
}
When I hit play in AU Lab with a breakpoint set at BREAKPOINT the value of timeInSamples is already above 0. So my first beat fails to trigger. I presume that's because it's already processing a block.
Now I can hack this to work by looking for when the playback has started half way through an existing sample block and playing a beat fractionally late. But is this the best way of tackling it at all?
I'm presuming that as the documentation states: "getCurrentPosition(...): Fills-in the given structure with details about the transport's position at the start of the current processing block." there's no point in calling getCurrentPosition continuously for an update!
It works fine in Ableton. I presume that only starts playing at the beginning of a block.
thoughts? Are all other sequencers as well behaved as Ableton and is AU Lab an unfair test?