Hello,

I'm trying to synchronizing the buffer in a scriptProcessorNode with native/regular web audio nodes and I'm having some problems. My problem is that I want to synchronize the scriptProcessorNode with a ramp of a GainNode.

My program looks like the attached diagram. Each scriptProcessorNode is a filter with n coefficients and these coefficients are in a global variable. My problem comes when I try to update these coefficients and do a ramp in the gain through an audioParam at the "same time".

The start scenario is (in pseudo-code):

audioBufferSourceNode.connect(scriptProcessorNode0);

audioBufferSourceNode.connect(scriptProcessorNode1);

scriptProcessorNode0.connect(gainNode0);

scriptProcessorNode0.connect(gainNode1);

gainNode0.connect(audioContext.destination);

gainNode1.connect(audioContext.destination);

gainNode1.gain.value = 0;

globalVariableOfCoefficients0 = coefficients0;

globalVariableOfCoefficients1 = null;

audioBufferSourceNode.start(0);

The reason to have two scriptProcessorNodes is because I want to do a smooth transition of the coefficients, so I do a crossfading between the 'old' coefficients (scriptProcessorNode0) and the 'new' coefficients (scriptProcessorNode1) with the ramps of gainNode0 and gainNode1. So when I receive the notification to update the coefficients, the global variable is updated and the ramps are started.

The first problem is that when I change the globalVariableOfCoefficients1, I don't know if the value of the variable is really updated in the scriptProcessorNode. It seems that the scriptProcessorNode have to wait until get a new buffer to update the value of their global variables . On the other hand, there a second problem. If I change the value of the globalVariableOfCoefficients1 and I wait to get a new buffer for update their global variables, how I can know when the first sample of this new buffer "is" really in the gainNode? 

On the other hand, I would like to find some documentation where the relation between the scriptProcessorNode and the audio thread  is explained for clearly understand the problematic.

Thank you very much in advance,