How to parallelly process multiple outputs for the same one input timestamp?

I'm implementing 2 calculators for TTS (Text To Speech) and Audio2Face (both are real-time stream web socket APIs). Firstly TTSCalculator has a long text input, and it may successively output multiple audio clips, then each audio clip should be immediately converted to face blendshapes in Audio2FaceCalculator.

Currently MediaPipe Scheduler seems begin to process the first audio clip (in the 2nd graph node) only if all the audio clips are output (in the first graph node), instead of processing an audio clip immediately after produced one.

How can I process an audio clip in the 2nd node immediately after produced one in the first node?