Hello, i have an issue here. so, when i try to play the preview, the audio played smoothly and the red line move smoothly too through the layer, but the preview video doesn't play at all. what should i do??
Try lowering the resolution factor from Full to Quarter. Try lowering the resolution factor from Full to Quarter. And disable Motion Blur while you are working on compositing (the three balls that in your screenshot are in blue on the timeline). Also, remember that After Effects first makes a reading of everything that is happening in your timeline and stores it in RAM (green line), after that you will be able to see everything in real time as far as the green line or your RAM has reached.