ive me a picture of the digital avatar structure at the system level, it is the pipeline, from the user speaking, and use stt model to convert audio to text, then input to the chatgpt, get the response from chatgpt, use tts to convert text to the audio. And use the wave to lip to generate the video from the audio. Finally, output a video response as a digital avatar. Try to be simple and clear. and do not include any irrelevant component. Try to be as simple as possible. And note that this is a poster of the technical report, so try to be clear, not too fancy