#4209 Select at least one A/V source

This error means you haven't selected any audio or video file to process.

Solution:

1. Click the "Select Audio/Video" button on the main interface.
2. Browse and select one or more video/audio files (hold Ctrl for multiple selection).
3. If you want to batch process all files in a folder, check the "Folder" checkbox instead.

After selecting, click the "Start" button to begin processing.

Please refer to the relevant documentation:

• Quick Start - pyVideoTrans
• Video Translation Core Function