#7278 Video file selection required

This means the software has no video file loaded — you clicked "Start" without first selecting an audio/video file (or the selected file was invalid/removed).

Fix:

1. Click the top-left Select audio or video button and choose your mp4/mkv/avi/mov/wav/mp3 file.
2. If you want to batch process, check the Folder checkbox instead and select the folder.
3. Confirm the file name/path contains only English letters, numbers and underscores — no Chinese characters, spaces, or special symbols. Your path D:/Program file/win-pyvideotrans-v4.12-0908 contains a space in Program file, which is known to cause loading failures. Move the app to a shallow, space-free path such as D:/pyVideoTrans.
4. Restart the software and select the video again, then click Start.

Please refer to the related documentation:

• First use quick start
• Getting started