This the only free solution to watermark video files. MPEG Streamclip is a powerful high-quality video converter, player, editor for MPEG, QuickTime, transport streams, iPod. And now it is a DivX editor and encoding machine, and even a movie downloader.
MPEG Streamclip (link) : Apply Watermarks on Videos
You can use MPEG Streamclip to: open and play most movie formats including MPEG files or transport streams; edit them with Cut, Copy, Paste, and Trim; set In/Out points and convert them into muxed or demuxed files, or export them to QuickTime, AVI, DV and MPEG-4 files with more than professional quality, so you can easily import them in a DVD authoring tool, and use them with many other applications or devices.Supported input formats: MPEG, VOB, PS, M2P, MOD,VRO, DAT, MOV, DV, AVI, MP4, TS, M2T, MMV, REC, VID, AUD, AVR, VDR, PVR, TP0, M2V, M1V, MPV, AIFF, M1A, MP2, MPA, AC3, …
- Open video file in MPEG Streamclip.
- Go to Files >> Export to Avi.
- A new window pops up. Click Adjustments at the lower-right of the box.
- Enter some text in the Watermark textbox. Click Ok and hit ‘Make avi’ button.