that depends:
- ffmpeg is LGPL. LGPL is good.
- FFmpeg License and Legal Considerations
- x264 may require a license for some forms of commercial use but you can build ffmpeg without it
- [x264-devel] Announcing commercial licensing for x264
- gstreamer would have the same patent issues as ffmpeg but OpenCV has better support for ffmpeg
I don’t see you mentioning what codecs you’ll use…