Can anyone share their preferred method for adding watermarks before uploading to video share sites such as YouTube? It would be a lot easier for me if we can do FLV-to-FLV, without going to upstream video source files. Also, a command line batch program would be a big time saver.
The trouble with going from flv to flv is you'll need to recompress the data, it's just like images and every recompresssion takes a little more out of the original video.
I don't use flv so I,m not familiar with the tools for it. Most higher end consumer apps like Video Studio. should be able to do this with standard video. For free and with batch capability Virtual dub will fit the bill but I'm pretty sure it's not going to accept .flv but I may be mistaken. Haven't looked in many years and back in the day MPEG support had just arrived.
You should be able t embed a transparent PNG or Tiff into your video software and then re-render it as an FLV ... this is how I do it with my tools.. Currently I used Sony Vegas and now I use Adobe CS4
Recently I needed this functionality, too, and found that ffmpeg (free software) can do this. It mainly comes uncompiled but there are precompiled Windows versions. Use some SE to find "ffmpeg win32 builds". Choose a version that includes "VHooks".
Detailed docs are available on the ffmpeg site. Basic command to add watermark image sampleimage.jpg to your samplevideo.avi: