I am using a 14-day trial of
Machete Pro (it would cost $20 to buy). It says it is a "lossless" video editor so you don't lose quality. It is quite easy to use, with icons to find last/next key frame, which is necessary (I understand) with flv - you don't need to with wmv, which is the other format I've used it for.
There is a free version, Machete Lite, but it only does wma and avi.
http://www.machetesoft.com/home/about-machete.html
Another very user-friendly flv editor is
Freemake Video Converter - but there's a snag - edited files can only be converted (to lots of formats) or uploaded to YouTube, you cannot simply save them to disk when you've finished clipping, you have to convert them first. Machete does do that. Having both of them is a good idea, I'm beginning to think. Freemake is freeware.
http://www.freemake.com/free_video_converter/
I am not experienced, so I hope I have understood your needs correctly. I would think that if I can use those two programs, anyone can
clemenzina
