If you are grabbing the FLV that's all digital and will not lose quality. However you will find that players render this with varying quality. Of course you want to try VLC PLAYER.
I have the DownloadHelper in Mozilla and Internet Explorer. With
that extension I can download *.flv videos from a web (not youtube). But
I discovered that when I play the video that I downloaded, the quality
is not the same as the original video. I lose quality. The only way to
download the videos that I want is via DownloadHelper. I tried with the
convert option to different formats and I cant get the same quality as
in the original web page. Why? I dont know. Maybe is a codec thing? or I
need to do something special? please give me your opinion. Thank you.