Hi, I am not sure that it is possible to enter into mencoder/ffmpeg (havent found) the output final size. I would need 650 mb to burn a video from my camera.

Thank you

There is a -filesize <limit> option for ffmpeg. This stops transcoding when the limit is reached. You might want to try different bitrates and get an idea how much each uses per minute of video. Then add the -filesize opton as a hard limit.

It will stop thus after a given size, and leave unfinished video.
Let's say when we would like to convert a WMV/MP3 to MP4/MP3 with a total file size of 650mb, and ffmpeg/mencoder adapts itself automatically the frames ?

You said that the source was a camera, so I didn't know you that you are dealing with fixed sized video. The bitrate of the video will make up the bulk of the file, so if you limit the maximum bitrate of the video, the output video will be less than 650 MB.

You can produce a fixed rate video or control the bitrate tolerence, to make your calculation easier.

I seem to remember being able to control the bitrate via a feedback mechanism while the transcoder is running. I don't remember which program. It might have been transcode.