How to lossless convert FLV to MP4 with ffmpeg?

How can I lossless convert an *.flv video to *.mp4 container ?
At first I thought the following will do the job:

ffmpeg -i sss.flv -vcodec copy -acodec copy ttt.mp4

but when i do this I get the following error:


[NULL @ 000000000206c560] Unable to find a suitable output format for 'D:\tmp\ttt.mp4)'
D:\tmp\ttt.mp4): Invalid argument

Whats wrong?

I am using the newest (static) ffmpeg under 64bit Win7. ffmpeg works fine for other jobs.


Peter