[Ffmpeg-devel] concatenate 2

[Jim Shupert, Jr.]

attempting to concatennate several mpg programstreams ( on a win xp w ffmpeg )
if I use the syntax

cat j1.mpg j2.mpg j3.mpg j4.mpg | ffmpeg -i - -acodec copy -vcodec copy jjjj.mpg

where i have 4 program streams  j1.mpg , j2.mpg, j3.mpg j4.mpg   and I wish to cat them into 1 mpg program stream jjjj.mpg

I get a whole lot of text flying in the command shell  then a pipe :: Unknown format

Can I use ffmpeg to cat files?   am I doing something wrong?  and if so - what?

thanks

jims