Hi,
1) cut the actual stream file with the following command
e:\ffmpeg\bin\ffmpeg -ss 0:1:0 -i C:\VideoFiles\streamfile.flv -t 0:1:5 C:\VideoFiles\output.flv
here, 0:1:0 (hh:mm:ss) & same as for 0:1:5
repeat the same for all the streams
2) extract the audio streams form (n-1) streams using the following
e:\ffmpeg\bin\ffmpeg -i C:\VideoFiles\output.flv -vn -ar 44100 -ac 2 -ab 192 -f mp3 C:\VideoFiles\output.mp3
repeat for all the other streams
3) mix all outcomes into one audio file using the following
e:\ffmpeg\bin\ffmpeg -i C:\VideoFiles\out1.mp3 C:\VideoFiles\out2.mp3 C:\VideoFiles\MERGE_FILE.mp3
and combine the all output files in to one using the following command
4) append the final audio + video file using the following
e:\ffmpeg\bin\ffmpeg -i C:\VideoFiles\MERGE_FILE.mp4 -i C:\VideoFiles\MERGE_FILE.mp3 -ar 44100 C:\VideoFiles\finaloutput.mp4