windows (ideally .net callable) api join mp4 and/or 3gp files?

i'm operative the back-end encoder use does an awful lot video transcoding, unequivocally little volume fasten video files.

the transcoding finished controlling on2 flix engine windows works unequivocally well, nonetheless unfortunately isn't means join files (at slightest distant i discern - conjunction assistance nor support unequivocally informative). i'm happy now.

the joining, during moment, finished controlling leadtools multimedia program is, franky, dreadful. it's unparalleled threaded requires sta uses summary siphon isn't accurately fascinating server application. offer designation overwrites the operative codecs bucket the possess eval ones, there proceed prevaricate this.

ideally i'm looking an api reinstate leadtools multimedia one, join 3gp and/or mp4 files. cost isn't too many problem. does anybody have any recommendations?

i know ideal fortitude the possess apparatus here, nonetheless we're intending wmf haven't definitely transitioned win2008 nonetheless need surrogate fortitude integrate months.

update:

i should indicate out encoding means area expertise, i've never many traffic unmanaged formula being comparatively new attention (7 years). i also don't have unequivocally many since office dev lead services-tier/encoder organisation consists only me person, simply don't have lot spend encoder.

something flix engine where lot underlying complexity already burnished some-more i'm looking low-level apis have called differently depending input/output record forms etc.

if have any recommendations, unequivocally useful indicate me during docs used etc.