You could use free tools:
1) Mux your AVCHD files to TS container using tSMuxer. You can cut your resulting TS without preview in tSMuxer - lossless
http://www.videohelp.com/tools/tsMuxeR
2) Cut your "short" TS using preview in TSSniper - lossless
http://www.videohelp.com/tools/TSSniper
3) Demux your short TS files using tSMuxer again to elementary streams - H.264 video and audio streams - lossless
4) Open elementary H.264 streams in avc2avi and mux them to AVI container (there will are AVI files with H.264 with no audio, don't forget set H.264 - H CAPITAL LETTER!!!, plus manual framerate changing to standard - 23.976 or 25.0 or 29.97 etc - the same as on step 1) - will be shown in tSMuxer) - lossless
http://forum.doom9.org/showthread.php?t=110083
5) Add elementary audio streams to your silent AVI files using VirtualDubMod - from AutoGK package - lossless
http://www.autogk.me.uk/modules.php?name=Downloads
6) Convert your AVI (H.264) to AVI (XVID) using AutoGK - if your AVCHD files were interlaced AutoGK will remove it with AVISynth filters - with loss, final encoding
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