econmic and highest efficient converters are here
AVI Converter converts any formats like MP4, FLV to AVI, H.264 AVI (.avi), DivX(.avi), XviD(.avi) video, or extract audio from AVI and other video formats to AAC, AC3, MP3, M4A, MP2, WAV audio with super speed and excellent quality.
MP4 Converter converts all the mainstream video, like AVI, FLV, WMV to MP4, H.264/MPEG-4 AVC(.mp4), MOV, AVI, and convert audio or take out audio from videos to AAC, AC3, AIFF, AMR, AU, FLAC, MP3, M4A, MP2, OGG, WAV, WMA which is playable on all the MP4 MP3 players, such as iPod, iPhone, PSP, Creative Zen, iRiver PMP, Archos, PS3, Xbox.