encoded file has more frames than source file(AVI)

[thuongshoo]

HI ! I have a AVI file, DIVX5 , 4664 frames . I converted it into mp4/x264. VD says that mp4 has 5591 frames. I did this jobs for the third times but mp4 file still has 5591 frames. I did do SSIM but Avisynth always says " ...same lenght..." . Certaintly, I also trim the first frame but problem still remain.
I don't know why. Can you explain to me ?
thanks !

[setarip_old]

Just a stab in the dark but, the difference seems fairly close to that which would result from a conversion of 23.976fps to 29.970fps...

[thuongshoo]

I used Avisource function . Oh ! maybe my file is damage ? so AVIsoucre set wrong fps ?
thanks !

[thuongshoo]

Thanks ! directshowshource(..,fps=25) give 4664 framse !Thank setarip_old !