h.264 with gaps in frame num

[sitarmac]

I have a H.264 elementary bit stream with gaps in frame numbers ( it has some dropped packets ). VLC (0.9.2) is unable to play the stream properly.
But when I convert the H.264 file to mp4 format ( using YAMB), I am able to play it perfectly. Whats going on ? Does the mp4 file invoke a different
decoder than the one used for an elementary stream ?