Try iFlicks
I've tried most of the video converting software available for Mac OS X. iFlicks is definitely one of the best since it can remux (video pass through) both H.264 MKVs and MPEG4 AVI (encoded with DivX/Xvid) and handle meta data.
Remuxing takes 1-10 minutes compared to re-encoding which takes anything from 20 min to 3 hours.
I've tried most of the video converting software available for Mac OS X. iFlicks is definitely one of the best since it can remux (video pass through) both H.264 MKVs and MPEG4 AVI (encoded with DivX/Xvid) and handle meta data.
Remuxing takes 1-10 minutes compared to re-encoding which takes anything from 20 min to 3 hours.