There is the MP4 container format, and then there is the AAC audio stream, one of several things you'll find in the container.Look here: http://www.hydrogenaudio.org/forums/index....showtopic=68576Is there a reason you need to make your own cutter? MP4Box, ffmpeg, and various GUI front-ends for them already do a good job.mp3DirectCut recently added AAC support as well, although I think it only works on the raw .aac files, not MP4/.m4a files (someone correct me if I'm wrong).
"MP4" is too generic. Maybe you are thinking of such that only contain one audio (probably AAC) track ?At first you have to understand MP4 format by reading spec. You have to work mainly with some mp4 "box" structure such as stts, stsc, stsz, and stco as well as actual media samples (data) which goes under mdat box. All of these are considered as index to actual media samples, therefore required to edit.AAC has inter frame dependency by overlapped nature of MDCT (and bit-reservoir). Therefore, it needs some pre-rolling to start playback at some arbitrary point.When you implement cutting, you have to take this into account.You will also need some way to express priming/padding samples for gapless playback.
You want us to do your homework for you?