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Please provide an overview of the MP4 format and how to cut its audio, [TOS #6: was "mp4 file cutter" in CD Hardware/Software]
manimanik19
post Jan 12 2013, 14:05
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I am working with mp4 file cutter.Could anyone please help me how to get the clear overview of mp4 format and how to cut them.
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mjb2006
post Jan 13 2013, 04:34
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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=68576

Is 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).
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nu774
post Jan 13 2013, 04:50
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"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.

This post has been edited by nu774: Jan 13 2013, 05:00
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manimanik19
post Jan 14 2013, 09:39
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QUOTE (mjb2006 @ Jan 13 2013, 04:34) *
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=68576

Is 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).


yes........i am given a project to make my own mp4 cutter.I need to cut the mp4 video file into small video fragments......not only audio......I am not getting how to start...could u plz........

This post has been edited by manimanik19: Jan 14 2013, 09:48
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manimanik19
post Jan 14 2013, 09:45
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QUOTE (nu774 @ Jan 13 2013, 04:50) *
"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.


I didn't mean to cut only audio.....I need to cut the mp4 video files.....just to break the mp4 video into different fragments......could u please guide me how to start and to get the basic idea of mp4 format and how to cut them.....plZZZ
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mjb2006
post Jan 14 2013, 13:38
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You want us to do your homework for you?
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manimanik19
post Jan 14 2013, 13:44
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QUOTE (mjb2006 @ Jan 14 2013, 13:38) *
You want us to do your homework for you?


Hey..!!!I am just asking how to proceed........if u r interested u can do my homework and plz give it 2 me...tongue.gif
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