mpeg4 header

[shizny]

Hello.

I have a few questions.
1. How can I view the header object of an mpeg4 video?
2. What is the size of a long and short form mpeg4 header?
3. I have been splitting a long mpeg4 into small chunks of 15 seconds because of bandwidth issues. The sum of all the 15 second chunks always ends up to be more than what the original clip was. I'm assuming that this is because every file now has a header instead of just one file. Is that true? If so, will each of these chunks have the same header if they were exported exactly the same?

Thanks for the help.

Josh

[celtic_druid]

You are splitting raw a m4v stream? An mp4 file containing m4v?

[shizny]

I'm not sure exactly what I'm using. The end result is a 3gp file that wraps a mp4 codec? I think that is right. Do you know how to extract a header or how big a typical mp4 header file is?

[celtic_druid]

3gp is more of a subset of MPEG-4. Can contain h.263 or m4v. Guess maybe also AVC. Audio is generally amr or aac.

Check out mpeg4ip or gpac. Plenty of tools for extracting info from mp4/3gp's, although I don't know about the header. Removing the header though would make the files unplayable.

[shizny]

thanks for the info on the software. If I'm splitting up the 3gp video files, which are being encoded as m4v, is it possible that the header files have common information which I can extract on all the videos but one and then reattach the header later when I play. In other words, could I prepend a header file to raw video if all the header files are similar.

[celtic_druid]

Well you could use a file splitter, split into chunks and later join.

[shizny]

What could I use as a file splitter. I am using a quicktime script to split up my video now, but that is putting headers at the top of every video. Do you know what the header object looks like. How to extract it?

[celtic_druid]

I mean a general purpose, got nothing to do with video file splitter like SplitIt. Then you can just join back with a copy /b command.

[futurex]

shizny, what is it with you and headers? they're necessary, just let them be!

[shizny]

Well, here is my deal with the headers. I am working with really really tight file size requirements. Tight enough that I have to break up these clips to around 28k. So, if these headers are being created for every clip and they are sizeable, even 2-4k, then I would like to take them off and prepend them when I am ready to use the video. I got the idea to take off the headers because I was adding up the file size of my 2 minute movie when it was split into 15 second chunks, and noticed a sizeable difference between the summation of the chunks and the original video. Then I thought, well, all the chunks are exported the same way, so mabey the header files are all the same. Because of that, mabey I can just put the header of the first of the 15 files into memory of my program, and then add it to all the chunks after they have been downloaded. That could save me enough kb to make my project work.

[shizny]

so nobody knows how to identify and extract header objects?

[bond_d9]

its possible with the mpeg4vol tool from mpeg4ip

[vijaypatidar]

Actually i am working on playing video while it is Downloading and video format is 3gp i am able to play first part of stream (200 kb) but not able to play next part of stream may be that it losses headers information.

how can we append header information in second Part of stream pls help me.

have any one solve above "shizny's" matter?
Thanks

vijay patidar

[vijaypatidar]

Hai is there any person who can answer above qusetion?

vijay patidar