dynamic mpeg4 header: creating file that pulls data out of two other files

[thommyfilm]

we're looking for a system that can do the following:
a user clicks on a download link: he gets a standard compliant mpeg4 movie (ca. 1 gb) with a personalized title during the first 3 seconds.

or in detail:
1. a user clicks on a movie download link on a website (mpeg4, php/mysql)
2. some information is pulled out of a database
3. a short movie (3 secs) containing this info as a title is generated (we currently do this with quartz under os x)
4. now this short movie will is joined with a very long movie (90 min 1 gb) that is already encoded with the same parameters
5. the download of the new movie (short and long conntected to one mpeg4 movie file) begins

and now it comes: this has to happen very fast (ca. 5 secs). we only found solutions where the new moviehas to be written down to a new file, before the download starts. even with a fast machine this is very time consuming. it also needs a lot of storage.

is there a possebility to do this directly?
we imagine something like modifying an existing mpeg encoder to accept two files as an input then ultimately generating the mpeg4 header and passing it on to the webserver to start with the download. can the movie information be pulled out of the two existing files? for the user it has to be like just downloading one file.

currently we have a os x leopard server. we would also be ready to switch to linux.
any help is apreciated. would be really great...

[thommyfilm]

an other idea: suppose the long movie is already prepared: is there a tool that can change some frames or GOPs inside an existing mpeg4/h264 file? the size and duration and everything would stay the same. just the data of a few gops is replaced. i guess like this the header would not have to be rewritten?

any thoughts?

[guns1inger]

What you really need is a real time GOP level editor that can be added to the stream as it leaves the server. AVI Demux is open source, has scripting capabilities, and comes in several versions for OS X, Linux and Windows. It can certainly do what you need from the GUI. It may be able to do what you need from a script as well. Contacting the authors would be a good first step : http://www.avidemux.org/admWiki/index.php?title=Main_Page