modifying mpeg4 without writing to disk

[thommyfilm]

hello

we want to achieve a very tricky thing. no one was able to offer a real solution for this up to now. so it's a real challenge!

we're looking for a system that can do the following:

1. a user clicks on a movie download link for on a website (mpeg 4, 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. this short movie is connected 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 movie) begins

and now it comes: this has to happen very fast (ca. 5 secs). we only found solutions where the two movies have 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 mp4box 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.


cu t.

[Cornucopia]

SMIL scripting? (Like ASX/WVX scripting for ASF/WMV which is certainly doable for something like what you're talking about). Oh, that would probably be for QT. For MP4, it would be some XML-type script.

Scott

[Relayerman]

Or take another approach. Make the long movie the WHOLE movie, but use the link the user clicks on just an index to both the short and long. They see the short, but download the already-built long version as its indexed to the same link. (I probably don't quite understand what you're trying to acomplish). What is the purpose of joining the short with the long to begin with? Just write a script that when the user clicks on the link you read the DB, points to the WHOLE movie, but script makes the view stop after the alotted 3 sec. If they download they get the pre-built whole movie. Forget the joining thing as a real-time process. Pre-join your parts.

[Cornucopia]

Relayerman, that's what I was just mentioning about SMIL & ASX. That's how those work--it's like a TV station playlist played out directly from their server: Episode pt1 + CommercialBreak+Episode pt2, etc. End-users clicking on the link is like switching to that channel at the top of the hour; No way is the TV station PRE-COMBINING the show+commercials.

Scott


>>>>>>>>
Edit (added): do a google search on "Metafile" "Playlist" SMIL QTL ASX. That'll get you lots of good info. And BTW, you can put MP4s as source files in a SMIL, QTL or ASX playlist, it works; you just have to choose which player you are intending people to use.

[thommyfilm]

hello all


thanks for the input. playlists don't help. we are looking for a solution where the user downloads just one standard compliant mpeg4 file. this movie should play on as many players as possible. he gets blabla.mp4 and there is a personalized title at the beginning.

may be i was too specific? i'm just looking for an easy solution to do the following:

a user clicks on a link on a website. he gets a link to a mpeg4 movie file that is personalized: there is a special title at the beginning of the movie (ca. 3 secs).

would be cool if the user would not have to wait to long for the download link to appear (ca. 10 secs). the movie is around 90 minutes long. so it is around 1 gb size. i'm looking for a solution that can do this without creating to much harddisk activity on the server. if 1 gb have to bee copied it takes very long for the user to wait and the hds a used a lot. would be cool if a server could process several request in parallel.

cu t.

[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?