MP4 container file formats and methods of processing MP4 container files

摘要

A file that is compatible with a media player application that reads media files compliant with MP4, is created by including in the file a parent container containing child containers. The child containers include a metadata container containing metadata relating to the media presentation and a media data container containing media samples for multiple tracks of the media presentation. The metadata container contains multiple child containers containing metadata for the multiple tracks respectively. The metadata container contains at least one additional child container that reserves free space in the metadata container but does not contain metadata, whereby in the event of adding a track to the presentation the free space in the additional child container may be overwritten with metadata for the added track without affecting the size of the metadata container.

主权项

1. A method of processing a file containing a presentation that is compatible with a media player application that reads media files compliant with MP4, wherein the presentation includes a first track comprising video data, the first track composed of fragments corresponding to respective intervals, said method comprising:
adding to the file a second track comprising video data, the second track including pre-buffered data, wherein the pre-buffered data is composed of fragments corresponding to said intervals, whereby for each fragment of the pre-buffered data of the second track there is a corresponding fragment of the first track, and each track represents a timed sequence of frames, selecting, at a time of interest, a fragment of the second track included in the pre-buffered data for insertion sequentially in time next to one of the fragments of the first track, scanning the selected fragment of the second track and selecting an I frame within the selected fragment based on an earliest I frame of the second track subsequent to said time of interest, scanning the fragment of the first track corresponding to the selected fragment of the second track and selecting an I frame within the corresponding fragment, and constructing a media file compliant with MP4, wherein the media file contains a presentation including the first track and the second track utilizing data commencing with the selected I frame of the second track.