MP4 ISOM Demuxer for unevenly distributed tracks

[varsill]

The Membrane.MP4.ISOM.Demuxer suffers from the problems when samples from different tracks are packed unevenly in the .mp4 file.
For instance it happens when after reading 3MB of the .mdat box, the user can resolve video samples corresponding to 30s of video, but only to 1s of audio.
If the user would like to have the audio and video tracks synchronized, it becomes necessary to buffer the samples from the video track, which might lead to extensive usage of memory.
Possible solutions:

• bind the Demuxer more tightly to reading file from the system so that it can freely seek in the file
• use the SeekEvent API to seek in the File.Source
• allow user to specify the desired type track that the demuxer should resolve - with that approach, the user could easily spawn two demuxers, one for video and one for audio track