Quicktime File Format (2012-08-14).pdf

Some Useful Examples and ScenariosInterleaving Movie DataBecause the track is now back to its original duration of 10 seconds, its duration in the track header atom is6000, and the movie’s duration in the movie header atom is 6000.Interleaving Movie DataIn order to get optimal movie playback, you must create the movie with interleaved data. Because the datafor the movie is placed on disk in time order, the data for a particular time in the movie is close together inthe file. This means that you must intersperse the data from different tracks. To illustrate this, consider a moviewith a single video and a single sound track.Figure 6-7 (page 358) shows how the movie data was collected, and how the data would need to be playedback for proper synchronization. In this example, the video data is recorded at 10 frames per second and theaudio data is grouped into half-second chunks.Figure 6-7TimeNon-interleaved movie data1 sec2 sec 3 secVideo track1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32Audio track1 2 3 4 5 6 7After the data has been interleaved on the disk, the movie data atom would contain movie data in the ordershown in Figure 6-8 (page 358).Figure 6-8Interleaved movie dataFile'moov''mdat'1 2 3 4 5 6 7 8 9 10 11 12 13 14151 23 42012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.358