Adobe 22030000 User Guide - Page 34

ENCORE CS3 30 User Guide Note: Keep your calculations simple by working with megabits (Mbits) and not megabytes (MB) when bit budgeting. Mbps denotes megabits per second. Also, hard-disk capacity is typically calculated as a power of 2 (1 KB = 2^10 bytes = 1024 bytes) while optical disc (DVD) capacity is labeled as a power of 10 (1 KB = 10^3 bytes = 1,000 bytes). Use the power-of-10 scheme for bit budgeting. The following conversion factors will aid in the calculations: 1 GB = 10^9 bytes = 1,000,000,000 bytes = 8,000,000,000 bits; 1,000,000 bits = 1 Mbit. Average asset size Use the following averages for bit budgeting: Audio If compressed using the Dolby® Digital Stereo standard, audio is generally 192,000 bits per second (0.192 Mbps). Use 0.192 Mbps or reference the settings for the audio encoder you plan to use. Subpictures Insignificant in terms of bit budgeting, unless you include subtitles. If you do include subtitles, use 0.010 Mbps per subpicture stream for calculations. Motion menus Typically have a data rate of 8 Mbps for the transcoded standard-definition video or 40 Mbps for high definition; add this to the audio data rate. (If the video is already DVD- or Blu-ray-compliant, then it won't be transcoded, and you should use the data rate of the video file.) Still menus Typically insignificant in terms of bit budgeting and can usually be left out of the calculation. Still menus average 230 KB in size. Slide shows The asset size for a slide show depends on whether you include transitions or the Random Pan Zoom effect: • If the slide show contains no transitions or effects, the slides are written to the disc as MPEG stills, which require minimal space. Stills average 230 KB in size, which is typically negligible for bit budgeting. If you have a large number of images, however, you should include them in your calculation. • If the slide show includes transitions, then Encore writes both stills and transcoded MPEG video files for the transitions. For example, if a given image appears for 10 seconds, with a 2-second transition at the beginning and the end, then the still is written to the disc (displayed for 6 seconds) as well as two 2-second MPEG video files that contain the transition frames. • If the slide show includes pan and zoom, then Encore transcodes the stills into an MPEG video file. Slide shows with pan and zoom, in essence, become video content and require the same space allotment as video files. For example, a 5-minute slide show that uses pan and zoom throughout counts as 5 minutes of video content for bitbudgeting purposes. Sample budget #1 Bit budgeting for a simple DVD project containing 2 hours and 13 minutes of standard-definition video, without any audio, to be distributed on a 4.7-GB disc proceeds as follows: 1 Calculate the total available disc space in bits. A 4.7 GB disc contains 4,700,000,000 bytes; each byte contains 8 bits. 4,700,000,000 x 8 = 37,600,000,000 bits. 2 Calculate the disc space available for video. Combine the size of the audio, subtitles, motion menus, and 4% of the disc capacity (for overhead, just to be safe) and then subtract that sum from the total available space you calculated in step 1. Since this example has no audio, subtitles, or motion menus, you subtract only the 4% for overhead (1,504,000,000 bits) to get a value of 36,096,000,000 bits.