Roxio DVDit Pro HD, User Manual

Page: 69 / 222

Choosing bit rates for video and audio
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2. Calculate the target video bit rate by subtracting the audio and subtitle bit rate
requirements from the result of step 1. Enter this value in the Target Bit Rate field in the
Project Settings dialog box:
Avg. bit rate: ____ Mbps – (Audio + Sub): _____ Mbps = _____ Mbps
The bit rate for each subtitle track is 0.04 Mbps. See “Compliant video and audio
requirements” on page 64 for audio bit rates.
In this example, using a single stereo PCM audio track (with a bit rate of 1.6 Mbps) and
no subtitles:
6.0 Mbps – 1.6 Mbps = 4.4 Mbps
3. For VBR encodes only : Calculate the maximum video bit rate by subtracting the audio
and subtitle bit rate requirements from the maximum allowed by the DVD-Video format
(9.8 Mbps). Enter this value in the Max Bit Rate field in the Project Settings dialog box:
9.8 Mbps – (Audio + Sub): _____ Mbps = _____ Mbps
In this example, it would be:
9.8 Mbps – 1.6 Mbps = 8.2 Mbps
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Because spikes in the video bit rate can occur even in CBR encodes, we recommend using
video bit rates below 8.0 Mbps with PCM audio, and below 9.4 Mbps with Dolby Digital
audio. This leaves some headroom so that a spike does not push the total bit rate over
9.8 Mbps.
Calculating the minimum bit rate
The Min Bit Rate in a VBR encode should be about half the Target Bit Rate from step 2 or
2.0 Mbps, whichever is larger.
DVDit_Pro_HD.book Page 69 Monday, September 25, 2006 2:32 PM