MPEG Encoding Methods
There are three common methods of encoding video: CBR (constant bit rate, also known
as one-pass), one-pass VBR (variable bit rate), and two-pass VBR.
• CBR (one-pass) method: You choose a bit rate and it is used for the entire video,
regardless of its content. The advantage of this method is that you can reliably predict
the final encoded file size. By adjusting the bit rate, you can ensure the video will fit
on the DVD. The disadvantage is that the same bit rate gets applied to all of the video,
regardless of the motion content. You must choose a high enough bit rate to provide
acceptable results for the scenes with motion, even if they are only a small part of the
Preparing Video Assets
• One-pass VBR method: You choose a basic bit rate and a maximum bit rate. The encoder
detects the amount of motion present in the video as it encodes and adjusts the bit
rate appropriately—scenes with motion use higher bit rates (up to the maximum setting
you choose) and scenes with little motion use the lower, basic bit rate. The disadvantage
of this method is that the quality will not be as good as with the two-pass VBR method.
• Two-pass VBR method: You choose a basic bit rate and a maximum bit rate, just as with
the one-pass VBR method. The difference is that the encoder makes two passes through
the video to encode it. The first pass examines the video to learn about its motion
content. The second pass performs the encode, varying the bit rate to provide better
results in scenes with motion (as compared to the one-pass VBR method). The
disadvantage of this method is that it takes twice as long as the one-pass VBR method.
With the VBR methods, the basic bit rate setting determines the encoded file
size. The maximum bit rate setting does not affect the file size. Additionally, the VBR
methods are most effective when the maximum bit rate is about double the basic bit
rate, or at least 1 to 3 Mbps higher than the basic bit rate.
The integrated MPEG encoder allows you to select which of these methods you want to