CBR or VBR?
CBR (constant bit-rate) and VBR (variable bit-rate) are two ways of encoding video.
CBR encoding uses the same bit-rate for every second of video regardless of the video’s complexity, so quality worsens as the video becomes more complex, and bits are wasted when there is not much action.
In a VBR encode, the encoder uses higher bit-rates for complex sections and lower rates for “easy” sections, constantly adjusting to keep the overall bit-rate to a target value. VBR encoding can provide the same quality as a CBR encode but at a lower overall bit-rate (so you can fit more video on the disc), or better quality than a CBR encode at the same overall bit-rate.
VBR encoding is best for long video durations (100 minutes or more on a 4.7-GB disc). For shorter durations the difference in quality between CBR and VBR is usually not detectable.