Terminology » Networking Basics » CBR vs VBR: Constant Bit Rate vs Variable Bit Rate

CBR vs VBR: Constant Bit Rate vs Variable Bit Rate

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This article explores the differences between Constant Bit Rate (CBR) and Variable Bit Rate (VBR) encoding methods, highlighting their strengths and ideal use cases. Let’s dive in!

CBR - Constant Bit Rate

  • Ideal for: Timing-sensitive traffic like voice calls and interactive video conferencing.
  • Key Feature: Maintains a consistent data rate throughout the transmission.
  • Benefit: Ensures a predictable and consistent delay across the network.
  • Example: Commonly used in ATM (Asynchronous Transfer Mode) networks.

VBR - Variable Bit Rate

  • Modes: VBR offers two primary modes: VBR-nrt (non-real-time) and VBR-rt (real-time).
  • Ideal for: Bursty data applications where data flow isn’t constant.
  • Key Feature: Allows for both a pre-assigned average data rate and the ability to vary the rate based on content complexity.
  • Examples of VBR-rt: Compressed video and audio in teleconferencing, as well as general multimedia applications.

CBR vs. VBR: A Detailed Comparison

The following table summarizes the fundamental differences between CBR and VBR:

FeaturesCBR - Constant Bit RateVBR - Variable Bit Rate
Traffic typeSteadyBursty
Timing/Delay variationSensitiveInsensitive to minimal delay variation (VBR-nrt). Sensitive (VBR-rt)
ApplicationsVideo conferencing, video, PBXData and imaging in VBR-nrt (non-realtime). Compressed video, audio, and tele-conferencing in VBR-rt (realtime)