Variable Bit Rate
Variable Bit Rate (VBR) is a method of video encoding where the number of bits used to store or transmit video frames can vary. Unlike Constant Bit Rate (CBR), where each second of video is encoded at the same bit rate, VBR adjusts the allocation of bits depending on the complexity of the content being encoded. For scenes with a high level of detail or fast motion, VBR will allocate more bits, ensuring that the quality remains high. Conversely, for simpler, static scenes, it will use fewer bits, reducing the file size without significantly affecting the perceived quality.
This adaptive bit rate approach allows VBR to more efficiently use storage and bandwidth. By only using the necessary bits to maintain a defined level of quality, VBR can often result in smaller file sizes compared to CBR at a similar quality level. This efficiency makes VBR a preferred choice for pre-recorded content where file size might be a concern, such as streaming video-on-demand services, downloadable videos, and DVD encoding. The flexibility of VBR is also advantageous for media that will be consumed on devices with varying display capabilities and network connections, as it can provide a better balance between quality and resource use.
However, the variable nature of VBR can introduce some challenges. It may cause issues with buffering and bandwidth allocation in live streaming scenarios where network conditions are unpredictable. Also, the encoding process with VBR can be more complex and time-consuming because it involves analyzing the video content more thoroughly to optimize bit rate allocation. Despite these potential downsides, VBR is widely used due to its ability to optimize quality and file size, making it a smart choice for many applications in the digital video industry.
Links
- Wikipedia: https://en.wikipedia.org/wiki/Variable_bitrate
- DaCast: https://www.dacast.com/blog/cbr-vs-vbr/
- Lifewire: https://www.lifewire.com/difference-between-cbr-and-vbr-encoding-2438423