CBR vs VBR: Choosing the Right Bitrate for Your Video

In the world of video streaming, there are two main types of bitrate technology: Constant Bitrate (CBR) and Variable Bitrate (VBR). While both methods deliver high-quality video content, they differ in their approach to compressing and transmitting data. Understanding the difference between CBR and VBR is crucial for choosing the right streaming solution for your needs.

In this article, we'll look at the pros and cons of each technology and discuss scenarios where one might be better suited than the other.

Table of contents

1. What is bitrate?
2. What is constant bitrate (CBR)?
3. What is variable bitrate (VBR)?
4. What is constant quality (CQ)?
5. CBR vs VBR: side-by-side comparison
6. When to use CBR vs VBR?
7. CBR or VBR for video streaming
8. Recommended encoder settings
9. CBR vs VBR in WebRTC video conferencing
10. Frequently asked questions

What is bitrate?

Bitrate refers to the amount of data transmitted per second in video streaming and encoding. It's like the flow of water through a pipe – the higher the bitrate, the more data flows, affecting both video quality and file size.

Bitrate is measured in units such as kilobits per second (kbps) or megabits per second (Mbps). Higher bitrates generally mean better video quality but also result in larger file sizes, which affects storage and bandwidth usage.

Adjusting the bitrate achieves different quality levels in video streaming. Resolutions like 240p, 360p, 480p, 720p, and 1080p indicate different levels of video quality. Higher resolutions and frame rates require higher bitrates to ensure clear visuals and smooth motion.

What factors influence bitrate?

Several factors influence bitrate requirements:

1. Resolution plays a significant role, as higher resolutions require more data to display detailed images.
2. Frame rate is another consideration – a higher frame rate needs a higher bitrate for smooth playback.
3. Codecs also affect bitrate. Efficient codecs can achieve better compression, reducing bitrate without compromising quality.

What is CBR?

Constant bitrate, or CBR, refers to transmitting data at a constant rate. In the context of video encoding, CBR means an encoder outputs data at a fixed bitrate, so it is not responsive to the size or complexity of the content it is processing.

Because CBR uses a constant transmission rate, the bitrate is set and measured as a single value. In most cases, video conferencing platforms set this bitrate relatively high so that the encoder can handle more complex content when it occurs.

To achieve good video quality and avoid buffering, streaming services often use CBR rate control to regulate the amount of data transmitted per second, providing a consistent viewing experience. CBR is a popular choice for many streaming situations because it has been a standard in online streaming for a long time, and it is compatible with most devices.

What is VBR?

Variable bitrate encoding, or VBR, refers to data being transmitted at a variable rate. With video encoding, the encoder packages data according to its complexity, so the transmission is optimised to process higher bitrates and transmit larger files where needed.

In encoding terms, data is output at a set rate per time segment, and the variable bitrate is measured by averaging the bitrate of the complex segments across the entire file.

The fluctuating nature of VBR makes it well-suited to on-demand video, where it can take longer to process data. It is important to remember that VBR works best with on-demand video and less well with live streams.

What is constant quality (CQ)?

Constant Quality (CQ) is an alternative encoding mode that aims for a fixed visual quality while keeping the highest compression in a single encode. Each frame is allocated enough bits to achieve the required visual quality.

To get the best balance between video quality and file size, many video converters and video editors adopt Constant Quality as the x264 and x265 encoding modes (where it is often called CRF, constant rate factor).

Unlike CBR and VBR – where the bitrate is either fixed or varies based on content complexity – CQ aims to maintain a consistent level of quality across different bitrates. Regardless of scene complexity, CQ targets a consistent viewing experience.

In CQ mode, the encoder allocates the bitrate needed to maintain the specified quality level: higher bitrates for complex scenes to maintain clarity, and lower bitrates for simpler scenes, reducing file size while retaining acceptable quality.

CBR vs VBR: side-by-side comparison

When it comes to video streaming and encoding, the choice between Constant Bitrate (CBR) and Variable Bitrate (VBR) can significantly affect the quality of your streaming experience.

Both CBR and VBR are widely used, each with its own features and benefits. To help you decide, here is a side-by-side comparison.

When to use CBR vs VBR?

Bandwidth constraints and network conditions

Where bandwidth is limited or network conditions are unstable, Constant Bitrate (CBR) is usually the better choice:

• CBR provides a stable streaming experience, helping prevent buffering and interruptions even in challenging network environments. If your audience includes viewers with varying internet speeds, CBR can deliver consistent quality for everyone.
• VBR works best on stable, high-speed networks. With its adaptability, VBR optimises data usage and provides better video quality when the network permits, so viewers with fast connections can enjoy higher resolution and clearer visuals.

Video content types

The choice should also consider the complexity of your content:

• CBR suits simpler content with consistent scenes, such as podcasts or audio-only streams, where a fixed bitrate maintains stable quality.
• For dynamic content with varying complexity, such as on-demand videos, films, or TV shows, VBR is the recommended option. Its ability to allocate higher bitrates to complex scenes improves the visual experience.

CBR or VBR for video streaming

Choosing between CBR and VBR for video streaming depends on factors such as content complexity, audience network conditions, and desired video quality.

As mentioned earlier, CBR provides consistent quality but can lead to buffering or stuttering if the viewer's connection fluctuates. VBR adjusts quality based on content complexity, providing smoother playback but potentially sacrificing some consistency.

As a rule of thumb: CBR is the stronger option for live video streaming, whereas VBR is the stronger option for on-demand video.

Recommended encoder settings

Several encoders and codecs are common in video streaming, including x264 (H.264), x265 (H.265), and newer options like H.266/VVC. Each has its own strengths and weaknesses, so it is worth choosing the right one for your specific use case.

General guidelines for setting up CBR and VBR encoding

When setting up CBR and VBR encodes, a few general guidelines help:

1. Bitrate targets: choose a bitrate target based on the desired video quality and audience expectations.
2. Frame rates: select a frame rate that aligns with the source material and intended display format.
3. Resolutions: choose a resolution that balances video quality and file size.

Tips for optimising encoder settings by use case

1. Low-latency live streams: use low-latency settings and optimised presets to minimise delay and ensure real-time delivery.
2. High-quality on-demand content: use higher bitrates and advanced presets to deliver excellent video quality.

Modern codecs and per-title encoding

Encoder choice matters as much as the bitrate mode. Established encoders like x264 (H.264) and x265 (H.265) remain the most compatible, while newer codecs such as H.266/VVC offer up to 40–50 per cent better compression than H.265. In 2026, however, most workflows still serve a fallback ladder of H.265 and H.264 for devices that cannot decode VVC yet, so multi-codec adaptive delivery is the norm.

A useful middle ground is capped CRF (constant rate factor with a bitrate ceiling). It behaves like constant quality on easy scenes – saving bandwidth – while capping the peak bitrate so delivery stays predictable, effectively giving per-title efficiency with CBR-like safety. For live and low-latency work, Apple's HLS guidance of constrained VBR, with peaks kept under about 125 per cent of the target, is a practical compromise.

CBR vs VBR in WebRTC video conferencing

Real-time video conferencing has its own constraints, and they push the choice toward a CBR-style approach. Because every extra moment of delay is noticeable in a live call, platforms built on WebRTC avoid the large bitrate spikes that classic VBR can produce, since those bursts work against low latency.

Instead of a simple CBR-or-VBR switch, WebRTC continuously estimates the bandwidth available on each connection and adjusts the encoder's target bitrate to match. This is handled by congestion-control algorithms such as Google Congestion Control and transport-wide congestion control (TWCC), which combine delay and loss signals to decide how much each stream can send. The encoder then holds close to that moving target – a constrained, CBR-like behaviour around a bitrate that itself changes with network conditions.

The result is adaptive bitrate: more data is allocated to active speakers and shared screens, less to idle thumbnails, and the whole call scales down gracefully when one participant's connection weakens, rather than forcing everyone to a low-quality floor. This often works alongside simulcast, and typical per-stream targets range from around 100 kbps for small thumbnails up to 2–4 Mbps for an HD active-speaker stream. How much headroom is available depends on factors covered in our guide to latency and bandwidth.

Bandwidth estimation in WebRTC is still evolving: newer feedback formats – RFC 8888 congestion control feedback, and ECN/L4S signalling – are beginning to ship in some implementations in 2026, though they are not yet the default everywhere.

Frequently asked questions

Which gives better quality, CBR or VBR?

For the same average file size, VBR usually delivers better visual quality because it spends bits where they matter most – complex motion, fast cuts, and detailed scenes. CBR keeps quality steady but can show compression artefacts in busy scenes when the fixed bitrate runs out of headroom.

Should I use CBR or VBR for live streaming?

CBR is the safer choice for live streaming on Twitch, YouTube Live, or webinar platforms because it produces a predictable, steady data rate that streaming servers and CDNs handle well. VBR can confuse rate-limited streaming pipelines and cause buffering for some viewers.

Is VBR better for storage and file size?

Yes – for the same perceived quality, VBR files are typically 20–40 per cent smaller than CBR because the encoder spends fewer bits on simple scenes. This makes VBR the standard choice for video on demand (VOD), archival, and any pre-recorded content where smaller files matter.

What's the difference between CBR, VBR, and CQ (Constant Quality)?

CBR fixes the bitrate. VBR fixes a target average bitrate but varies up and down. CQ (also called CRF in x264 and x265) fixes a quality target instead – the encoder spends whatever bitrate is needed to hit a constant quality score, so file size is unpredictable. CQ is popular in video editing because it gives the most consistent visual result.

Which bitrate is better for CCTV recording?

VBR is the standard for CCTV because most surveillance footage is mostly static (empty rooms, car parks) with occasional motion. VBR keeps file sizes manageable during quiet hours and ramps up only when something happens. CBR is used in CCTV only when the recording system requires a strict, predictable data rate.

What bitrate does video conferencing use?

Video conferencing platforms typically use adaptive variable bitrate over WebRTC, with per-stream targets ranging from about 100 kbps for small thumbnails up to 2–4 Mbps for HD active-speaker streams. The encoder reacts to real-time network conditions, raising or lowering bitrate per participant rather than per call.