DisplayPort: What is High Bit Rate? HBR2 vs HBR3

DisplayPort is a digital interface that enables users to get higher resolutions and faster refresh rates, making it indispensable for high-performance gaming, multimedia animations, image editing, and content creation workflows.

DisplayPort is a video interface that VESA (Video Electronics Standard Association) introduced in 2006 to replace older VGA and DVI interfaces.

Since 2006, VESA has introduced several upgraded versions of the DisplayPort standard, progressively supporting higher performance and essential features, including multi-display support.

Delivering high resolutions and faster refresh rates requires vast amounts of data, so to keep up with the demand, VESA upgraded DisplayPort’s bandwidth from 8.64Gbps with DisplayPort v.1.0 to 80Gbps with DisplayPort 2.1.

DisplayPort’s bandwidth (or bit rate) refers to the maximum amount of data the interface can handle at a given time. Each version of DisplayPort has a well-defined bit rate, which VESA defines as the transmission mode, and it governs the specifications and capabilities of that version of DisplayPort.

What is High Bit Rate?

High Bit Rate (or HBR) is a DisplayPort transmission mode with a bandwidth of 8.64 Gbps. Compared to 1080p resolution on DisplayPort RBR (Reduced Bit Rate), DisplayPort HBR supports up to 4K@30Hz video.

When DisplayPort 1.0 (or RBR) was introduced in 2006, it had a bit rate of 1.62 Gbps on each of its four lanes, allowing it to support only 1080p video. This meant that the total bandwidth of RBR was 6.22 Gbps, but only 5.18 Gbps (about 80% of the bandwidth) was meant for carrying video data; the remaining 20% were encoding overheads.

While HBR retained the high encoding overheads, it introduced a higher bandwidth per lane (2.70 Gbps), increasing the total bandwidth to 10.8 Gbps, of which 8.64 Gbps was for video data. Thus, DisplayPort HBR supports better picture quality with support for either 1440p@60Hz or 4K@30Hz.

HBR was available on the earliest versions of DisplayPort, enabling the use of 4K monitors as early as 2007. With successive version upgrades and growing demand for higher resolutions, VESA labeled various transmission modes as HBR and suffixed them with a number to prevent confusion.

HBR2: Double The Bandwidth – Double The Monitors

In 2009, VESA introduced HBR2 to keep up with the ever-expanding demand for higher resolutions, refresh rates, and better color definition. This transmission mode was available on DisplayPort v.1.2 and supports video up to 4K@60Hz.

DisplayPort 1.2 increased the bandwidth from 10.8 Gbps to a total bandwidth of 21.6 Gbps. The more-than-double bandwidth meant there was room for a lot more data to be transmitted between peripherals. This resulted in the introduction of DisplayPort’s most significant feature, Multi-Stream Transport (MST).

MST allows you to connect multiple monitors using a shared bandwidth. DisplayPort 1.2 and MST gave users tremendous flexibility by offering various monitor configurations with as many as four WUXGA (1920x1200p) screens running at an impressive 60Hz refresh rate. This meant you could use multi-monitor setups to multitask efficiently, and it has considerable applications in productivity and creative workflows.

Alternatively, it allowed you to choose a high-resolution 4K@60Hz configuration, ideal for high-end gaming, content creation, or watching ultra-high-definition videos. The number of monitors and the supported video are inversely co-related, meaning you must sacrifice resolution (and refresh rate) if you want to run more than one display unit. The reverse is also true.

HBR3: Double The Resolution

While HBR2 was ideal for 4K displays, the need for 5K (and higher) displays justified VESA’s upgraded HBR3 standard. DisplayPort v.1.3 and DisplayPort v.1.4 use HBR3 and support significantly higher resolution displays of up to 8K@60Hz (in a single-monitor setup) using DSC.

Digital Stream Compression (DSC) is a lossless video compression technology VESA uses to minimize data transmission and optimize the DisplayPort link’s channel bandwidth. VESA introduces this technology with DisplayPort 1.4, encoding (and decoding) video signals in real-time. Moreover, these compressed video signals have low latency, making them ideal for real-time applications like video conferencing and gaming.

Like HBR2, HBR3 also has high overheads (20%) attributed to video encoding, an issue VESA resolved in later versions of DisplayPort. Despite that, HBR3 increased the total bandwidth to 32.4 Gbps, giving each of the four data lanes a bandwidth of 8.1 Gbps and making DisplayPort 1.4 the most popular DisplayPort version due to its support for high-resolution monitors.

In a dual-monitor configuration, HBR3 supports two 4K displays with a 120Hz refresh rate, ideal for highly immersive gaming. It also supports a triple and four-monitor setup with modest resolutions and refresh rates, making HBR3 a versatile transmission mode suitable across several use cases.

HBR2 Vs. HBR3 Comparison

It must be mentioned that while HBR2 and HBR3 are DisplayPort specifications, DisplayPort uses its version numbers for marketing. So, while it’s rare to find terms like DisplayPort HBR2 or DisplayPort HBR3, most manufacturers use words like “DisplayPort v.1.3”, “DisplayPort v.1.4”, and so forth to signify the port’s capabilities. More importantly, this even extends to DisplayPort-rated cables, and you must be mindful of this when purchasing one, as it’s easy to overlook this specification.

Conclusion

HBR2 and HBR3 brought significant improvement when they were launched in 2009 and 2014, respectively. From higher refresh rates to higher resolutions and support for multiple monitors, VESA has stayed ahead of the demand and expectations of the end user.

However, it’s 2023, and both these DisplayPort standards are reaching their capacity (if they haven’t already). The latest DisplayPort versions use Ultra-High Bit Rates (or UHBR) ranging from 40 Gbps (UHBR 10) to 80 Gbps (UHBR 20) and support dual-5K display or uncompressed 8K video at 60Hz.

So, while mainstream computers play catch-up, it may be fruitful to consider the latest technologies to future-proof your workstation.

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