HDMI 2.0 vs DisplayPort 1.4 Bandwidth Explained

Description 

This document provides a technical comparison and practical guide for bandwidth assessment of common video formats using HDMI 2.0 and DisplayPort 1.4.

High-definition video and audio interfaces like HDMI and DisplayPort are essential for delivering content between devices such as PCs, monitors, and TVs. Among the popular standards, HDMI 2.0 and DisplayPort 1.4 are often compared due to their widespread use and performance capabilities. 

Note - Since HELIOS does not support DSC, the table above are references to uncompressed limits. 

Overview of HDMI 2.0

There are a variety of other important details and limits to be aware of.  Below is a detailed overview of HDMI 2.0. 

• Total Bandwidth: 18.0 Gbps
• Maximum Data Rate / Effective Bandwidth (after encoding overhead): ~14.4 Gbps 
• Encoding Scheme:TMDS (Transition Minimized Differential Signaling) with 8b/10b encoding
• Maximum Resolution & Refresh Rate:
  • 4K (3840x2160) at 60 Hz with 8-bit color
  • 4K at 60 Hz with 4:4:4 chroma requires compression for HDR
  • 1080p at 240 Hz is also supported (with lower bit depth / etc.)

Overview of DisplayPort 1.4 

Similar to HDMI, there are a variety of other important details and limits to be aware of.  Below is a more detailed overview of DisplayPort 1.4.

• Total Bandwidth: 32.4 Gbps (across 4 lanes at 8.1 Gbps each)
• Maximum Data Rate / Effective Bandwidth (after encoding): ~25.92 Gbps (with 128b/132b encoding)
• Encoding Scheme: 128b/132b encoding (only ~3% overhead)
• Maximum Resolution & Refresh Rate:
  • 8K (7680x4320) at 60 Hz with DSC (Display Stream Compression)
  • 4K at 120 Hz with HDR (with or without compression)
  • 1080p at 240 Hz (or higher) 

Calculating Video Bandwidth Requirements

To determine whether a video resolution and refresh rate will fit within the bandwidth limits of HDMI 2.0 or DisplayPort 1.4, you need to do some calculations.  Luckily, calculating bandwidth is a very simple process.  Below is the basic formula:

Bandwidth (Gbps) = Resolution × Refresh Rate × Bits per Pixel × Overhead Factor  / 1,000,000,000

Formula Variables:

• Resolution = width × height

• Refresh Rate = in Hz

• Bits per Pixel (bpp) = color depth × 3 color channels

• Overhead Factor = accounts for transmission encoding and blanking intervals

Typical Overhead Factors

Depending on the blanking algorithm used, the overhead can vary greatly. In most cases, it is best to use the Reduced Blanking (rbv2 for example) to maximize bandwidth availability.  

Overhead ranges:

• HDMI 2.0 (8b/10b encoding + blanking): ~1.2 – 1.4

• DisplayPort 1.4 (128b/132b encoding + blanking): ~1.05 – 1.15 (more efficient)
  

Example Calculations 

Example 1: 4K @ 60Hz, 8-bit RGB on HDMI 2.0

• Resolution: 3840 × 2160 = 8,294,400 pixels

• Refresh Rate: 60 Hz

• Color Depth: 8-bit RGB = 8 × 3 = 24 bpp
  
  

Raw bandwidth:

8,294,400 × 60 × 24 = 11.95 Gbps

Including overhead (× 1.2):

11.95 × 1.2 ≈ 14.34 Gbps

Example 2: 4K @ 120Hz, 10-bit RGB on DisplayPort 1.4

• Resolution: 3840 × 2160 = 8,294,400 pixels

• Refresh Rate: 120 Hz

• Color Depth: 10 × 3 = 30 bpp
  
  

Raw bandwidth:

8,294,400 × 120 × 30 = 29.86 Gbps

Including overhead (× 1.1):

29.86 × 1.1 ≈ 32.85 Gbps 

This slightly exceeds DisplayPort 1.4’s raw bandwidth (32.4 Gbps), so will not be supported on HELIOS.