Recently, Thunderbolt has become a leading protocol in high-speed transmission. Its applications extend beyond personal laptops, encompassing docking stations, monitors, external hard drives, and external display cards. Thunderbolt not only facilitates data transfer but also serves as a conduit for audio and video between display devices, delivering crisp high-resolution graphics. However, when manufacturers market their Thunderbolt products with high-resolution audio/video transmission capabilities, issues may arise during connections to different devices, leading to a detrimental user experience.  In this article, Allion will share our experience and provide solutions to address this challenge.

Thunderbolt Audio/Video Transmission Error and Solutions

A laptop equipped with Thunderbolt can connect to a monitor using a Thunderbolt cable. This allows users to enjoy high-resolution videos, play graphics-intensive games, and even use the monitor as a hub to chain other monitors or storage devices.

Leveraging our extensive experience as a professional lab, Allion has encountered various cases where issues arise during the connection process. These include scenarios where there is no response while the monitor is connected to the laptop, immediate and repeated connections and disconnections, and instances where the monitor does not appear in the device manager or Thunderbolt control center. Despite attempting troubleshooting steps such as re-connecting cables and rebooting, the issue persists.

Upon analysis by the Allion consultant team, it was identified that the SBU(Sideband Use) voltage of the notebook was insufficient. SBU is utilized for connecting in the default mode of products. When Thunderbolt products connect, the system determines the construction of the correct link, ensuring functional operation based on the sideband level. However, if one product detects an incorrect sideband on the other, the connection link may fail.

As shown in the image below, when two Thunderbolt devices are connected, they communicate through the sideband. This communication reveals both high and low voltage levels of the sideband signal. If the voltage values are either too high or too low, it can lead to a failed device connection, resulting in a loss of functionality.

Allion leverages extensive experience and professional equipment, featuring specific test fixtures, power supplies, and oscilloscopes. Our services not only guarantee the connection quality of products but also preemptively address the risk of consumer returns arising from post-shipment transmission issues.

Faster, Easier, Better: The Most Trusted System Testing Consulting Service

Allion has decades of experience with computer system certification and compatibility testing. Our team of professional engineers can quickly identify issues and provide solutions for our clients.


Allion can provide clients with fast and accurate evaluations that effectively shorten schedules for certifications. Allion is an official Thunderbolt certification laboratory. We also have a complete range of Thunderbolt testing equipment that can ensure compatibility amongst different kinds of HDMI products, helping you with your quality control along the way.

  • Quickly provide product development certification strategies with rich testing experience and collection of testing equipment
  • Quickly obtain logo certification


Allion has a complete range of Thunderbolt hardware certification testing equipment and testing environments. With our testing solutions, we can ensure each client’s certification process is qualitative, quantitative, and reproducible. We can assist our clients in obtaining accurate test results easily, ensuring the quality and performance of their products.

  • Provides more accurate results
  • Provides professional issue isolation and debugging support for our clients to make product development more convenient


Not only does Allion have professional teams with decades of experience, but we also know how to design quantitative tests and user scenario simulations, allowing our clients to comply with requirements and user expectations. Allion’s professional teams can also provide suggestions for product modifications, assist with supplier management, and help with specifications requirements from international associations during product development. This further enhances the quality of our client’s products, ensuring high standards that comply with international specification requirements.

  • Provides a better and more complete experience for brands to establish ODM ecosystem plans
  • Provides more complete user scenario testing solutions


If you have any requirements, please contact with us.