Qt vs. Web – Total Cost of Ownership

Room B09 12.10.2017 11:30 - 11:55

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Burkhard Stubert
Burkhard Stubert
EmbeddedUse (DBA)

Let xXx be a manufacturer of embedded devices like home appliances, TVs, STBs and printers. xXx produces hundred thousands or even millions of devices per year. If xXx used Qt instead of Web for the HMI of its devices, it could easily save 2.50 to 8 Euros per unit. At a volume of 1 million units, Qt would save xXx 2.5 to 8 million Euros!

xXx must decide now which HMI framework to use for the next 10+ years. The candidates are Qt and Web. The biggest challenge for xXx is that its devices run on CPUs with a wide performance range.

Even in 2017, premium home appliances with touch screens are equipped with single-core ARM Cortex-A8s. Their mid-range and low-end cousins typically run on micro-controllers. These devices lag years behind smartphones. The reason are razor-thin profit margins. xXx anticipates, however, to use slightly more powerful CPUs (Cortex-A9/A15s) in its premium devices in the future and Cortex-A8s and ARM11s into its mid-range devices. It may even replace some micro-controllers by ARM9s in the low-end devices.

xXx is terrified by LGPLv3, which allows users to install modified software versions on its devices. Qt under LGPLv3 is not an option. What is the total cost of ownership (TCO) for a solution with Qt Commercial and Web? Web aficionados will answer: Web costs nothing, as it uses MIT and BSD licenses. Hold it right there! Does Web scale down well over the given range of devices? Not at all!

Facebook could not achieve a good-enough user experience (UX) with Web on an iPhone 4S, which is powered by a Cortex-A9. Netflix spent dozens of person years to achieve a decent UX on devices with a Cortex-A8 or higher holding on to Web.

Qt is known to scale well. VoIP phones on an ARM9 without GPU have a decent UX. Qt runs fluidly on the Raspberry Pi 1 (ARM11 with GPU). Many harvester terminals, home appliances, in-vehicle infotainment systems and in-flight entertainment systems run on an i.MX51 or i.MX53 (Cortex-A8). The i.MX6 (Cortex-A9) and Qt are best friends when it comes to a great UX. For a volume of one million devices per year, Qt Commercial costs less than 3 Euros per unit (including developer licenses and royalties). A robust, quad-core ARM Cortex-A9 costs roughly 21 Euros per unit, a single-core ARM Cortex-A8 10 Euros and an ARM11 4.50 Euros. If xXx chose Web as its new HMI framework, it would have to use at least a Cortex-A9 for a good-enough UX. With Qt, it could settle for a Cortex-A8. The cost difference per unit would be 11 Euros.

In total, Qt would be at least 8 Euros cheaper per unit than Web. At the given volume, xXx would save 8 million Euros per year when using Qt instead of Web. Even if xXx used Cortex-A8s for Web and ARM11s for Qt, Qt would be 2.50 Euros cheaper per unit and 2.5 million Euros cheaper per year in total than Web.