Qt for Embedded Linux Hardware Accelerated Graphics

Hardware Acceleration

When designing applications for embedded devices there is often a compromise between graphics effects and performance. On most devices, you cannot have both simply because the hardware needed for such operations just is not there. With a growing number of devices that use hardware dedicated to graphics operations there is less need to compromise.

In addition to enabling dynamic graphics effects, there are two other benefits to using graphics acceleration. One is that graphics acceleration hardware is more power efficient than using the CPU. The reason for this is that the CPU might require a clock speed that is up to 20 times higher than the GPU, achieving the same results. E.g. a typical hardware accelerated mobile graphics unit can rasterize one or two bilinear texture fetches in one cycle, while a software implementation takes easily more than 20 cycles. Typical System-on-a-chip (SoC) graphics hardware generally have a much lower clock speed and memory bandwidth, and different level of acceleration than desktop GPUs. One example is that many GPUs leave out transformation and lighting from the graphics pipeline and only implements rasterization.

Another reason to use a GPU is to offload the main CPU, either for power saving or to perform other operations in parallel. Often drawing speed with a GPU is not that much faster than a CPU but the clear benefit of using the GPU is to free up the CPU to perform other tasks which can be used to create a more responsive use experience.

The key to writing good applications for devices is therefore to limit the wow factor down to what the target hardware can handle, and to take advantage of any graphics dedicated hardware. Qt provides several ways to both render advanced effects on the screen and speed up your application using hardware accelerated graphics.