Processing digital radio - either on the transmitter or the receiver side - requires a significant amount of digital processing. A receiver for digital radio usually consists of two parts, a ”hardware” part, handling the conversion from an analog antenna signal to a stream samples, and a ”software part”, a decoder, decoding the samples and generating audio, text, images and video. In this paper some aspects of the design and implementation of Qt-DAB, a software decoder for Digital Audio Broadcasting (DAB and DAB+), is discussed. The Qt-DAB decoder runs on a variety of hardware platforms, hardware as small as creditcard sized computers as the Raspberry PI 2, and home computers. In the design performance and flexibility were key. The design is such that it is easy to interface to different hardware SDR devices and easy to add new features. While the core of the Qt-DAB software is formed by the signal processing part, interpreting the incoming sample stream and generating audio, text and images, by far the largest part of the software is handling user interaction and user comfort. Qt-DAB provides a large amount of options, options to select a device, to inspect the signal, to store signals, and options to set the configuration. All in all, it shows that about three quarters of the amount of code is involved is the non signal processing part.