We introduce a mobile app for collecting in-the-wild data, including sensor measurements and self-reported labels describing people's behavioral context (e.g., driving, eating, in class, shower). Labeled data is necessary for developing context-recognition systems that serve health monitoring, aging care, and more. Acquiring labels without observers is challenging and previous solutions compromised ecological validity, range of behaviors, or amount of data. Our user interface combines past and near-future self-reporting of combinations of relevant context-labels. We deployed the app on the personal smartphones of 60 users and analyzed quantitative data collected in-the-wild and qualitative user-experience reports. The interface's flexibility was important to gain frequent, detailed labels, support diverse behavioral situations, and engage different users: most preferred reporting their past behavior through a daily journal, but some preferred reporting what they're about to do. We integrated insights from this work back into the app, which we make available to researchers for conducting in-the-wild studies.

Digital music has become prolific in the web in recent decades. Automated recommendation systems are essential for users to discover music they love and for artists to reach appropriate audience. When manual annotations and user preference data is lacking (e.g. for new artists) these systems must rely on content based methods. Besides powerful machine learning tools for classification and retrieval, a key component for successful recommendation is the audio content representation. Good representations should capture informative musical patterns in the audio signal of songs. These representations should be concise, to enable efficient (low storage, easy indexing, fast search) management of huge music repositories, and should also be easy and fast to compute, to enable real-time interaction with a user supplying new songs to the system. Before designing new audio features, we explore the usage of traditional local features, while adding a stage of encoding with a pre-computed codebook and a stage of pooling to get compact vectorial representations. We experiment with different encoding methods, namely the LASSO, vector quantization (VQ) and cosine similarity (CS). We evaluate the representations' quality in two music information retrieval applications: query-by-tag and query-by-example. Our results show that concise representations can be used for successful performance in both applications. We recommend using top- τ VQ encoding, which consistently performs well in both applications, and requires much less computation time than the LASSO.