Special Session

Information retrieval and multimedia content access have a long history of comparative evaluation, and many of the advances in the area over the past decade can be attributed to the availability of open datasets that support comparative and repeatable experimentation. Sharing data and code to allow other researchers to replicate research results is needed in the multimedia modeling field, as it helps to improve the performance of systems and the reproducibility of published papers.

This report summarizes the special session on Multimedia Datasets for Repeatable Experimentation (MDRE 2019), which was organized at the 25th International Conference on MultiMedia Modeling (MMM 2019), which was held in January 2019 in Thessaloniki, Greece.

The intent of these special sessions is to be a venue for releasing datasets to the multimedia community and discussing dataset related issues. The presentation mode in 2019 was to have short presentations (8 minutes) with some questions, and an additional panel discussion after all the presentations, which was moderated by Björn Þór Jónsson. In the following we summarize the special session, including its talks, questions, and discussions.

The special session presenters: Luca Rossetto, Cathal Gurrin and Minh-Son Dao.

Presentations

A Test Collection for Interactive Lifelog Retrieval

The session started with a presentation about A Test Collection for Interactive Lifelog Retrieval [1], given by Cathal Gurrin from Dublin City University (Ireland). In their work, the authors introduced a new test collection for interactive lifelog retrieval, which consists of multi-modal data from 27 days, comprising nearly 42 thousand images and other personal data (health and activity data; more specifically, heart rate, galvanic skin response, calorie burn, steps, blood pressure, blood glucose levels, human activity, and diet log). The authors argued that, although other lifelog datasets already exist, their dataset is unique in terms of the multi-modal character, and has a reasonable and easily manageable size of 27 consecutive days. Hence, it can also be used for interactive search and provides newcomers with an easy entry into the field. The published dataset has already been used for the Lifelog Search Challenge (LSC) [5] in 2018, which is an annual competition run at the ACM International Conference on Multimedia Retrieval (ICMR).

The discussion about this work started with a question about the plans for the dataset and whether it should be extended over the years, e.g. to increase the challenge of participating in the LSC. However, the problem with public lifelog datasets is the fact that there is a conflict between releasing more content and safeguarding privacy. There is a strong need to anonymize the contained images (e.g. blurring faces and license plates), where the rules and requirements of the EU GDPR regulations make this especially important. However, anonymizing content unfortunately is a very slow process. An alternative to removing and/or masking actual content from the dataset for privacy reasons would be to create artificial datasets (e.g. containing public images or only faces from people who consent to publish), but this would likely also be a non-trivial task. One interesting aspect could be the use of Generative Adversarial Networks (GANs) for the anonymization of faces, for instance by replacing all faces appearing in the content with generated faces learned from a small group of people who gave their consent. Another way to preemptively mitigate the privacy issues could be to wear conspicuous ‘lifelogging stickers’ during recording to make people aware of the presence of the camera, which would give them the possibility to object to being filmed or to avoid being captured altogether.

SEPHLA: Challenges and Opportunities Within Environment-Personal Health Archives

The second presentation was given by Minh-Son Dao from the National Institute of Information and Communications Technology (NICT) in Japan about SEPHLA: Challenges and Opportunities Within Environment-Personal Health Archives [2]. This is a dataset that aims at combining the conditions of the environment with health-related aspects (e.g., pollution or weather data with cardio-respiratory or psychophysiological data). The creation of the dataset was motivated by the fact that people in larger cities in Japan very often do not want to go out (e.g., for some sports activities), because they are very concerned about pollution, i.e., health conditions. So it would be beneficial to have a map of the city with assigned pollution ratings, or a system that allows to perform related queries. Their dataset contains sensor data collected on routes by a few dozen volunteer  people over seven days in Fukuoka, Japan. More particularly, they collected data about the location, O₃, NO₂, PM_2.5 (particulates), temperature, and humidity in combination with heart rate, motion behavior (from 3-axis accelerometer), relaxation level, and other personal perception data from questionnaires.

This dataset has also been used for multimedia benchmark challenges, such as the Lifelogging for Wellbeing task at MediaEval. In order to define the ground truth, volunteers were presented with specific use cases and annotation rules, and were asked to collaboratively annotate the dataset. The collected data (the feelings of participants at different locations) was also visualized using an interactive map. Although the dataset may have some inconsistent annotations, it is easy to filter them out since labels of corresponding annotators and annotator groups are contained in the dataset as well.

V3C – a Research Video Collection

The third presentation was given by Luca Rossetto from the University of Basel (Switzerland) about V3C – a Research Video Collection [3]. This is a large-scale dataset for multimedia retrieval, consisting of nearly 30,000 videos with an overall duration of about 3,800 hours. Although many other video datasets are available already (e.g., IACC.3 [6], or YFCC100M [8]), the V3C dataset is unique in the aspects of timeliness (more recent content than many other datasets and therefore more representative content for current ‘videos in the wild’) and diversity (represents many different genres or use cases), while also having no copyright restrictions (all contained videos were labelled with a Creative Commons license by their uploaders). The videos have been collected from the video sharing platform Vimeo (hence the name ‘Vimeo Creative Commons Collection’ or V3C in short) and represent video data currently used on video sharing platforms. The dataset comes together with a master shot-boundary detection ground truth, as well as keyframes and additional metadata. It is partitioned into three major parts (V3C1, V3C2, and V3C3) to make it more manageable, and it will be used by the TRECVID and the Video Browser Showdown (VBS) evaluation campaigns for several years. Although the dataset was not specifically built for retrieval, it is suitable for any use case that requires a larger video dataset.

The shot-boundary detection used to provide the master-shot reference for the V3C dataset was implemented using Cineast, which is an open source software available for download. It divides every frame into a 3×3 grid and computes color histograms for all 9 areas, which are then concatenated into a ‘regional color histogram’ feature vector that is compared between all adjacent frames. This seems to work very well for hard cuts and gradual transitions, although for grayscale content (and flashlights etc.) it is not very stable. The additional metadata provided with the dataset includes information about resolution, frame rate, uploading user and the upload date, as well as any semantic information provided by the uploader (title, description, tags, etc.). 

Athens Urban Soundscape (ATHUS): A Dataset for Urban Soundscape Quality Recognition

Originally a fourth presentation was scheduled about Athens Urban Soundscape (ATHUS): A Dataset for Urban Soundscape Quality Recognition [4], but unfortunately no author was on site to give the presentation. This dataset contains audio samples with a duration of 30 seconds (as well as extracted features and ground truth) from a metropolitan city (Athens, Greece), that have been recorded during a period of about four years by 10 different persons with the aim to provide a collection about city sounds. The metadata includes geospatial coordinates, timestamp, rating, and tagging of the sound by the recording person. The authors demonstrated in a baseline evaluation that their dataset allows to predict the soundscape quality in the city with about 42% accuracy.

Discussion

After the presentations, Björn Þór Jónsson moderated a panel discussion in which all presenters participated.

The panel started with a discussion on the size of datasets, whether the only way to make challenges more difficult is to keep increasing the dataset, or whether there are alternatives to this. Although this heavily depends on the research question one would like to solve, it was generally agreed that there is a definite need for evaluation with large datasets, because for small datasets some problems are trivial. Moreover, too small datasets often introduce some kind of content bias, so that they do not fully reflect the practical situation.

For now, it seems there is no real alternative to using larger datasets although it is clear that this will introduce additional challenges/hurdles for data management and data processing. All presenters (and the audience too) agreed that introducing larger datasets will also necessitate the need for closer collaboration with other research communities―with fields like data science, data management/engineering, and distributed and high-performance computing―in order to manage the higher data load.

However, even though we need larger datasets, we might not be ready yet to really go for true large-scale. For example, the V3C dataset is still far away from a true web-scale video search dataset; it originally was intended to be even bigger, but there were concerns from the TRECVID and VBS communities about the manageability. Datasets that are too large would set the entrance barrier for newcomers so high that an evaluation benchmark may not attract enough participants―a problem that could possibly disappear in a few years (as hardware becomes cheaper and faster/larger), but still needs to be addressed from an organizational viewpoint. 

There were notes from the audience that instead of focusing on size alone, we should also consider the problem we want to solve. It appears many researchers use datasets for use cases for which they were not designed and are not suited to. Instead of blindly going for larger size, datasets could be kept small and simple for solving essential research questions, for example by truly optimizing them to the problem to solve; different evaluations would then use different datasets. However, this would lead to a considerable dataset fragmentation and necessitate the need for combining several datasets for broader/larger evaluation tasks, which has been shown to be quite challenging in the past. For example, there are already a lot of health datasets available, and it would be interesting to take benefit from them, but the workload for the integration into competitions is often too high in practice.

Another issue that should be addressed more intensively by the research community is to figure out the situation for personal datasets that are compliant with GDPR regulations, since currently nobody really knows how to deal with this.

Acknowledgments

The session was organized by the authors of the report, in collaboration with Duc-Tien Dang-Nguyen (Dublin City University), Michael Riegler (Center for Digitalisation and Engineering & University of Oslo), and Luca Piras (University of Cagliari). The panel format of the special session made the discussions much more lively and interactive than that of a traditional technical session. We would like to thank the presenters and their co-authors for their excellent contributions, as well as the members of the audience who contributed greatly to the session.

References

[1] Gurrin, C., Schoeffmann, K., Joho, H., Munzer, B., Albatal, R., Hopfgartner, F., … & Dang-Nguyen, D. T. (2019, January). A test collection for interactive lifelog retrieval. In International Conference on Multimedia Modeling (pp. 312-324). Springer, Cham.
[2] Sato, T., Dao, M. S., Kuribayashi, K., & Zettsu, K. (2019, January). SEPHLA: Challenges and Opportunities Within Environment-Personal Health Archives. In International Conference on Multimedia Modeling (pp. 325-337). Springer, Cham.
[3] Rossetto, L., Schuldt, H., Awad, G., & Butt, A. A. (2019, January). V3C–A Research Video Collection. In International Conference on Multimedia Modeling (pp. 349-360). Springer, Cham.
[4] Giannakopoulos, T., Orfanidi, M., & Perantonis, S. (2019, January). Athens Urban Soundscape (ATHUS): A Dataset for Urban Soundscape Quality Recognition. In International Conference on Multimedia Modeling (pp. 338-348). Springer, Cham.
[5] Dang-Nguyen, D. T., Schoeffmann, K., & Hurst, W. (2018, June). LSE2018 Panel-Challenges of Lifelog Search and Access. In Proceedings of the 2018 ACM Workshop on The Lifelog Search Challenge (pp. 1-2). ACM.
[6] Awad, G., Butt, A., Curtis, K., Lee, Y., Fiscus, J., Godil, A., … & Kraaij, W. (2018, November). Trecvid 2018: Benchmarking video activity detection, video captioning and matching, video storytelling linking and video search.
[7] Lokoč, J., Kovalčík, G., Münzer, B., Schöffmann, K., Bailer, W., Gasser, R., … & Barthel, K. U. (2019). Interactive search or sequential browsing? a detailed analysis of the video browser showdown 2018. ACM Transactions on Multimedia Computing, Communications, and Applications (TOMM), 15(1), 29.
[8] Kalkowski, S., Schulze, C., Dengel, A., & Borth, D. (2015, October). Real-time analysis and visualization of the YFCC100M dataset. In Proceedings of the 2015 Workshop on Community-Organized Multimodal Mining: Opportunities for Novel Solutions(pp. 25-30). ACM.