A case study in identifying acceptable bitrates for human face recognition tasks

Face recognition from images or video footage requires a certain level of recorded image quality. This paper derives acceptable bitrates (relating to levels of compression and consequently quality) of footage with human faces, using an industry implementation of the standard H.264/MPEG-4 AVC and the Closed-Circuit Television (CCTV) recording systems on London buses. The London buses application is utilized as a case study for setting up a methodology and implementing suitable data analysis for face recognition from recorded footage, which has been degraded by compression. The majority of CCTV recorders on buses use a proprietary format based on the H.264/MPEG-4 AVC video coding standard, exploiting both spatial and temporal redundancy. Low bitrates are favored in the CCTV industry for saving storage and transmission bandwidth, but they compromise the image usefulness of the recorded imagery. In this context, usefulness is determined by the presence of enough facial information remaining in the compressed image to allow a specialist to recognize a person. The investigation includes four steps: (1) Development of a video dataset representative of typical CCTV bus scenarios. (2) Selection and grouping of video scenes based on local (facial) and global (entire scene) content properties. (3) Psychophysical investigations to identify the key scenes, which are most affected by compression, using an industry implementation of H.264/MPEG-4 AVC. (4) Testing of CCTV recording systems on buses with the key scenes and further psychophysical investigations. The results showed a dependency upon scene content properties. Very dark scenes and scenes with high levels of spatial–temporal busyness were the most challenging to compress, requiring higher bitrates to maintain useful information.

Introduction: resilience and the Anthropocene: the stakes of ‘renaturalising’ politics

The Anthropocene marks a new geological epoch in which human activity (and specifically Western production and consumption practices) has become a geological force. It also profoundly destabilizes the grounds of Western political philosophy. Visions of a dynamic earth system wholly indifferent to human survival liquefy modernity’s division between nature and politics. Critical thought has only begun to scratch the surface of the Anthropocene’s re-naturalization of politics. This special issue of Resilience: International Policies, Practices and Discourses explores the politics of resilience within the wider cultural and political moment of the Anthropocene. It is within the field of resilience thinking that the implications of the Anthropocene for forms of governance are beginning to be sketched out and experimental practices are undertaken. Foregrounding the Anthropocene imaginary’s re-naturalization of politics enables us to consider the political possibilities of resilience from a different angle, one that is irreducible to neoliberal post-political rule.