This paper presents novel results concerning engagement with ICT standards and their implementations in open source software (OSS). Specifically, findings draw from observations and analysis related to standards and implementations in the multimedia field. The first part of the study reports on experiences and insights from engagement with standards in the multimedia field and from implementation of such standards in OSS projects. The second part of the study focuses on the case of the ITU-T H.264 standard and the two OSS projects OpenH264 and x264 that both implement the standard, and reports on a characterisation of organisations that engage with and control the H.264 standard, and organisations that engage with and control OSS projects implementing the H.264 standard. Further, projects for standardisation and implementation of H.264 are contrasted with respect to mix of contributing organisations, and findings are related to organisational strategies of contributing organisations and previous research.