REPORT Sahidullah_Idiap-RR-14-2019/IDIAP The Speed Submission to DIHARD II: Contributions & Lessons Learned Sahidullah, Md Patino, Jose Cornell, Samuele Yin, Ruiqing Sivasankaran, Sunit Bredin, Herve Korshunov, Pavel Brutti, Alessio Serizel, Romain Vincent, Emmanuel Evans, Nicholas Marcel, Sébastien Squartini, Stefano Barras, Claude diarization DIHARD challenge evaluation single-channel and multi-channel speech EXTERNAL http://publications.idiap.ch/attachments/reports/2019/Sahidullah_Idiap-RR-14-2019.pdf PUBLIC Idiap-RR-14-2019 2019 Idiap November 2019 The paper on arXiv: https://arxiv.org/abs/1911.02388 This paper describes the speaker diarization systems developed for the Second DIHARD Speech Diarization Challenge (DIHARD II) by the Speed team. Besides describing the system, which considerably outperformed the challenge baselines, we also focus on the lessons learned from numerous approaches that we tried for single and multi-channel systems. We present several components of our diarization system, including categorization of domains, speech enhancement, speech activity detection, speaker embeddings, clustering methods, resegmentation, and system fusion. We analyze and discuss the effect of each such component on the overall diarization performance within the realistic settings of the challenge.