1. A speech media transcription system comprising a playback device arranged to play back speech delimited in segments, the system being programmed: to play back an entire segment for a transcriber to transcribe; to estimate a limit of a working memory of the transcriber; to provide, for a segment being transcribed, an adaptive estimate of the proportion of the segment that has not been transcribed by the transcriber; and subsequently to play back again said proportion of the segment that has not been transcribed, immediately when the adaptive estimate indicates that a current playback position is exceeding the limit of the working memory of the transcriber.