Our researches are based upon the EPAC project. We develop this work context in our first chapter. Then, transcription task is presented. Some important dates and people are mentionned, as well as an inventory of available speech corpus. Also, assisted and manual transcription task are evaluated and compared. A comparative study of eight transcription tools is developed in the third chapter. It shows that depending on the transcription context (data size, type of annotations ... ), some are more useful than others. Encoding data is the next step of our work. Is it really easy to exchange some transcriptions? We will demonstrate that interoperability must be much more efficient than it currently is, in order to easily share transcribed data. At least, what we name spontaneous speech is precisely analysed. Thanks to several points of view, definitions and experiences, we try to get the precise meaning of this expression.