1. A method, comprising: defining multiple moderation tasks, which originate from respective textual articles that are to be automatically converted into respective video clips following moderation by human moderators; automatically retrieving a plurality of media assets that contextually match the respective textual article, for each of the defined moderation tasks; pre-processing the moderation tasks so as to predict likelihoods that the human moderators will not reject the moderation tasks, based on a comparison of the moderation tasks to past examples of tasks that passed or failed a moderation stage; and prioritizing delivery of the moderation tasks to the human moderators based on the predicted likelihoods.