Abstract: A service for generating textual transcriptions of video content is provided. A textual output generation service utilize machine learning techniques provide additional context for textual transcription. The textual output generation service first utilizes a machine learning algorithm to analyze video data from the video content and identify a set of context keywords corresponding to items identified in the video data. The textual output generation service then identifies one or more custom dictionaries of relevant terms based on the identified keywords. The textual output generation service can then utilize a machine learning algorithm to process the audio data from the video content biased with the selected dictionaries. The processing result can be utilized used to generate closed captioning information, textual content streams or otherwise stored.