Lecture Transcription A Whole Semester You Can Search

What changes when a lecture becomes text

A recorded lecture is only useful if you are willing to listen to it again at the same speed it was given. A transcript changes that. You can read ninety minutes in twenty, jump straight to the part where the derivation was explained, and search a whole semester of lectures for the one time the lecturer mentioned the term that is now on the exam paper. Revision stops being a question of where in which recording something was said.

For students who need text to follow a class, whether because of a hearing impairment, a language barrier or a processing difference, a transcript is the difference between taking part and falling behind. Lecturers who publish transcripts alongside recordings also find that questions about what was said in a lecture drop sharply, because students can check for themselves.

Recordings from phones, capture systems and YouTube

Most lecture recordings come from one of three places. A phone on the desk produces an M4A or MP3 file that picks up the lecturer well if the room is not too big. Lecture-capture systems such as Panopto, Echo360 or a Zoom classroom produce an MP4 with slides and voice, which is uploaded as it is; the video track is simply ignored. Lectures published on YouTube, including whole open courses, can be transcribed from the link without downloading anything.

A lecture is a good case for speech recognition because one person speaks for most of the time. The output comes out as continuous, clean paragraphs with a timestamp at the start of each one, rather than the fragmented dialogue of a meeting. Questions from the audience are usually quieter and further from the microphone, so they may be partly missed; the lecturer repeating the question, as many do, solves that.

Technical vocabulary and the editor

Speech recognition handles everyday language very well and specialised terms reasonably well. Names of theorems, drug names, legal cases, chemical compounds and anything the lecturer pronounces in a hurry are the places where a transcript may need a correction. With a free account the editor lets you fix a term once and find every other occurrence with the built-in search, which takes a few minutes for a full lecture.

The language is detected automatically and more than fifty languages are supported, so lectures given in German, French, Spanish or Polish, or a lecture in English with quotations in another language, are handled without settings.

Long lectures and recordings that stay private

The free limit is 3 hours per recording, which covers a double lecture or a full-day seminar in a single upload. Processing takes about three to five minutes per hour of audio because the file is split into segments that run in parallel. The speech models run on our own servers and the recording is not forwarded to a third-party speech API, which is worth knowing when a lecture includes discussion of unpublished research or student work. Transcriptions made here without an account move into a free account if you create one later.