# Fit for What Purpose? NER Certification of Automatic Captions in English and Spanish
## 6 Discussion
### The Purpose of Live Captions and the Caption to Transcription Continuum  
Human and automatic live captions are, at least for the time being, two different beasts. When produced by human captioners (stenographers or respekers), live captions are normally edited, that is, they reduce or condense the speech to some extent. The edition or reduction rate varies significantly across countries: from 6-7% in the US [29] to 15% in the UK [13], to as much as 33% in Spain [22]. This condensation is often not intentional but rather imposed upon live captioners, who omit words from the original speech in order to be able to keep up with speakers who can sometimes reach speech rates over 200 and even 250 words per minute. On other occasions, live captioners edit the original speech willingly to make it more readable for the users, i.e., to omit hesitations and repetitions or to introduce punctuation that can help the viewers understand what the speakers are saying. Automatic live captions, in contrast, are normally fully or near verbatim, as shown by the 0.07% edition rate found by [22] in Spain. This means that they are faster than human live captions and that they typically feature almost every word uttered by the speakers, including instances of repetitions, false starts, hesitations, etc. Another difference between human and automatic captions lies in the type of errors and delay they entail. Human live captioners are normally instructed to correct, in real time, those errors that either cause loss of information or distort the original meaning,  
Figure 2: Bar graph of NER accuracy rate scores with assessment of speaker IDs and without assessment of speaker IDs for English (in red) and Spanish subtitles (in blue). that is, standard and serious errors as scored in the NER model. This cannot, however, be done in automatic live captions, which do not benefit from the use of human judgement to decide what error needs to be corrected and how. Also, as shown in this paper, in automatic live captions, the software (without any human help) must decide when a pause corresponds to a comma or full stop or how to tell apart the speech from different speakers. As a result, automatic live captions have so far featured more errors with punctuation marks (particularly full stops, commas and question marks) and speaker ID labels than human live captions [7]. Finally, delay is also another factor that sets apart human and automatic live captions. Respeakers and stenographers need to listen to and process the original speech before they produce their captions, which results in delays that can range from an average of 4-7 s in the UK or the US [20] to 10 s in Spain [22]. This is not an issue for automatic live captions, which typically feature very low delays of 2-3 s.  
Essentially, behind these two types of captions lie two different ideas of what live captions are and what they do, that is, two different purposes. This is illustrated in the \"Caption to Transcription Continuum\" presented below (Figure 3):  
When treated as captions rather than as a transcription, live captions aim to provide an accurate and complete account of what has been said, but completeness may sometimes take a back seat to readability, which is a key priority. Captions are treated as written-like text. If the pressure of the live context allows it, both their content and form are curated, that is, they are edited in order to exclude unnecessary hesitations, mumblings and false starts, and to include punctuation as per written text norms. They are also often condensed, which allows them to keep manageable reading speeds that can enable viewers to both read the captions and look at the speaker or any relevant visual element. Finally, they benefit from human judgement when it comes to deciding which errors should be corrected and how, and they are normally displayed with some delay, which can range from 4-5 s to as much as 10 s. Live captions produced through standard keyboards, Velotype, stenotyping and respeaking are normally close to this side of the continuum.