Unicode Roman Numerals and Screen Readers

How would you read this sentence out aloud?

"In Hamlet, Act Ⅳ, Scene Ⅸ..."

Most people with a grasp of the interplay between English and Latin would say "In Hamlet, Act four, scene nine". And they'd be right! But screen-readers - computer programs which convert text into speech - often get this wrong.

Why? Well, because I didn't just type "Uppercase Letter i, Uppercase Letter v". Instead, I used the Unicode symbol for the Roman numeral 4 - Ⅳ. And, it turns out, lots of screen-readers have a problem with those characters.

Unicode contains the range of Roman numbers from 1 - 10, plus a couple of compound numbers, 50, 100, 500, and 1000 - in a variety of forms.

Why does Unicode contain these number which, to most people, are just squashed together Latin letter? As ever with Unicode, it is a mix of legacy and practicality.

The Unicode standard says:

Roman Numerals. For most purposes, it is preferable to compose the Roman numerals from sequences of the appropriate Latin letters. However, the uppercase and lowercase variants of the Roman numerals through 12, plus L, C, D, and M, have been encoded for compatibility with East Asian standards. Unlike sequences of Latin letters, these symbols remain upright in vertical layout. Additionally, in certain locales, compact date formats use Roman numerals for the month, but may expect the use of a single character.

Far be it for me to disagree with the learned authors of the spec, but I think they may have erred slightly on this one. While it may be preferable to re-use Latin letters, it leads to ambiguity which can be confusing for a screen-reader.

Let's write out the numbers using regular letters. Suppose you were talking about "Romeo and Juliet, Act III, Scene I". Most screen readers will see the "III" and correctly speak aloud "Roman three" or similar. But when they get to the "I" it becomes ambiguous. Most will read out "Eye".

Screen-readers rarely look at the whole sentence for context. Which means they get confused. It's fairly obvious that XIV should be "fourteen" as there's no English word "xiv"¹. But what about "MIX" - is that 1009 or the word "mix"?

Anyone who has watched the BBC knows about their fondness for displaying in Latin the year a programme was made. MCMXCVI is particularly challenging for a screen-reader!

I took the following sample sentence - using both letters and Roman numerals.

Text. In Hamlet, Act I, Scene XI the year is MCMXCVI and they are watching Rocky V.
Roman. In Hamlet, Act Ⅰ, Scene Ⅺ the year is ⅯⅭⅯⅩⅭⅥ and they are watching Rocky Ⅴ.

Here's how various services coped:

First, the good news. Amazon's Polly read the Roman numerals perfectly. It even pronounced ⅯⅭⅯⅩⅭⅥ as "nineteen ninety six".

But it gets rather confused with the ambiguous English text.

I tried with Microsoft Edge's Read Aloud TTS.

It and makes a bit of a hash of the English and just skips the Roman numerals.

The same was also true with Google's TTS products.

The venerable Linux utility came out with this.

It gets the "Capital i" incorrect, and reads the Roman numerals as their Unicode code points.

My good friend Léonie Watson who writes extensively about accessibility was kind enough to record some other samples for me.

Here are Jaws' "Expressive":

And Jaws' "Eloquence:

Léonie also provided a recording of NVDA Microsoft One Core

And here's Narrator making a right mess of it.

If you know of any other screen-readers, or text-to-speech engines which can cope with this, please let me know!

On Linux, I raised a Pull Request to fix espeak-ng.

The rest of the services don't seem to have a way to easily report bugs to them. If you know a way to raise issues with these screen readers - please do so!