Speech synthesis: building a voice, one language at a time
Speech synthesis turns text into audio. Building it for a language needs a voice, licensed and recorded, which is why a list of languages a tool can speak is structurally shorter than a list of the languages it can hear. As of 2026-09-22.
| Requirement | Speech synthesis | Speech recognition |
|---|---|---|
| Training material | A voice recorded for the purpose | Recordings of people talking |
| Licensing | Per voice, and negotiated | Rarely per speaker |
| Cost of adding a language | High | Lower |
| Typical inventory size | Smaller | Larger |
Inclusion rule. The two directions of a dubbing pipeline, compared on what adding a language to each one requires. Order. Fixed order, the requirement that differs most first.
1A voice has to be built and paid for
Recognising speech can be trained from material that already exists in quantity. Producing it needs a voice recorded for that purpose, with a contract behind it, per language and often per variety.
So the asymmetry between the two sides of a dubbing product is structural rather than a gap somebody forgot to close. Every vendor selling dubbing has it, whether or not its pages show it.
2One vendor here publishes both sides
A single vendor in this register prints two lists, one of the languages it can detect in a source file and a shorter one of the languages it can dub into. The difference is more than forty languages.
That vendor is not unusual in having the gap; it is unusual in showing it. Every other spoken-language figure here is one-sided, and a reader cannot tell which side of the pipeline it describes.
3Which side a figure describes changes what it is worth
A figure describing recognition tells a buyer what material they can bring. A figure describing synthesis tells them which markets they can reach. Only the second one has revenue attached to it.
When a vendor publishes one number and no direction, this register records the wording rather than guessing which side it belongs to. The wording is usually the only clue, and sometimes there is none.
A definition, not a measurement: no vendor figure appears here that is not also in the register. The one two-sided list in this register is recorded on that vendor cell.
Nearby terms: Voice inventory, Speech recognition. The whole vocabulary is at terms; nothing on this page is a claim about a named product.