1541330 - Speech Synthesis play incorrect

Status: NEW

(Core :: Web Speech, defect, P3)

Description

[Karl Dubost💡 :karlcow]

This is https://webcompat.com/issues/27221

and here what the reporter said:

I wrote a simple javascript as below.
when I set lang = 'cmn' (Mandarin Chinese).
it works well in firefox for Android, or Chrome mobile and desktop versions.
however, in firefox desktop version for Ubuntu 18, the speech is unrecognizable.

=========== java script Begin =================
function Sayit() {
let u = new SpeechSynthesisUtterance();
u.lang = 'cmn';
u.text = "早安";
speechSynthesis.speak(u);
}
=========== java script End =================

<details>
<summary>Browser Configuration</summary>
<ul>
<li>None</li>
</ul>

</details>

Reported by @stevene29f

Comment 1

[Firefox Bug Husbandry Bot]

Migrating Webcompat whiteboard priorities to project flags. See bug 1547409.

Comment 2

[Firefox Bug Husbandry Bot]

See bug 1547409. Migrating whiteboard priority tags to program flags.

Comment 3

[C.M.Chang[:chunmin]]

This script doesn't work in both Firefox and Chrome on my OSX.
The problem in Firefox is that we couldn't find a match for lang = cmn. In that case, we will use a locale lang to synthesize voice for speaking.
It can be verified by enabling the log: $ MOZ_LOG="SpeechSynthesis:5" ./mach run. In my case I saw:

[Parent 9252: Main Thread]: D/SpeechSynthesis nsSynthVoiceRegistry::FindBestMatch - Matched UI language (en-US ~= en-US)
[Parent 9252: Main Thread]: D/SpeechSynthesis nsSynthVoiceRegistry::SpeakImpl queueing text='早安' uri='urn:moz-tts:osx:com.apple.speech.synthesis.voice.Alex' rate=1.000000 pitch=1.000000

Chaning the cmn to zh-cmn works for me.

However, it seems that cmn is valid by the spec. cmn should be a valid BCP 47 language tag.

Comment 4

[Mike Taylor [:miketaylr]]

If I run this script in Chrome or Firefox, the result is the same (neither of which sound like Mandarin)...

Comment 5

[Mike Taylor [:miketaylr]]

Andre, what do you think?

Comment 6

[André Natal]

This is a question better suited for Eitan.

Comment 7

[Eitan Isaacson [:eeejay]]

This a Linux platform limitation, not related directly to Firefox. This is why it is reproducible in chrome as well.