[FFmpeg-user] ffmpeg/ffprobe won't detect the language of a webvvt (subtitles) file

[pehache]

Hello,

A webtt subtitles files starts with a few header lines, and one of them 
indicates the language:

==================================
WEBVTT
Kind: captions
Language: en
==================================

But ffmpeg won't detect the language. The ffprobe output on the above 
file makes no mention of it:

==================================
Input #0, webvtt, from 'Star Trek Continues E01 ＂Pilgrim of Eternity＂ 
[3G-ziTBAkbQ].en.vtt':
   Duration: N/A, bitrate: N/A
   Stream #0:0: Subtitle: webvtt
==================================

Consequentely, when muxed into a video file, no language is reported for 
the subtitle streams.

In constrast, MKVToolnix detects the language when reading a webvtt file 
(although not always perfectly)

Is there a simple solution? I know it's possible to force a langage for 
any stream, but in practice for each video file I have many subtitle 
tracks to mux, and this is handled by scripts, so I'd prefer something 
straigth and automatic.