How to send an audio file with an attached thumbnail to Telegram?

Question

Telegram

I'm trying to send an audio file with a thumbnail attached, sendAudio method, thumb parameter .
Everything is successfully delivered to the server, all additional audio parameters are displayed correctly (caption, duration, performer, title) but the thumbnail itself is not displayed in any way. About the limit on the file size and the height-width of the picture in the course, I tried different ones - it is not displayed.
Example:

curl -i -F 'chat_id=<some_id>' \
    -F '[email protected];type=audio/mpeg' \
    -F 'caption=Caption' \
    -F 'duration=100' \
    -F 'performer=Performer' \
    -F 'title=Title' \
    -F '[email protected];type=image/jpeg' \
    'https://api.telegram.org/bot<my_token>/sendAudio'

Has anyone come across what could be wrong?

Answer 1

I will answer myself. The example above actually works.
In the mobile client, the picture is displayed only in the built-in player, as an "icon" of the file.
When choosing a picture, you should also take into account the fact that all the icons in the Telegram are rounded, so square pictures may not look very good.