Audio src for Google SSML didn't work

does anyone use Google TTS and SSML?
It works well with chromecast binding and Google TTS.

also the tags, like or work well

however i try in vain to play an audio file with the

i try the samples from google sound library but the log says “Audio format OGG_OPUS is not yet supported.” .
So i try also own public downloadable mp3 files
and use samples from

tmptext=tmptext + " The Break worsk fine <break time=\"3s\"/>."
tmptext=tmptext + " <audio src=\"\">Audio not found</audio>"
tmptext=tmptext + " end."

can anyone help me with the sound file?
Thanks in Advance