Hi @zhongshun ,
Welcome to Google Cloud Community!
You are correct that Google Cloud Speech-to-Text does not support transcribing audio with mixed-language content. Alternatively, you might consider submitting a feature request for mixed language inputs in Speech-to-Text. While I can’t provide a timeline for when this enhancement might be available, I recommend keeping an eye on the issue tracker and checking the release notes for the latest updates.
I hope the above information is helpful.