Error 429 on Audio export from Azure Text to Speech (Audio Creation Tool)

Question

Hello experts.
This is about Cognitive Services → Audio Content Creator → Text to Speech.
I'm testing this environment for my organization, so we're on the Free tier.

The issue:
I have a file in German with a Neural Voice and a Lexicon loaded.
When exporting the audio by separate phrases (47), the resulting file contains less than 47. When trying several times, the number varies, but it doesnt reach 47.
This is strange because the export has been working perfectly for months. Why the change now?

I get this error message:
"Error 429. Requests to the TTS synthesis API for all ACC voices.
Operation under AC API v3.0-beta1 have exceeded the rate limit of your current speech services F0 pricing tier.
Please try after 50seconds. To increase your rate limit switch to a paid tier

Connection ID 16f6752a-8f7c-11ec-85db-cdc25787aca1"

Why do I have to pay to export now? This is very strange.

Answer 1

@Hector SOLANO The free tier usually has a very low concurrent request limit(1) which in some cases could result in this error if you have tried too many requests at a time.
The issue should not be with the quota limit of characters as you have mentioned the no. of characters are quite low unless you do not exceed the monthly quota.

For the error code 429 the most likely cause could be the following, which is also documented here, You can retry later and check if the export is successful.

Suppose that your application receives response code 429, which indicates that there are too many requests. Your application receives this response even though your workload is within the limits defined by the Quotas and limits reference. The most likely explanation is that Speech service is scaling up to your demand and didn't reach the required scale yet. Therefore the service doesn't immediately have enough resources to serve the request. In most cases, this throttled state is transient.

For some cases even in paid tier if the above error message is seen then customers can request limit increase for certain quotas for their resource in their subscription with valid business reason. This can be done by using the support case from Azure portal.

I hope this helps!!

If an answer is helpful, please click on or upvote which might help other community members reading this thread.