IBM Watson speech-to-text converter for Knative

Converts audio payload to text, using IBM Watson Speech to Text.

Input

Cloud event:

• Data Content Type: Mime type of the audio payload (e.g. audio/wav)
• Payload: Binary audio payload in the type specified by data content type

Output

The output event will contain all information of the input event, with the following changes:

• Data Content Type: application/json
• Data Schema: https://cloud.ibm.com/services/speech-to-text/v1/recognize
• Payload: Response JSON, with recognized text.

Payload

The payload must be an accepted audio format (with a matching mime type in the data content type). You can find more information about that in the section Audio Formats of IBM Watson.

Of course, there is a special case. There are two different mime types for WAV files (audio/wav and audio/vnd.wav). Watson accepts only audio/wav. If you have audio/vnd.wav, you need to convert that first. However, the converter can do that for you if FIX_WAV_TYPE is set to true (which is the default).

So if your content type is e.g. audio/vnd.wav; codec=1, it will automatically translated into audio/wav unless you explicitly disable the logic by setting FIX_WAV_TYPE=false.

Installation

See deploy/ for information how to install.

Configuration

You can use the following environment variables to configure its behavior:

Name	Default	Description
BIND_ADDR	127.0.0.1:8080	The address the HTTP server binds to
RUST_LOG	none	The configuration of the logger, also see https://docs.rs/env_logger/latest/env_logger/
CREDENTIALS_PATH	/etc/config/credentials.json	The path to the credential file
ONLY_TYPES	none	A comma separated list of allowed types. If the list is empty the filter will not be applied and the event will pass.
ONLY_SUBJECTS	none	A comma separated list of allowed subjects. If the list is empty the filter will not be applied and the event will pass.
ONLY_DATACONTENTTYPES	none	A comma separated list of allowed data content types. If the list is empty the filter will not be applied and the event will pass.
FIX_WAV_TYPE	true	Enable fixing of WAV content type (see section #payload)

Filter

A filter can be applied to incoming events. Events that do not match the filter criteria are discarded. In a nutshell, the filter requires all criteria to pass, an empty filter configuration automatically passes.