Rate this page:

Speech recognition

You can recognize live speech during an active call or conference.

Contents

Copy URL

There are two modes of speech recognition in Voximplant. The Phrase hint mode recognizes user input from the list of preset phrases and can be useful in IVRs and dialogs with voice interaction. The Freeform mode recognizes all the user input and transcribes it to text, which can be useful in transcribing human conversation into text file.

You can use various speech recognition engines such as Google, Amazon, Microsoft, Yandex or Tinkoff. You can find the profile names here.

Please note

The Phrase hint mode is supported by Google profile only. Google do not limit the results to the specified list, but the words in the list you specify have higher chance to be selected.

How to use speech recognition

Copy URL
  1. Import ASR module into your scenario via the require method:
require(Modules.ASR)
  1. Use the VoxEngine.createASR method to create an ASR object.
  2. Subscribe to the ASR object events like ASREvents.Result.
  3. Send media from a call object to the ASR object via the sendMediaTo method
  4. Receive the results via events

If you want to use the Phrase hint mode for speech recognition, specify the phraseHints parameter after the speech recognition profile. See the following code example to understand how it works:

ASR with hints

ASR with hints

Please note

The Phrase hint mode is supported by Google profile only.

If you want to use the Freeform mode, the Result event triggers every time the voice is recognized. There is always a delay between capture and recognition, so plan user interaction accordingly.

Use the following code example to understand how this mode works:

ASR without hints

ASR without hints

How to transcribe a call

Copy URL

Use the record method to transcribe a call or a conference into a text file. Set the transcribe parameter to true and the language parameter to one of the supported languages.

See the following code example to understand how it works:

Transcribe a call

Transcribe a call

Unlike audio and video recording, transcription results are available only after a call ends, so it should be retrieved via the GetCallHistory method of the HTTP API. You have to call this method with the with_records=true parameter specified.

There are records in the response JSON with the transcription_url field. This field value returns the transcription as a plain text:

GetCallHistory

GetCallHistory

Each line in transcription file is prefixed "Left" for an audio stream from a call endpoint to the Voximplant cloud, and "Right" for an audio stream from the Voximplant cloud to a call endpoint (same logic as with left and right audio channel for stereo recording).

"Left" and "Right" names can be changed via the labels parameter. The dict parameter allows you to specify an array of words that the transcriber tries to match in case of recognition problems. Specifying domain-specific words can improve transcription results a lot.

How to use Google's beta STT features

Copy URL

Since Google provides access to their Speech API v1p1beta1 features, we support it as well.

Currently, Voximplant speech recognition supports the following features:

  • enableSeparateRecognitionPerChannel

  • alternativeLanguageCodes

  • enableWordTimeOffsets

  • enableWordConfidence

  • enableAutomaticPunctuation

  • diarizationConfig

  • metadata

To use the features, you have to set the beta parameter to true when creating an ASR instance:

ASR Instance with v1p1beta1

ASR Instance with v1p1beta1

Refer to the API reference to learn about the parameters.

Here is what the request's result looks like:

ASR result

ASR result

With Google beta features, the ASREvents.result event updates with the resultEndTime, channelTag, and languageCode properties. You can see them in the session logs.