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# Use Live Mode for Streaming

When you perform speech-to-text conversion on a live audio stream, you can specify a mode that defines the rate to perform analysis. Versions of IDOL Speech Server from 10.8 upwards and the 6.0+ versions of the language packs use DNN acoustic models to improve speech-to-text accuracy. Each language pack contains at least two DNN acoustic models of different sizes. By default, in fixed mode the larger, most accurate model is used.

To override the default option, specify a different DNN file as the value of the `DnnFile` parameter in the task configuration file or at the command line.

Caution: You can use DNN acoustic modelling in live or relative mode only if your DNN files are smaller than a certain size. In addition, you must be using Intel (or compatible) Processors that support SIMD extensions SSSE3 and SSE4.1. If this is not possible, you can set the D`nnFile` parameter to none to allow non-DNN speech-to-text without hardware limitations.

- If you know the rate in advance, use the `relative` mode, which uses a constant rate.

- If the rate varies, use the `live` mode. In `live` mode, recognition keeps pace with the rate at which data is sent to the server.

  - If data is sent to the server in real time, recognition is performed in real time.
  - If data is sent at twice real time, recognition is performed at twice real time, and so on.
  - The rate can change during processing and recognition continues at the correct rate.

  Note: If data streams too fast for the system’s computational resources, recognition accuracy might be impaired.

  Tip: In live or relative mode, it is crucial to ensure that sufficient time is allowed for the recognition process to be robust and to produce transcriptions with good accuracy. To ensure this:

  - There is a limit to the minimum time allowed to perform live or relative recognition, based on the size of the smallest DNN available.
  - IDOL Speech Server monitors how deeply the search is progressing at each point, and sends the results to the speech-to-text diagnostic file at regular intervals. If this file indicates that a search has not had enough time, Speech Server issues a task warning. You can view this warning in the server log file, or retrieve it using the `GetStatus` action. Speech Server repeats the warning after each hour of audio processing.

To use `live` mode in live stream speech-to-text tasks, you must add the `Mode` configuration parameter to the configuration sections for the `stt` and `stream` modules, if it is not already present. For example:

    [stt]
    Mode=$params.Mode

    [stream]
    Mode=$params.Mode

This configuration creates a `Mode` action parameter. To use live mode, set the `Mode` action parameter to `live` in a task action that uses the `stt` and `stream` modules, such as `StreamToText`. For example:

    http://localhost:13000/action=AddTask&Type=StreamToText&Lang=ENUK&Out=Transcript1.ctm&Mode=Live

Related Topics

- Schemas for Standard Tasks

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