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Table 1. Advanced Parameters





false (default), true

Specifies that the input file is encoded in base 64.


The value specified is the name or number of the billing account that a transcription request should be associated with.


false (default), true, language_model

The lid parameter enables you to use the ASR engine's Language Identification (LID) module to identify the language spoken in the input audio and automatically use an appropriate language model. To force the use of an an alternate model with a different "domain" name, specify it using lid=language_model.

Refer to lid for additional parameters and information.


true (default), false, md5

Available with V‑Cloud 1.6+

The filemd5 parameter enables or disables MD5 verification of audio data.

  • filemd5=true - Default value of filemd5. Setting the value to true enables MD5 verification if possible.

  • filemd5=false - Setting the value to false disables MD5 verification. Disabling MD5 verification is useful for audio data that includes Content-MD5 or ETag headers that don't specify any MD5 for the audio data.

  • filemd5=user-specified-md5 - Enables MD5 verification by specifying a 32 hexadecimal digit value to use for verification.



The metadata parameter enables the inclusion of user-defined metadata in a top-level object in JSON transcripts. Specify a string as the value of metadata in your request as shown in the following example:

curl -F file=@sample.wav \ 
     -F token=token \
     -F metadata=sample metadata string \

As a result, the metadata specified in the request above is included in the JSON transcripts:

"streamtags": {
        "metadata": "sample metadata string",
        "model": "eng1:callcenter"


The metadata parameter does not have any effect on the transcription process. It is used to include extraneous information in a transcription request and pass that custom data to a V‑Cloud callback.