Translating a curl command to R using httr (specifically '--data-binary @')

I am trying to transcribe some sound files to text using bing speech-to-text.

The following command works in command line (using git bash on Windows 10):

curl  -v -X POST "https://speech.platform.bing.com/speech/recognition/interactive/
cognitiveservices/v1?language=<LANG>&format=detailed" -H "Transfer-Encoding: 
chunked" -H "Ocp-Apim-Subscription-Key: <MY KEY>" -H "Content-type: 
audio/wav; codec=audio/pcm; samplerate=16000" --data-binary @<MY .WAV-FILE>

I've tried this, but it doesnt work:

httr::POST(url = myURL,
           add_headers("Ocp-Apim-Subscription-Key" = key,
                       "Content-type" = "audio/wav; codec=audio/pcm; samplerate=16000",
                       "Transfer-Encoding" = "chunked"),
           body = (list("file" = upload_file("PATH_TO_FILE.wav"))),
           verbose())

It returns this output: Response

[https://speech.platform.bing.com/speech/recognition/dictation/
cognitiveservices/v1?language=<LANG>&format=detailed]
Date: 2017-11-29 13:29
Status: 200
Content-Type: text/plain
Size: 75 B

I believe that the request is related to the interpretation of the .wav file, and that I need to somehow add the '--data-binary' tag to the httr-request. I can see that my "content-type" is plain text, although i've specified. Furthermore: the API documentation specifies that i need to prefix my wav-file with an at-sign.

Any help would be much appreciated.

cheers.

EDIT: Link to API documentation https://learn.microsoft.com/da-dk/azure/cognitive-services/speech/getstarted/getstartedrest?tabs=curl#tabpanel_AFC9x30-dR_curl

Solution

I figured it out.

The key is to set the proper MIME type in the body. Not setting this MIME type can result in wrongful interpretation on the receiving end, even though we get a response 200 back.

body <- list(file = httr::upload_file(
  paste0(path, "/", f),
  type = "audio/wav; codec=audio/pcm; samplerate=16000"))

where paste0(path, "/", f) is a path to an audio file.

myURL <- sprintf('https://speech.platform.bing.com/speech/recognition/%s/cognitiveservices/v1?language=%s&format=%s',
"dictation",
"da-DK",
"detailed")

rs <- httr::POST(
  url = myURL,
  httr::add_headers(.headers = c("Ocp-Apim-Subscription-Key" = key)),
  httr::add_headers(.headers = c("Transfer-Encoding" = "chunked")),
  body = body)