fix: vtt transcribe not working issue

lib/openai/audio.rb

@@ -5,7 +5,9 @@ def initialize(client:)
     end
 
     def transcribe(parameters: {})
-      @client.multipart_post(path: "/audio/transcriptions", parameters: parameters)
+      plain_text_response = parameters[:response_format] == "vtt"
+      @client.multipart_post(path: "/audio/transcriptions", parameters: parameters,
+                             plain_text_response: plain_text_response)
     end
 
     def translate(parameters: {})

lib/openai/http.rb

@@ -25,8 +25,8 @@ def json_post(path:, parameters:, query_parameters: {})
       end&.body
     end
 
-    def multipart_post(path:, parameters: nil)
-      conn(multipart: true).post(uri(path: path)) do |req|
+    def multipart_post(path:, parameters: nil, plain_text_response: false)
+      conn(multipart: true, plain_text: plain_text_response).post(uri(path: path)) do |req|
         req.headers = headers.merge({ "Content-Type" => "multipart/form-data" })
         req.body = multipart_parameters(parameters)
       end&.body
@@ -71,13 +71,13 @@ def to_json_stream(user_proc:)
       end
     end
 
-    def conn(multipart: false)
+    def conn(multipart: false, plain_text: false)
       connection = Faraday.new do |f|
         f.options[:timeout] = @request_timeout
         f.request(:multipart) if multipart
         f.use MiddlewareErrors if @log_errors
         f.response :raise_error
-        f.response :json
+        f.response :json unless plain_text
       end
 
       @faraday_middleware&.call(connection)

spec/openai/client/audio_spec.rb

@@ -7,23 +7,44 @@
 
         let(:response) do
           OpenAI::Client.new.audio.transcribe(
-            parameters: {
-              model: model,
-              file: File.open(audio, "rb")
-            }
+            parameters: parameters
           )
         end
-        let(:content) { response["text"] }
-        let(:cassette) { "audio #{model} transcribe".downcase }
+        let(:parameters) do
+          {
+            model: model,
+            file: File.open(audio, "rb")
+          }
+        end
 
         context "with model: whisper-1" do
           let(:model) { "whisper-1" }
+          let(:cassette) { "audio #{model} transcribe".downcase }
+          let(:content) { response["text"] }
 
           it "succeeds" do
             VCR.use_cassette(cassette) do
               expect(content.empty?).to eq(false)
             end
           end
+
+          context "with response_format: 'vtt'" do
+            let(:parameters) do
+              {
+                model: model,
+                file: File.open(audio, "rb"),
+                response_format: response_format
+              }
+            end
+            let(:response_format) { "vtt" }
+            let(:cassette) { "audio #{model} transcribe with #{response_format} format".downcase }
+
+            it "succeeds" do
+              VCR.use_cassette(cassette) do
+                expect(response).to include("WEBVTT")
+              end
+            end
+          end
         end
       end
     end