Use verbose Whisper transcription output

internal/transcription/client.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"mime/multipart"
@@ -103,6 +104,15 @@ type audioTranscriptionSegment struct {
 	Text  string  `json:"text"`
 }
 
+type audioTranscriptionStatusError struct {
+	status int
+	body   string
+}
+
+func (e audioTranscriptionStatusError) Error() string {
+	return fmt.Sprintf("audio transcription HTTP %d: %s", e.status, e.body)
+}
+
 func New(baseURL string, timeout time.Duration, ffmpegPath string, leadSilence time.Duration) *Client {
 	return NewWithOptions(Options{
 		AudioBaseURL: baseURL,
@@ -233,7 +243,15 @@ func clampTime(v float64) float64 {
 }
 
 func (c *Client) transcribeOpenAIAudio(ctx context.Context, provider ProviderConfig, audio []byte, filename string, in Input) (*audioLLMResponse, time.Duration, error) {
-	return c.doOpenAIAudioTranscription(ctx, provider, audio, filename, in, "json")
+	resp, duration, err := c.doOpenAIAudioTranscription(ctx, provider, audio, filename, in, "verbose_json")
+	if err == nil {
+		return resp, duration, nil
+	}
+	if !isVerboseJSONUnsupported(err) {
+		return nil, duration, err
+	}
+	fallbackResp, fallbackDuration, fallbackErr := c.doOpenAIAudioTranscription(ctx, provider, audio, filename, in, "json")
+	return fallbackResp, duration + fallbackDuration, fallbackErr
 }
 
 func (c *Client) doOpenAIAudioTranscription(ctx context.Context, provider ProviderConfig, audio []byte, filename string, in Input, responseFormat string) (*audioLLMResponse, time.Duration, error) {
@@ -295,7 +313,7 @@ func (c *Client) doOpenAIAudioTranscription(ctx context.Context, provider Provid
 		return nil, duration, fmt.Errorf("audio transcription read: %w", err)
 	}
 	if resp.StatusCode >= 300 {
-		return nil, duration, fmt.Errorf("audio transcription HTTP %d: %s", resp.StatusCode, strings.TrimSpace(string(raw)))
+		return nil, duration, audioTranscriptionStatusError{status: resp.StatusCode, body: strings.TrimSpace(string(raw))}
 	}
 	var out audioTranscriptionResponse
 	if err := json.Unmarshal(raw, &out); err != nil {
@@ -313,6 +331,20 @@ func (c *Client) doOpenAIAudioTranscription(ctx context.Context, provider Provid
 	}, duration, nil
 }
 
+func isVerboseJSONUnsupported(err error) bool {
+	var statusErr audioTranscriptionStatusError
+	if !errors.As(err, &statusErr) {
+		return false
+	}
+	if statusErr.status != http.StatusBadRequest && statusErr.status != http.StatusUnprocessableEntity {
+		return false
+	}
+	body := strings.ToLower(statusErr.body)
+	return strings.Contains(body, "verbose_json") ||
+		strings.Contains(body, "response_format") ||
+		strings.Contains(body, "timestamp_granularities")
+}
+
 func convertAudioSegments(in []audioTranscriptionSegment) []Segment {
 	out := make([]Segment, 0, len(in))
 	for _, s := range in {

internal/transcription/client_test.go

@@ -28,7 +28,7 @@ func TestWhisperUsesAudioTranscriptionsEndpoint(t *testing.T) {
 	}))
 	defer audioSrv.Close()
 
-	var gotPath, gotModel, gotResponseFormat, gotPrompt, gotTemperature string
+	var gotPath, gotModel, gotResponseFormat, gotPrompt, gotTemperature, gotTimestampGranularity string
 	providerSrv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		gotPath = r.URL.Path
 		if err := r.ParseMultipartForm(16 << 20); err != nil {
@@ -38,6 +38,7 @@ func TestWhisperUsesAudioTranscriptionsEndpoint(t *testing.T) {
 		gotResponseFormat = r.FormValue("response_format")
 		gotPrompt = r.FormValue("prompt")
 		gotTemperature = r.FormValue("temperature")
+		gotTimestampGranularity = r.FormValue("timestamp_granularities[]")
 		if _, _, err := r.FormFile("file"); err != nil {
 			t.Fatalf("FormFile: %v", err)
 		}
@@ -68,12 +69,15 @@ func TestWhisperUsesAudioTranscriptionsEndpoint(t *testing.T) {
 	if gotModel != "openai/whisper-large-v3" {
 		t.Fatalf("model = %q", gotModel)
 	}
-	if gotResponseFormat != "json" {
-		t.Fatalf("response_format = %q, want json", gotResponseFormat)
+	if gotResponseFormat != "verbose_json" {
+		t.Fatalf("response_format = %q, want verbose_json", gotResponseFormat)
 	}
 	if gotTemperature != "0" {
 		t.Fatalf("temperature = %q, want 0", gotTemperature)
 	}
+	if gotTimestampGranularity != "segment" {
+		t.Fatalf("timestamp_granularities[] = %q, want segment", gotTimestampGranularity)
+	}
 	if gotPrompt != "" {
 		t.Fatalf("prompt = %q, want empty", gotPrompt)
 	}
@@ -82,6 +86,48 @@ func TestWhisperUsesAudioTranscriptionsEndpoint(t *testing.T) {
 	}
 }
 
+func TestWhisperFallsBackToJSONWhenVerboseJSONUnsupported(t *testing.T) {
+	audioSrv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte("fake audio"))
+	}))
+	defer audioSrv.Close()
+
+	var formats []string
+	providerSrv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if err := r.ParseMultipartForm(16 << 20); err != nil {
+			t.Fatalf("ParseMultipartForm: %v", err)
+		}
+		format := r.FormValue("response_format")
+		formats = append(formats, format)
+		if format == "verbose_json" {
+			w.WriteHeader(http.StatusBadRequest)
+			_ = json.NewEncoder(w).Encode(map[string]any{
+				"error": map[string]any{"message": "unsupported response_format verbose_json"},
+			})
+			return
+		}
+		_ = json.NewEncoder(w).Encode(map[string]any{
+			"text": "Алло, fallback работает.",
+		})
+	}))
+	defer providerSrv.Close()
+
+	client := NewWithOptions(Options{
+		AudioBaseURL: providerSrv.URL,
+		AudioModel:   "openai/whisper-large-v3",
+	})
+	got, err := client.Transcribe(t.Context(), Input{AudioURL: audioSrv.URL, Filename: "call.mp3"})
+	if err != nil {
+		t.Fatalf("Transcribe: %v", err)
+	}
+	if len(formats) != 2 || formats[0] != "verbose_json" || formats[1] != "json" {
+		t.Fatalf("formats = %#v, want verbose_json then json", formats)
+	}
+	if got.Segments[0].Text != "Алло, fallback работает." {
+		t.Fatalf("segments = %#v", got.Segments)
+	}
+}
+
 func TestSegmentTranscriptTextDoesNotInventSpeakers(t *testing.T) {
 	got := segmentTranscriptText("Алло, добрый день. Да, слушаю. Скажите, квартира продается? Да, продается.")
 	if len(got) < 2 {