[Frontend] Add `max-completion-token` option to transcription/translation endpoints (#30769)

Signed-off-by: NickLucche <nlucches@redhat.com>

tests/entrypoints/openai/test_transcription_validation_whisper.py

@@ -244,3 +244,35 @@ async def test_audio_with_timestamp(mary_had_lamb, whisper_client):
     )
     assert transcription.segments is not None
     assert len(transcription.segments) > 0
+
+
+@pytest.mark.asyncio
+async def test_audio_with_max_tokens(whisper_client, mary_had_lamb):
+    transcription = await whisper_client.audio.transcriptions.create(
+        model=MODEL_NAME,
+        file=mary_had_lamb,
+        language="en",
+        response_format="text",
+        temperature=0.0,
+        extra_body={"max_completion_tokens": 1},
+    )
+    out = json.loads(transcription)
+    out_text = out["text"]
+    from transformers import AutoTokenizer
+
+    tok = AutoTokenizer.from_pretrained(MODEL_NAME)
+    out_tokens = tok(out_text, add_special_tokens=False)["input_ids"]
+    assert len(out_tokens) == 1
+    # max_completion_tokens > max_model_len
+    transcription = await whisper_client.audio.transcriptions.create(
+        model=MODEL_NAME,
+        file=mary_had_lamb,
+        language="en",
+        response_format="text",
+        temperature=0.0,
+        extra_body={"max_completion_tokens": int(1e6)},
+    )
+    out = json.loads(transcription)
+    out_text = out["text"]
+    out_tokens = tok(out_text, add_special_tokens=False)["input_ids"]
+    assert len(out_tokens) < 450  # ~Whisper max output len

tests/entrypoints/openai/test_translation_validation.py

@@ -227,3 +227,36 @@ async def test_long_audio_request(foscolo, client_and_model):
     )
     out = json.loads(translation)["text"].strip().lower()
     assert out.count("greek sea") == 2
+
+
+@pytest.mark.asyncio
+async def test_audio_with_max_tokens(mary_had_lamb, client_and_model):
+    client, model_name = client_and_model
+    transcription = await client.audio.translations.create(
+        model=model_name,
+        file=mary_had_lamb,
+        response_format="text",
+        temperature=0.0,
+        extra_body={"max_completion_tokens": 1},
+    )
+    out = json.loads(transcription)
+    out_text = out["text"]
+    print(out_text)
+    from transformers import AutoTokenizer
+
+    tok = AutoTokenizer.from_pretrained(model_name)
+    out_tokens = tok(out_text, add_special_tokens=False)["input_ids"]
+    assert len(out_tokens) == 1
+    # max_completion_tokens > max_model_len
+    transcription = await client.audio.transcriptions.create(
+        model=model_name,
+        file=mary_had_lamb,
+        response_format="text",
+        temperature=0.0,
+        extra_body={"max_completion_tokens": int(1e6)},
+    )
+    out = json.loads(transcription)
+    out_text = out["text"]
+    print(out_text)
+    out_tokens = tok(out_text, add_special_tokens=False)["input_ids"]
+    assert len(out_tokens) < 450  # ~Whisper max output len

vllm/entrypoints/openai/protocol.py

@@ -2054,6 +2054,9 @@ class TranscriptionRequest(OpenAIBaseModel):
 
     presence_penalty: float | None = 0.0
     """The presence penalty to use for sampling."""
+
+    max_completion_tokens: int | None = None
+    """The maximum number of tokens to generate."""
     # --8<-- [end:transcription-sampling-params]
 
     # Default sampling parameters for transcription requests.
@@ -2300,6 +2303,9 @@ class TranslationRequest(OpenAIBaseModel):
     # Flattened stream option to simplify form data.
     stream_include_usage: bool | None = False
     stream_continuous_usage_stats: bool | None = False
+
+    max_completion_tokens: int | None = None
+    """The maximum number of tokens to generate."""
     # --8<-- [end:translation-extra-params]
 
     # Default sampling parameters for translation requests.

vllm/entrypoints/openai/speech_to_text.py

@@ -293,8 +293,14 @@ class OpenAISpeechToText(OpenAIServing):
         try:
             # Unlike most decoder-only models, whisper generation length is not
             # constrained by the size of the input audio, which is mapped to a
-            # fixed-size log-mel-spectogram.
-            default_max_tokens = self.model_config.max_model_len
+            # fixed-size log-mel-spectogram. Still, allow for fewer tokens to be
+            # generated by respecting the extra completion tokens arg.
+            if request.max_completion_tokens is None:
+                default_max_tokens = self.model_config.max_model_len
+            else:
+                default_max_tokens = min(
+                    self.model_config.max_model_len, request.max_completion_tokens
+                )
             sampling_params = request.to_sampling_params(
                 default_max_tokens, self.default_sampling_params
             )