fix(elevenlabs): keep transcription word and audio event end at or after start

A word or audio event whose end ElevenLabs sends as a value that is not a finite, non negative number got 0.0 as end even when its start was valid, and a body with an end earlier than its start passed through as is. In both cases srt and vtt rendered a cue that ends before it starts, which players cannot show correctly

end is now the larger of start and the sanitized end, through one helper shared by words and audio events. Valid timestamps with end at or after start are unchanged

Tests cover an unusable or absent end, an end earlier than start and a usable end kept as is for both item types, and check that every srt and vtt cue starts at or before its end, including the malformed timestamps case that used to produce a reversed cue

litellm/llms/elevenlabs/audio_transcription/transformation.py

@@ -47,6 +47,11 @@ def _timestamp(value: object) -> float:
     return seconds
 
 
+def _time_span(item: Mapping[str, object]) -> Mapping[str, float]:
+    start: Final = _timestamp(item.get("start"))
+    return {"start": start, "end": max(start, _timestamp(item.get("end")))}
+
+
 def _speaker_fields(item: Mapping[str, object]) -> Mapping[str, str]:
     speaker: Final = item.get("speaker_id")
     return {"speaker": speaker} if isinstance(speaker, str) else {}
@@ -56,8 +61,7 @@ def _word_fields(item: Mapping[str, object]) -> Mapping[str, object]:
     logprob: Final = _finite_float(item.get("logprob"))
     return {
         "word": item.get("text", ""),
-        "start": _timestamp(item.get("start")),
-        "end": _timestamp(item.get("end")),
+        **_time_span(item),
         **({} if logprob is None else {"logprob": logprob}),
         **_speaker_fields(item),
     }
@@ -66,8 +70,7 @@ def _word_fields(item: Mapping[str, object]) -> Mapping[str, object]:
 def _audio_event_fields(item: Mapping[str, object]) -> Mapping[str, object]:
     return {
         "text": item.get("text", ""),
-        "start": _timestamp(item.get("start")),
-        "end": _timestamp(item.get("end")),
+        **_time_span(item),
         **_speaker_fields(item),
     }
 

tests/unit/llms/elevenlabs/audio_transcription/test_transformation.py

@@ -318,7 +318,7 @@ def test_transform_audio_transcription_response_maps_one_word(
     words: Final = _transform({"text": "t", "words": [word]})["words"]
 
     assert words == expected
-    assert all(isinstance(w[key], float) for w in words for key in ("start", "end"))
+    assert all(isinstance(w["start"], float) and isinstance(w["end"], float) for w in words)
 
 
 @pytest.mark.parametrize("words", [[], "", {}])
@@ -568,6 +568,56 @@ def test_transform_audio_transcription_response_zeroes_absent_start_and_end_and_
     assert item["end"] == 3.0 and isinstance(item["end"], float)
 
 
+@pytest.mark.parametrize("item_type", ["word", "audio_event"])
+@pytest.mark.parametrize("literal", UNUSABLE_TIMESTAMPS)
+def test_transform_audio_transcription_response_ends_at_start_when_end_is_unusable(item_type: str, literal: str):
+    item: Final = _timed_item(_transform_raw(_item_body(item_type, "1.0", literal)), item_type)
+
+    assert item["start"] == 1.0 and item["end"] == 1.0
+    assert isinstance(item["start"], float) and isinstance(item["end"], float)
+
+
+@pytest.mark.parametrize("item_type", ["word", "audio_event"])
+@pytest.mark.parametrize(
+    ("start", "end", "expected_end"),
+    [("1.0", "0.5", 1.0), ("2", "0", 2.0), ("1.0", "1.0", 1.0), ("0.44", "0.68", 0.68), ("1.0", "6.5", 6.5)],
+)
+def test_transform_audio_transcription_response_never_ends_before_it_starts(
+    item_type: str, start: str, end: str, expected_end: float
+):
+    item: Final = _timed_item(_transform_raw(_item_body(item_type, start, end)), item_type)
+
+    assert item["start"] == float(start)
+    assert item["end"] == expected_end
+    assert isinstance(item["end"], float)
+
+
+@pytest.mark.parametrize("item_type", ["word", "audio_event"])
+def test_transform_audio_transcription_response_ends_at_start_when_end_is_absent(item_type: str):
+    body: Final = b'{"words": [{"type": "%s", "text": "x", "start": 1.5}]}' % item_type.encode()
+
+    item: Final = _timed_item(_transform_raw(body), item_type)
+
+    assert item["start"] == 1.5 and item["end"] == 1.5
+
+
+@pytest.mark.parametrize("item_type", ["word", "audio_event"])
+def test_transform_audio_transcription_response_keeps_a_usable_end_when_start_is_unusable(item_type: str):
+    item: Final = _timed_item(_transform_raw(_item_body(item_type, "Infinity", "2.0")), item_type)
+
+    assert item["start"] == 0.0 and item["end"] == 2.0
+
+
+def _cue_seconds(clock: str) -> float:
+    hours, minutes, seconds, millis = (int(part) for part in re.split(r"[:,.]", clock))
+    return hours * 3600 + minutes * 60 + seconds + millis / 1000
+
+
+def _cue_spans(document: str) -> tuple[tuple[float, float], ...]:
+    cues: Final = re.findall(r"(\d{2}:\d{2}:\d{2}[,.]\d{3}) --> (\d{2}:\d{2}:\d{2}[,.]\d{3})", document)
+    return tuple((_cue_seconds(start), _cue_seconds(end)) for start, end in cues)
+
+
 @pytest.mark.parametrize("response_format", SUBTITLE_FORMATS)
 @pytest.mark.parametrize("literal", ["Infinity", "NaN", "1e308", "-Infinity"])
 def test_elevenlabs_transcription_subtitles_survive_unusable_word_timestamps(
@@ -586,6 +636,24 @@ def test_elevenlabs_transcription_subtitles_survive_unusable_word_timestamps(
     assert f"00:00:00{separator}000 --> " in response.text
     assert "Four" in response.text and "score" in response.text
     assert (response_format == "vtt") == response.text.startswith("WEBVTT")
+    spans: Final = _cue_spans(response.text)
+    assert spans
+    assert all(start <= end for start, end in spans)
+
+
+@pytest.mark.parametrize("response_format", SUBTITLE_FORMATS)
+def test_elevenlabs_transcription_subtitles_never_end_before_they_start_when_the_end_is_earlier(
+    response_format: str, respx_mock: respx.MockRouter
+):
+    body: Final = b'{"text": "score", "words": [{"type": "word", "text": "score", "start": 1.0, "end": 0.5}]}'
+
+    response, _ = _transcribe(respx_mock, body, response_format=response_format)
+
+    separator: Final = "," if response_format == "srt" else "."
+    spans: Final = _cue_spans(response.text)
+    assert f"00:00:01{separator}000 --> 00:00:01{separator}000" in response.text
+    assert spans
+    assert all(start <= end for start, end in spans)
 
 
 class TestElevenLabsAudioTranscription: