[whisper] alternative fix for long-form timestamps (huggingface#32131)

* [whisper] alternative fix for long-form timestamps

* update test

src/transformers/models/whisper/tokenization_whisper.py

@@ -587,11 +587,20 @@ def _compute_offsets(self, token_ids, time_precision=0.02):
             consecutive = np.append(consecutive, np.where(timestamp_tokens)[0][-1] + 1)
 
         last_slice = np.where(timestamp_tokens)[0][0]
+        cur_max_timestamp = 0
+        prev_segments_len = 0
         for current_slice in consecutive:
             sliced_tokens = token_ids[last_slice:current_slice]
             if len(sliced_tokens) > 1:
                 start_timestamp_position = sliced_tokens[0].item() - timestamp_begin
                 end_timestamp_position = sliced_tokens[-1].item() - timestamp_begin
+
+                if start_timestamp_position < cur_max_timestamp:
+                    # next segment has started
+                    prev_segments_len += cur_max_timestamp
+
+                cur_max_timestamp = end_timestamp_position
+
                 # strip timestamp tokens from the text output
                 sliced_tokens = self._preprocess_token_ids(sliced_tokens)
                 text = self._decode(sliced_tokens)
@@ -600,8 +609,8 @@ def _compute_offsets(self, token_ids, time_precision=0.02):
                     {
                         "text": text,
                         "timestamp": (
-                            start_timestamp_position * time_precision,
-                            end_timestamp_position * time_precision,
+                            (start_timestamp_position + prev_segments_len) * time_precision,
+                            (end_timestamp_position + prev_segments_len) * time_precision,
                         ),
                     }
                 )

src/transformers/models/whisper/tokenization_whisper_fast.py

@@ -229,11 +229,20 @@ def _compute_offsets(self, token_ids, time_precision=0.02):
             consecutive = np.append(consecutive, np.where(timestamp_tokens)[0][-1] + 1)
 
         last_slice = np.where(timestamp_tokens)[0][0]
+        cur_max_timestamp = 0
+        prev_segments_len = 0
         for current_slice in consecutive:
             sliced_tokens = token_ids[last_slice:current_slice]
             if len(sliced_tokens) > 1:
                 start_timestamp_position = sliced_tokens[0].item() - timestamp_begin
                 end_timestamp_position = sliced_tokens[-1].item() - timestamp_begin
+
+                if start_timestamp_position < cur_max_timestamp:
+                    # next segment has started
+                    prev_segments_len += cur_max_timestamp
+
+                cur_max_timestamp = end_timestamp_position
+
                 # strip timestamp tokens from the text output
                 sliced_tokens = self._preprocess_token_ids(sliced_tokens)
                 text = self._decode(sliced_tokens)
@@ -242,8 +251,8 @@ def _compute_offsets(self, token_ids, time_precision=0.02):
                     {
                         "text": text,
                         "timestamp": (
-                            start_timestamp_position * time_precision,
-                            end_timestamp_position * time_precision,
+                            (start_timestamp_position + prev_segments_len) * time_precision,
+                            (end_timestamp_position + prev_segments_len) * time_precision,
                         ),
                     }
                 )

tests/models/whisper/test_modeling_whisper.py

@@ -2099,6 +2099,65 @@ def test_tiny_timestamp_generation(self):
         transcript = processor.batch_decode(generated_ids, skip_special_tokens=True, output_offsets=True)
         self.assertEqual(transcript, EXPECTED_TRANSCRIPT)
 
+    @slow
+    def test_tiny_longform_timestamps_generation(self):
+        set_seed(0)
+        processor = WhisperProcessor.from_pretrained("openai/whisper-tiny")
+        model = WhisperForConditionalGeneration.from_pretrained("openai/whisper-tiny")
+        model.to(torch_device)
+
+        dataset = load_dataset("distil-whisper/librispeech_long", "clean", split="validation")
+        sample = dataset[0]["audio"]
+
+        input_features = processor(
+            sample["array"], return_tensors="pt", truncation=False, sampling_rate=sample["sampling_rate"]
+        )
+        input_features = input_features.to(torch_device)
+
+        generated_ids = model.generate(**input_features, return_timestamps=True, return_segments=True)
+
+        EXPECTED_TRANSCRIPT = [
+            {
+                "text": " Mr. Quilter is the apostle of the middle classes, and we are glad to welcome his gospel.",
+                "timestamp": (0.0, 6.5600000000000005),
+            },
+            {
+                "text": " Nor is Mr. Quilter's manner less interesting than his matter.",
+                "timestamp": (6.5600000000000005, 11.24),
+            },
+            {
+                "text": " He tells us that at this festive season of the year, with Christmas and roast beef looming",
+                "timestamp": (11.24, 16.88),
+            },
+            {
+                "text": " before us, similarly drawn from eating and its results occur most readily to the mind.",
+                "timestamp": (16.88, 23.76),
+            },
+            {
+                "text": " He has grave doubts whether Sir Frederick Latins' work is really Greek after all, and",
+                "timestamp": (23.76, 29.44),
+            },
+            {"text": " can discover in it but little of rocky ithaka.", "timestamp": (29.44, 33.72)},
+            {
+                "text": " Lennils, pictures, are a sort of upguards and atom paintings, and Mason's exquisite itals",
+                "timestamp": (33.72, 40.32),
+            },
+            {"text": " are as national as a jingo poem.", "timestamp": (40.32, 44.72)},
+            {
+                "text": " Mr. Birkut Foster's landscapes smile at one much in the same way that Mr. Carker used",
+                "timestamp": (44.72, 50.4),
+            },
+            {"text": " to flash his teeth.", "timestamp": (50.4, 52.96)},
+            {
+                "text": " And Mr. John Collier gives his sitter a cheerful slap on the back before he says, like",
+                "timestamp": (52.96, 58.68),
+            },
+            {"text": " a shampoo and a Turkish bath next man.", "timestamp": (58.68, 61.96)},
+        ]
+
+        transcript = processor.batch_decode(generated_ids["sequences"], skip_special_tokens=True, output_offsets=True)
+        self.assertEqual(transcript[0]["offsets"], EXPECTED_TRANSCRIPT)
+
     @slow
     def test_large_timestamp_generation(self):
         set_seed(0)