Repository: huggingface/transformers
Pull request: Fix: align Qwen2.5-VL inference rope index with training by passing second_per_grid_ts

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## Bug

In Qwen2.5-VL, during inference the method `prepare_inputs_for_generation` calls `get_rope_index` without passing `second_per_grid_ts.`
However, during training, `second_per_grid_ts` is explicitly passed.

This leads to an inconsistency between training and inference:

Training: temporal positions are scaled according to `second_per_grid_ts`.

Inference: temporal positions fall back to the default (1.0), which may cause misalignment in temporal position encoding.

## Fix

Update `prepare_inputs_for_generation` to also pass `second_per_grid_ts` to `get_rope_index.`

## Impact

Ensures temporal position encoding consistency between training and inference.

Prevents potential misalignment in multi-frame or video-based inputs.

## Related Issue
Fixes #41152 


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Changed files:
filename: src/transformers/models/qwen2_5_vl/modeling_qwen2_5_vl.py
patch: @@ -1558,6 +1558,7 @@ def prepare_inputs_for_generation(
                     model_inputs.get("input_ids", None),
                     image_grid_thw=image_grid_thw,
                     video_grid_thw=video_grid_thw,
+                    second_per_grid_ts=second_per_grid_ts,
                     attention_mask=attention_mask,
                 )
                 self.model.rope_deltas = rope_deltas

filename: src/transformers/models/qwen2_5_vl/modular_qwen2_5_vl.py
patch: @@ -814,6 +814,7 @@ def prepare_inputs_for_generation(
                     model_inputs.get("input_ids", None),
                     image_grid_thw=image_grid_thw,
                     video_grid_thw=video_grid_thw,
+                    second_per_grid_ts=second_per_grid_ts,
                     attention_mask=attention_mask,
                 )
                 self.model.rope_deltas = rope_deltas