Support per-video use_audio_in_video for Qwen Omni

[hbhflw2000]

Summary

This PR adds per-video use_audio_in_video support for Qwen Omni models.

Previously, use_audio_in_video was treated as a global boolean. This made mixed video prompts hard to handle when some videos contain audio and others do not. In that case, vLLM could extract audio and update placeholders as if every video had audio, which could cause video/audio placeholder mismatches.

With this PR, mm_processor_kwargs["use_audio_in_video"] can be either:

• a boolean, preserving the existing global behavior
• a list of booleans, one value per video

For example:

mm_processor_kwargs={"use_audio_in_video": [True, False]}

This means the first video is processed with audio-in-video enabled, while the second video is processed as a video-only item.

Changes

• Track parsed video indices in sync and async chat multimodal parsers.
• Extract audio from video only for video items whose corresponding mask value is True.
• Normalize use_audio_in_video in Qwen2.5 Omni and Qwen3 Omni processors.
• Store per-video audio-in-video flags as batched multimodal fields.
• Update prompt replacement logic to interleave audio placeholders only for videos whose mask is enabled.
• Fix explicit False handling so it is not treated as a missing value.
• Add a mixed-mask regression test.

Compatibility

Existing boolean usage is preserved:

mm_processor_kwargs={"use_audio_in_video": True}
mm_processor_kwargs={"use_audio_in_video": False}

The new list form only changes behavior when users explicitly pass per-video values.

Validation

Ran the following checks on the upstream main checkout:

python -m ruff check \
  vllm/entrypoints/chat_utils.py \
  vllm/model_executor/models/qwen2_5_omni_thinker.py \
  vllm/model_executor/models/qwen3_omni_moe_thinker.py \
  tests/models/multimodal/processing/test_audio_in_video.py

python -m ruff format --check \
  vllm/entrypoints/chat_utils.py \
  vllm/model_executor/models/qwen2_5_omni_thinker.py \
  vllm/model_executor/models/qwen3_omni_moe_thinker.py \
  tests/models/multimodal/processing/test_audio_in_video.py

git diff --check

python -m pytest -q \
  tests/models/multimodal/processing/test_audio_in_video.py \
  -k per_video_mask_mixed

Result:

2 passed, 4 deselected

I also validated the same change on a vLLM 0.20.2 environment with full Qwen3-Omni-30B-A3B-Instruct using two videos:

• Video 1: video with audio
• Video 2: video without audio

The request used:

mm_processor_kwargs={"use_audio_in_video": [True, False]}

The full-model TP4 generation completed successfully.

[github-actions]

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[hbhflw2000]

moved to vllm-omni vllm-project/vllm-omni#4656