[Docs] Add Stable Audio Open text-to-audio recipe

StabilityAI/Stable-Audio-Open.md

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+# Stable Audio Open Usage Guide
+
+This guide provides instructions for running Stable Audio Open text-to-audio generation using vLLM-Omni.
+
+## Supported Models
+
+- **stabilityai/stable-audio-open-1.0**: Text-to-Audio generation (44.1kHz, up to ~47s audio)
+
+## Installing vLLM-Omni
+
+```bash
+uv venv
+source .venv/bin/activate
+uv pip install vllm==0.14.1
+uv pip install git+https://github.com/vllm-project/vllm-omni.git
+```
+
+For audio file saving, install one of these packages:
+
+```bash
+uv pip install soundfile  # Recommended
+# or
+uv pip install scipy
+```
+
+The CLI examples below are from the vLLM-Omni repo. If you want to run them directly, clone that repo and run the scripts from its `examples/offline_inference` directory.
+
+## Text-to-Audio Generation
+
+### Basic Usage
+
+```python
+import torch
+import soundfile as sf
+from vllm_omni.entrypoints.omni import Omni
+
+omni = Omni(model="stabilityai/stable-audio-open-1.0")
+
+generator = torch.Generator(device="cuda").manual_seed(42)
+
+audio = omni.generate(
+    "The sound of a dog barking",
+    negative_prompt="Low quality.",
+    generator=generator,
+    guidance_scale=7.0,
+    num_inference_steps=100,
+    extra={
+        "audio_start_in_s": 0.0,
+        "audio_end_in_s": 10.0,
+    },
+)
+
+# Save audio output
+audio_data = audio[0].cpu().float().numpy().T  # [samples, channels]
+sf.write("output.wav", audio_data, 44100)
+```
+
+### CLI Usage
+
+```bash
+python examples/offline_inference/text_to_audio/text_to_audio.py \
+  --model stabilityai/stable-audio-open-1.0 \
+  --prompt "The sound of a dog barking" \
+  --audio_length 10.0 \
+  --num_inference_steps 100 \
+  --guidance_scale 7.0 \
+  --output dog_barking.wav
+```
+
+### More Examples
+
+```bash
+# Generate a piano melody
+python examples/offline_inference/text_to_audio/text_to_audio.py \
+  --prompt "A piano playing a gentle melody" \
+  --audio_length 15.0 \
+  --output piano_melody.wav
+
+# Generate ambient sounds with negative prompt
+python examples/offline_inference/text_to_audio/text_to_audio.py \
+  --prompt "Thunder and rain sounds" \
+  --negative_prompt "Low quality, distorted" \
+  --audio_length 20.0 \
+  --output thunder_rain.wav
+
+# Generate multiple waveforms
+python examples/offline_inference/text_to_audio/text_to_audio.py \
+  --prompt "A bird singing in the forest" \
+  --num_waveforms 3 \
+  --output bird_singing.wav
+```
+
+## Key Parameters
+
+| Parameter | Default | Description |
+|-----------|---------|-------------|
+| `audio_start_in_s` | 0.0 | Audio start time in seconds |
+| `audio_end_in_s` | 10.0 | Audio end time in seconds |
+| `audio_length` | 10.0 | Audio duration (CLI convenience, sets end time) |
+| `num_inference_steps` | 100 | Number of denoising steps |
+| `guidance_scale` | 7.0 | Classifier-free guidance scale |
+| `negative_prompt` | "Low quality." | Text describing unwanted audio characteristics |
+| `num_waveforms` | 1 | Number of audio samples to generate per prompt |
+| `sample_rate` | 44100 | Output sample rate in Hz |
+| `seed` | 42 | Random seed for reproducibility |
+
+## Notes
+
+- **Maximum audio length**: 47 seconds for stable-audio-open-1.0.
+- **Output format**: Stereo audio at 44.1kHz sample rate.
+- **Inference steps**: Higher `num_inference_steps` produces better quality but takes longer. The diffusers default is 200; vLLM-Omni example uses 100 for faster generation.
+- **Negative prompts**: Use to guide the model away from undesirable characteristics (e.g., "Low quality, distorted").
+- **Model size**: Approximately 1.2 billion parameters.
+
+## Limitations
+
+- **No realistic vocals**: The model cannot generate realistic singing or speech.
+- **English only**: Trained on English descriptions; performance degrades with other languages.
+- **Sound effects over music**: Better at generating sound effects than complex music.
+- **Prompt engineering**: May require experimentation with prompts for optimal results.
+
+## License
+
+Stable Audio Open is released under the [Stability AI Community License](https://huggingface.co/stabilityai/stable-audio-open-1.0/blob/main/LICENSE). Commercial use requires a separate license from Stability AI.
+
+## Additional Resources
+
+- [vLLM-Omni Text-to-Audio Example](https://github.com/vllm-project/vllm-omni/blob/main/examples/offline_inference/text_to_audio/text_to_audio.py)
+- [Stable Audio Open Model Card](https://huggingface.co/stabilityai/stable-audio-open-1.0)
+- [Stability AI](https://stability.ai/)