add text chunking for long-form generation (Fixes #4)

rust/README.md

@@ -2,6 +2,10 @@
 
 This guide provides examples for running TTS inference using Rust.
 
+## 📰 Update News
+
+**2025.11.19** - Added automatic text chunking for long-form inference. Long texts are split into chunks and synthesized with natural pauses.
+
 ## Installation
 
 This project uses [Cargo](https://doc.rust-lang.org/cargo/) for package management.
@@ -44,11 +48,13 @@ Process multiple voice styles and texts at once:
 ```bash
 # Using cargo run
 cargo run --release --bin example_onnx -- \
+  --batch \
   --voice-style assets/voice_styles/M1.json,assets/voice_styles/F1.json \
   --text "The sun sets behind the mountains, painting the sky in shades of pink and orange.|The weather is beautiful and sunny outside. A gentle breeze makes the air feel fresh and pleasant."
 
 # Or using the binary directly
 ./target/release/example_onnx \
+  --batch \
   --voice-style assets/voice_styles/M1.json,assets/voice_styles/F1.json \
   --text "The sun sets behind the mountains, painting the sky in shades of pink and orange.|The weather is beautiful and sunny outside. A gentle breeze makes the air feel fresh and pleasant."
 ```
@@ -79,6 +85,29 @@ This will:
 - Use 10 denoising steps instead of the default 5
 - Produce higher quality output at the cost of slower inference
 
+### Example 4: Long-Form Inference
+The system automatically chunks long texts into manageable segments, synthesizes each segment separately, and concatenates them with natural pauses (0.3 seconds by default) into a single audio file. This happens by default when you don't use the `--batch` flag:
+
+```bash
+# Using cargo run
+cargo run --release --bin example_onnx -- \
+  --voice-style assets/voice_styles/M1.json \
+  --text "This is a very long text that will be automatically split into multiple chunks. The system will process each chunk separately and then concatenate them together with natural pauses between segments. This ensures that even very long texts can be processed efficiently while maintaining natural speech flow and avoiding memory issues."
+
+# Or using the binary directly
+./target/release/example_onnx \
+  --voice-style assets/voice_styles/M1.json \
+  --text "This is a very long text that will be automatically split into multiple chunks. The system will process each chunk separately and then concatenate them together with natural pauses between segments. This ensures that even very long texts can be processed efficiently while maintaining natural speech flow and avoiding memory issues."
+```
+
+This will:
+- Automatically split the text into chunks based on paragraph and sentence boundaries
+- Synthesize each chunk separately
+- Add 0.3 seconds of silence between chunks for natural pauses
+- Concatenate all chunks into a single audio file
+
+**Note**: Automatic text chunking is disabled when using `--batch` mode. In batch mode, each text is processed as-is without chunking.
+
 ## Available Arguments
 
 | Argument | Type | Default | Description |
@@ -90,10 +119,12 @@ This will:
 | `--voice-style` | str+ | `assets/voice_styles/M1.json` | Voice style file path(s) |
 | `--text` | str+ | (long default text) | Text(s) to synthesize |
 | `--save-dir` | str | `results` | Output directory |
+| `--batch` | flag | False | Enable batch mode (multiple text-style pairs, disables automatic chunking) |
 
 ## Notes
 
-- **Batch Processing**: The number of `--voice-style` files must match the number of `--text` entries
+- **Batch Processing**: When using `--batch`, the number of `--voice-style` files must match the number of `--text` entries
+- **Automatic Chunking**: Without `--batch`, long texts are automatically split and concatenated with 0.3s pauses
 - **Quality vs Speed**: Higher `--total-step` values produce better quality but take longer
 - **GPU Support**: GPU mode is not supported yet
 - **Known Issues**: On some platforms (especially macOS), there might be a mutex cleanup warning during exit. This is a known ONNX Runtime issue and doesn't affect functionality. The implementation uses `libc::_exit()` and `mem::forget()` to bypass this issue.