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+# API Documentation
+
+This document provides API documentation for using video_probe as a library.
+
+## Installation
+
+Add to your Cargo.toml:
+
+```toml
+[dependencies]
+video_probe = { path = "../video_probe" }
+```
+
+## Quick Start
+
+```rust
+use video_probe::*;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // Probe video
+    let metadata = probe_video("video.mp4")?;
+    
+    // Access metadata
+    println!("Duration: {} seconds", metadata.format.duration);
+    
+    if let Some(ref video) = metadata.video_stream {
+        println!("Resolution: {}x{}", video.width, video.height);
+    }
+    
+    // Save to file
+    let output_file = save_metadata("video.mp4", &metadata)?;
+    println!("Saved to: {}", output_file);
+    
+    Ok(())
+}
+```
+
+## Core Functions
+
+### probe_video
+
+```rust
+pub fn probe_video(video_path: &str) -> Result<VideoMetadata>
+```
+
+Probes a video file and returns metadata.
+
+### probe_video_to_file
+
+```rust
+pub fn probe_video_to_file(video_path: &str) -> Result<String>
+```
+
+Probes a video and saves metadata to JSON file.
+
+### save_metadata
+
+```rust
+pub fn save_metadata(video_path: &str, metadata: &VideoMetadata) -> Result<String>
+```
+
+Saves metadata to a JSON file.
+
+### print_summary
+
+```rust
+pub fn print_summary(metadata: &VideoMetadata)
+```
+
+Prints formatted summary to console.
+
+## Data Structures
+
+### VideoMetadata
+
+- `video_path`: String
+- `probed_at`: DateTime<Utc>
+- `format`: FormatInfo
+- `video_stream`: Option<VideoStream>
+- `audio_streams`: Vec<AudioStream>
+- `subtitle_streams`: Vec<SubtitleStream>