feat: add keyframe index extraction and frame/keyframe navigation

Wire ffprobe-based keyframe indexing through Tauri and auto-load positions after download completes.

Co-authored-by: Cursor <cursoragent@cursor.com>

src-tauri/src/commands/media_analysis.rs

@@ -1 +1,8 @@
-// Keyframe, waveform, thumbnail extraction commands — implemented in Tasks 9-11
+use crate::services::keyframe_index;
+
+#[tauri::command]
+pub async fn extract_keyframes(file_path: String) -> Result<Vec<f64>, String> {
+    tokio::task::spawn_blocking(move || keyframe_index::extract_keyframes(&file_path))
+        .await
+        .map_err(|e| format!("Task failed: {e}"))?
+}

src-tauri/src/lib.rs

@@ -2,7 +2,7 @@ mod commands;
 mod models;
 mod services;
 
-use commands::{dependencies, video};
+use commands::{dependencies, media_analysis, video};
 
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
@@ -16,6 +16,7 @@ pub fn run() {
             dependencies::install_dependency,
             video::resolve_url,
             video::start_download,
+            media_analysis::extract_keyframes,
         ])
         .run(tauri::generate_context!())
         .expect("error while running tauri application");

src-tauri/src/services/keyframe_index.rs

@@ -1 +1,70 @@
-// Implemented in Task 9
+use std::process::Command;
+
+pub fn parse_ffprobe_output(output: &str) -> Vec<f64> {
+    output
+        .lines()
+        .filter_map(|line| {
+            let parts: Vec<&str> = line.split(',').collect();
+            // Format: media_type,pts_time,flags
+            // We want lines where flags contain 'K' (keyframe)
+            if parts.len() >= 3 && parts[2].contains('K') {
+                parts[1].parse::<f64>().ok()
+            } else {
+                None
+            }
+        })
+        .collect()
+}
+
+pub fn extract_keyframes(file_path: &str) -> Result<Vec<f64>, String> {
+    let output = Command::new("ffprobe")
+        .args([
+            "-select_streams",
+            "v",
+            "-show_entries",
+            "frame=pts_time,flags",
+            "-of",
+            "csv=p=0",
+            "-skip_frame",
+            "nokey",
+            file_path,
+        ])
+        .output()
+        .map_err(|e| format!("Failed to run ffprobe: {e}"))?;
+
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        return Err(format!("ffprobe failed: {stderr}"));
+    }
+
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let mut positions = parse_ffprobe_output(&stdout);
+    positions.sort_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal));
+    Ok(positions)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_parse_ffprobe_keyframes() {
+        let output = "video,0.000000,K__\nvideo,0.500000,___\nvideo,1.000000,K__\nvideo,1.500000,___\nvideo,2.000000,K__\n";
+        let result = parse_ffprobe_output(output);
+        assert_eq!(result.len(), 3);
+        assert!((result[0] - 0.0).abs() < 0.001);
+        assert!((result[1] - 1.0).abs() < 0.001);
+        assert!((result[2] - 2.0).abs() < 0.001);
+    }
+
+    #[test]
+    fn test_parse_ffprobe_empty() {
+        assert!(parse_ffprobe_output("").is_empty());
+    }
+
+    #[test]
+    fn test_parse_ffprobe_no_keyframes() {
+        let output = "video,0.500000,___\nvideo,1.500000,___\n";
+        assert!(parse_ffprobe_output(output).is_empty());
+    }
+}

src/lib/bindings/mediaAnalysis.ts

@@ -1,3 +1,5 @@
+import { invoke } from '@tauri-apps/api/core';
+
 export interface ThumbnailSpritesheet {
   filePath: string;
   startIndex: number;
@@ -7,3 +9,7 @@ export interface ThumbnailSpritesheet {
   columns: number;
   intervalSeconds: number;
 }
+
+export async function extractKeyframes(filePath: string): Promise<number[]> {
+  return invoke<number[]>('extract_keyframes', { filePath });
+}

src/lib/stores/videoSession.svelte.ts

@@ -1,6 +1,7 @@
 import type { VideoMetadata } from '$lib/bindings/video';
 import { startDownload } from '$lib/bindings/video';
 import type { ThumbnailSpritesheet } from '$lib/bindings/mediaAnalysis';
+import { extractKeyframes } from '$lib/bindings/mediaAnalysis';
 
 export type SessionStatus = 'idle' | 'resolving' | 'ready' | 'error';
 export type DownloadStatus = 'idle' | 'downloading' | 'complete' | 'failed';
@@ -77,6 +78,15 @@ export function reset() {
   session.error = null;
 }
 
+async function triggerPostDownloadProcessing(filePath: string) {
+  try {
+    session.keyframePositions = await extractKeyframes(filePath);
+  } catch (e) {
+    console.error('Keyframe extraction failed:', e);
+  }
+  // Waveform and thumbnails will be added in Tasks 10 and 11
+}
+
 export async function beginDownload() {
   if (!session.url) return;
 
@@ -98,6 +108,7 @@ export async function beginDownload() {
           session.downloadProgress = 1.0;
           session.localFilePath = path;
           session.downloadStatus = 'complete';
+          void triggerPostDownloadProcessing(path);
         } else {
           session.downloadStatus = 'failed';
         }