Refactor and add scheduled task

src/Jellyfin.MediaEncoding.Hls/Extractors/IKeyframeExtractor.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using Jellyfin.MediaEncoding.Keyframes;
+
+namespace Jellyfin.MediaEncoding.Hls.Extractors;
+
+/// <summary>
+/// Keyframe extractor.
+/// </summary>
+public interface IKeyframeExtractor
+{
+    /// <summary>
+    /// Gets a value indicating whether the extractor is based on container metadata.
+    /// </summary>
+    bool IsMetadataBased { get; }
+
+    /// <summary>
+    /// Attempt to extract keyframes.
+    /// </summary>
+    /// <param name="filePath">The path to the file.</param>
+    /// <param name="keyframeData">The keyframes.</param>
+    /// <returns>A value indicating whether the keyframe extraction was successful.</returns>
+    bool TryExtractKeyframes(string filePath, [NotNullWhen(true)] out KeyframeData? keyframeData);
+}