FF-371 - FFmpeg builder now automatically converting subtitles if container changes

VideoNodes/Helpers/SubtitleHelper.cs

@@ -1,21 +1,83 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace FileFlows.VideoNodes.Helpers;
+namespace FileFlows.VideoNodes.Helpers;
 
 /// <summary>
 /// Helper for Subtitles
 /// </summary>
 internal class SubtitleHelper
 {
+    
+    public static readonly string[]  MkvSubtitles = new[]
+    {
+        "ass",        // Advanced SubStation Alpha
+        "ssa",        // SubStation Alpha subtitle
+        "srt",        // SubRip subtitle
+        "subrip",     // SubRip subtitle (alternative name)
+        "vtt",        // WebVTT subtitle
+        "webvtt",     // WebVTT subtitle (alternative name)
+        "smi",        // SAMI subtitle format
+        "sami",       // SAMI subtitle format (alternative name)
+        "rt",         // RealText subtitle format
+        "realtext",   // RealText subtitle format (alternative name)
+        "stl",        // EBU STL (Subtitling Data Exchange Format)
+        "ttml",       // Timed Text Markup Language
+        "ttml_legacy" // Timed Text Markup Language (legacy name)
+    };
+    
     /// <summary>
     /// Tests if a subtitle is an image based subtitle
     /// </summary>
     /// <param name="codec">the subtitle codec</param>
     /// <returns>true if the subtitle is an image based subtitle</returns>
     internal static bool IsImageSubtitle(string codec)
-        => Regex.IsMatch(codec.Replace("_", ""), "dvbsub|dvdsub|pgs|xsub", RegexOptions.IgnoreCase);
+        => Regex.IsMatch(codec.Replace("_", ""), "dvbsub|pgs|xsub|vobsub", RegexOptions.IgnoreCase);
+
+    /// <summary>
+    /// Determines the appropriate subtitle codec for conversion based on the container type and current subtitle codec.
+    /// </summary>
+    /// <param name="containerType">The container type (mp4, mkv, webm).</param>
+    /// <param name="currentCodec">The current subtitle codec.</param>
+    /// <returns>The appropriate subtitle codec for conversion, or null container does not support this codec.</returns>
+    public static string? GetSubtitleCodec(string containerType, string currentCodec)
+    {
+        // Check if the current subtitle codec is image-based
+        bool isImageBased = IsImageSubtitle(currentCodec);
+
+        // Determine the appropriate subtitle codec based on the container type and if the current codec is image-based or text-based
+        switch (containerType.ToLower())
+        {
+            case "mp4":
+                if (isImageBased)
+                {
+                    // MP4 container does not support image-based subtitles, so conversion is not possible
+                    return null;
+                }
+                return "mov_text";
+            case "mkv":
+                if (isImageBased)
+                    return "hdmv_pgs_subtitle";
+                if (IsSupportedSubtitleCodecMKV(currentCodec) == false)
+                    return "srt"; // or "ssa" or any other supported codec
+                return currentCodec;
+            case "webm":
+                if (isImageBased)
+                {
+                    // WebM container does not support image-based subtitles, so conversion is not possible
+                    return null;
+                }
+                // WebM container supports text-based subtitles in the webvtt codec
+                return "webvtt";
+            default:
+                // Invalid or unsupported container type
+                return null;
+        }
+    }
+    
+    /// <summary>
+    /// Checks if the subtitle codec is supported in MKV container.
+    /// </summary>
+    /// <param name="codec">The subtitle codec to check.</param>
+    /// <returns>True if the codec is supported in MKV, False otherwise.</returns>
+    private static bool IsSupportedSubtitleCodecMKV(string codec)
+        => Array.IndexOf(MkvSubtitles, codec.ToLower()) >= 0;
+
 }