Make chapters accurate after cutting

src/sponskrub/ffwrap.d

@@ -71,14 +71,29 @@ ChapterTime[] get_chapter_times(string filename) {
 }
 import std.stdio;
 
-bool run_ffmpeg_filter(string input_filename, string output_filename, string filter, FileCategory category) {
+bool run_ffmpeg_filter(string input_filename, string output_filename, string filter, FileCategory category, string metadata = "") {
+	string metadata_filename = null;
+	scope(exit) {
+		if (metadata_filename !is null) {
+			remove(metadata_filename);
+		}
+	}
+
 	string[] args;
+	args = ["ffmpeg", "-loglevel", "warning", "-hide_banner", "-stats", "-i", input_filename];
+
+	if (metadata != "") {
+		metadata_filename = prepend_random_prefix(6, "-metadata.ffm");
+		write_metadata(metadata_filename, metadata);
+		args ~= ["-i", metadata_filename, "-map_metadata", "0", "-map_chapters", "1"];
+	}
+
 	if (category == FileCategory.AUDIO_VIDEO) {
-		args = ["ffmpeg", "-loglevel", "warning", "-hide_banner", "-stats", "-i", input_filename, "-filter_complex", filter, "-map", "[v]", "-map", "[a]",output_filename];
+		args ~= ["-filter_complex", filter, "-map", "[v]", "-map", "[a]", output_filename];
 	} else if (category == FileCategory.VIDEO) {
-		args = ["ffmpeg", "-loglevel", "warning", "-hide_banner", "-stats", "-i", input_filename, "-filter_complex", filter, "-map", "[v]", output_filename];
+		args ~= ["-filter_complex", filter, "-map", "[v]", output_filename];
 	}	else if (category == FileCategory.AUDIO) {
-		args = ["ffmpeg", "-loglevel", "warning", "-hide_banner", "-stats", "-i", input_filename, "-filter_complex", filter, "-map", "[a]", output_filename];
+		args ~= ["-filter_complex", filter, "-map", "[a]", output_filename];
 	}
 	auto ffmpeg_process = spawnProcess(args);
 	return wait(ffmpeg_process) == 0;

src/sponskrub/methods/chapter.d

@@ -115,10 +115,18 @@ ClipChapterTime[] merge_sponsor_times_with_chapters(ClipTime[] sponsor_times, Ch
 	return clip_chapters;
 }
 
+string generate_chapter_title(ClipChapterTime chapter) {
+	if (chapter.category == Categories.Content) {
+		return chapter.title;
+	} else {
+		return chapter.title~" <"~chapter.category~">";
+	}
+}
+
 string generate_chapters_metadata(ClipChapterTime[] chapter_times) {
 	return ";FFMETADATA1\n" ~
 		chapter_times.map!(
-			x => format_chapter_metadata(x.start, x.end, x.title~x.category)
+			chapter => format_chapter_metadata(chapter.start, chapter.end, generate_chapter_title(chapter))
 		).join("\n");
 }
 

src/sponskrub/methods/cut.d

@@ -27,16 +27,28 @@ import sponsorblock;
 import ffwrap;
 import chapter;
 
-ClipTime[] timestamps_to_keep(ClipChapterTime[] chapters) {
-	//we can redo this so it just filters a bunch of chapter times and includes only content
+ClipChapterTime[] timestamps_to_keep(ClipChapterTime[] chapters) {
 	return chapters
 		.sort!((a, b) => a.start.to!float < b.start.to!float)
 		.filter!(chapter => chapter.category == Categories.Content)
-		.map!(chapter => ClipTime(chapter.start, chapter.end, "")) //we need better types, this shouldn't need a category
 		.array;
 }
 
-string cut_and_cat_clips_filter(ClipTime[] timestamps, FileCategory category) {
+ClipChapterTime[] calculate_timestamps_for_kept_clips(ClipChapterTime[] chapters) {
+	auto current_time = "0";
+	ClipChapterTime[] adjusted_chapters = [];
+
+	foreach (ClipChapterTime chapter; chapters) {
+		auto duration = chapter.end.to!float - chapter.start.to!float;
+		auto end_time = (current_time.to!float + duration).to!string; // I really need to deal with this bouncing between strings and floats nonsense
+		adjusted_chapters ~= ClipChapterTime(current_time, end_time, chapter.category, chapter.title);
+		current_time = end_time;
+	}
+	return adjusted_chapters;
+
+}
+
+string cut_and_cat_clips_filter(ClipChapterTime[] timestamps, FileCategory category) {
   timestamps.sort!((a, b) => a.start.to!float < b.start.to!float);
 
 	auto clip_indexes = iota(0, timestamps.length);

src/sponskrub/sponskrub.d

@@ -145,8 +145,8 @@ Options:
 			ClipChapterTime[] new_chapter_times;
 
 			chapter_times = get_chapter_times(input_filename);
-
-			if (chapter_times.length == 0) {
+			auto input_chapters_count = chapter_times.length;
+			if (input_chapters_count == 0) {
 				chapter_times = [ChapterTime("0", video_length, "sponskrub-content")];
 			}
 
@@ -161,16 +161,15 @@ Options:
 					generate_chapters_metadata(new_chapter_times)
 				);
 			} else {
-				//using the chapter data also means that in future we could also adjust
-				//preexisting chapter metadata to remain accurate after the cut
 				writeln("Surgically removing the shilling...");
 				auto content_times = timestamps_to_keep(new_chapter_times);
 
 				ffmpeg_status = run_ffmpeg_filter(
 					input_filename,
 					output_filename,
 					cut_and_cat_clips_filter(content_times, get_file_category(input_filename)),
-					get_file_category(input_filename)
+					get_file_category(input_filename),
+					generate_chapters_metadata(calculate_timestamps_for_kept_clips(content_times))
 				);
 			}