Add maximum chapter duration cap when splitting by chapter (#1680)

Source/FileLiberator/DownloadOptions.Factory.cs

@@ -194,7 +194,11 @@ var chapters
 			stripBranding(chapters, licInfo.ContentMetadata.ChapterInfo.BrandIntroDurationMs, licInfo.ContentMetadata.ChapterInfo.BrandOutroDurationMs);
 
 		if (config.SplitFilesByChapter)
+		{
 			combineShortChapters(chapters, config.MinimumFileDuration * 1000);
+			if (config.MaximumFileDuration > 0)
+				splitLongChapters(chapters, config.MaximumFileDuration * 1000);
+		}
 
 		var dlOptions = new DownloadOptions(config, libraryBook, licInfo)
 		{
@@ -390,6 +394,39 @@ public static void combineShortChapters(List<Chapter> chapters, long minChapterL
 		}
 	}
 
+	public static void splitLongChapters(List<Chapter> chapters, long maxChapterLengthMs)
+	{
+		for (int i = 0; i < chapters.Count; i++)
+		{
+			if (chapters[i].LengthMs <= maxChapterLengthMs)
+				continue;
+
+			var original = chapters[i];
+			int totalParts = (int)Math.Ceiling((double)original.LengthMs / maxChapterLengthMs);
+			var parts = new List<Chapter>(totalParts);
+			long offset = original.StartOffsetMs;
+			long remaining = original.LengthMs;
+
+			for (int part = 1; part <= totalParts; part++)
+			{
+				long partLength = Math.Min(remaining, maxChapterLengthMs);
+				parts.Add(new Chapter
+				{
+					Title = $"{original.Title} (Part {part} of {totalParts})",
+					StartOffsetMs = offset,
+					StartOffsetSec = offset / 1000,
+					LengthMs = partLength,
+				});
+				offset += partLength;
+				remaining -= partLength;
+			}
+
+			chapters.RemoveAt(i);
+			chapters.InsertRange(i, parts);
+			i += parts.Count - 1;
+		}
+	}
+
 	public static void stripBranding(List<Chapter> chapters, long introMs, long outroMs)
 	{
 		chapters[0].LengthMs -= introMs;

Source/LibationAvalonia/Controls/Settings/Audio.axaml

@@ -154,14 +154,14 @@
 					<Grid
 						Margin="0,0,0,5"
 						Grid.ColumnDefinitions="Auto,Auto"
-						Grid.RowDefinitions="Auto,Auto">
-						
-						<CheckBox Margin="0" Grid.ColumnSpan="2" IsChecked="{Binding SplitFilesByChapter, Mode=TwoWay}">						
-							<TextBlock Grid.ColumnSpan="2" Text="{Binding SplitFilesByChapterText}" />						
+						Grid.RowDefinitions="Auto,Auto,Auto">
+
+						<CheckBox Margin="0" Grid.ColumnSpan="2" IsChecked="{Binding SplitFilesByChapter, Mode=TwoWay}">
+							<TextBlock Grid.ColumnSpan="2" Text="{Binding SplitFilesByChapterText}" />
 						</CheckBox>
 
 						<TextBlock Grid.Row="1" Margin="15,0" VerticalAlignment="Center" ToolTip.Tip="{Binding MinimumFileDurationTip}" Text="{Binding MinimumFileDurationText}" />
-							
+
 						<NumericUpDown
 							Classes="SmallNumericUpDown"
 							Grid.Column="1"
@@ -175,6 +175,22 @@
 							ParsingNumberStyle="Integer"
 							IsEnabled="{Binding SplitFilesByChapter}"
 							Value="{Binding MinimumFileDuration, Mode=TwoWay}"/>
+
+						<TextBlock Grid.Row="2" Margin="15,0" VerticalAlignment="Center" ToolTip.Tip="{Binding MaximumFileDurationTip}" Text="{Binding MaximumFileDurationText}" />
+
+						<NumericUpDown
+							Classes="SmallNumericUpDown"
+							Grid.Column="1"
+							Grid.Row="2"
+							ToolTip.Tip="{Binding MaximumFileDurationTip}"
+							MinWidth="100"
+							Minimum="0"
+							Maximum="1440"
+							Increment="1"
+							FormatString="N0"
+							ParsingNumberStyle="Integer"
+							IsEnabled="{Binding SplitFilesByChapter}"
+							Value="{Binding MaximumFileDuration, Mode=TwoWay}"/>
 					</Grid>
 
 					<CheckBox

Source/LibationAvalonia/ViewModels/Settings/AudioSettingsVM.cs

@@ -40,6 +40,7 @@ public AudioSettingsVM(Configuration config)
 		ClipBookmarkFormat = config.ClipsBookmarksFileFormat;
 		SplitFilesByChapter = config.SplitFilesByChapter;
 		MinimumFileDuration = config.MinimumFileDuration;
+		MaximumFileDuration = config.MaximumFileDuration;
 		MergeOpeningAndEndCredits = config.MergeOpeningAndEndCredits;
 		StripAudibleBrandAudio = config.StripAudibleBrandAudio;
 		StripUnabridged = config.StripUnabridged;
@@ -73,6 +74,7 @@ public void SaveSettings(Configuration config)
 		config.ClipsBookmarksFileFormat = ClipBookmarkFormat;
 		config.SplitFilesByChapter = SplitFilesByChapter;
 		config.MinimumFileDuration = MinimumFileDuration;
+		config.MaximumFileDuration = MaximumFileDuration;
 		config.MergeOpeningAndEndCredits = MergeOpeningAndEndCredits;
 		config.StripAudibleBrandAudio = StripAudibleBrandAudio;
 		config.StripUnabridged = StripUnabridged;
@@ -121,6 +123,7 @@ public void SaveSettings(Configuration config)
 	public string RetainAaxFileText { get; } = Configuration.GetDescription(nameof(Configuration.RetainAaxFile));
 	public string SplitFilesByChapterText { get; } = Configuration.GetDescription(nameof(Configuration.SplitFilesByChapter));
 	public string MinimumFileDurationText { get; } = Configuration.GetDescription(nameof(Configuration.MinimumFileDuration));
+	public string MaximumFileDurationText { get; } = Configuration.GetDescription(nameof(Configuration.MaximumFileDuration));
 	public string MergeOpeningEndCreditsText { get; } = Configuration.GetDescription(nameof(Configuration.MergeOpeningAndEndCredits));
 	public string StripAudibleBrandingText { get; } = Configuration.GetDescription(nameof(Configuration.StripAudibleBrandAudio));
 	public string StripUnabridgedText { get; } = Configuration.GetDescription(nameof(Configuration.StripUnabridged));
@@ -150,6 +153,7 @@ public void SaveSettings(Configuration config)
 	public bool DecryptToLossy { get => field; set => this.RaiseAndSetIfChanged(ref field, value); }
 	public string DecryptToLossyTip => Configuration.GetHelpText(nameof(DecryptToLossy));
 	public string MinimumFileDurationTip => Configuration.GetHelpText(nameof(MinimumFileDuration));
+	public string MaximumFileDurationTip => Configuration.GetHelpText(nameof(MaximumFileDuration));
 	public bool MoveMoovToBeginning { get; set; }
 
 	public bool LameDownsampleMono { get; set; } = Design.IsDesignMode;
@@ -158,6 +162,7 @@ public void SaveSettings(Configuration config)
 
 	public bool SplitFilesByChapter { get => field; set { this.RaiseAndSetIfChanged(ref field, value); } }
 	public int MinimumFileDuration { get => field; set { this.RaiseAndSetIfChanged(ref field, value); } }
+	public int MaximumFileDuration { get => field; set { this.RaiseAndSetIfChanged(ref field, value); } }
 	public bool LameTargetBitrate { get => field; set { this.RaiseAndSetIfChanged(ref field, value); } }
 	public bool LameMatchSource { get => field; set { this.RaiseAndSetIfChanged(ref field, value); } }
 	public int LameBitrate { get => field; set { this.RaiseAndSetIfChanged(ref field, value); } }

Source/LibationFileManager/Configuration.HelpText.cs

@@ -88,6 +88,13 @@ this duration will be merged with the following
 			chapter. Merged chapter titles will be joined with
 			a space between them.
 			""" },
+		{nameof(MaximumFileDuration), """
+			The maximum duration (in minutes) for a chapter to
+			be split into its own file. Chapters longer than
+			this duration will be divided into equal-length
+			parts. Part titles are suffixed with "(Part N of M)".
+			Set to 0 to disable.
+			""" },
 		{nameof(SpatialAudioCodec), """
 			The Dolby Digital Plus (E-AC-3) codec is more widely
 			supported than the AC-4 codec, but E-AC-3 files are

Source/LibationFileManager/Configuration.PersistentSettings.cs

@@ -173,6 +173,9 @@ public string InProgress
 	[Description("Minimum file duration (seconds)")]
 	public int MinimumFileDuration { get => Math.Max(0, GetNonString(defaultValue: 3)); set => SetNonString(value); }
 
+	[Description("Maximum file duration (seconds)")]
+	public int MaximumFileDuration { get => Math.Max(0, GetNonString(defaultValue: 0)); set => SetNonString(value); }
+
 	[Description("Merge Opening/End Credits into the following/preceding chapters")]
 	public bool MergeOpeningAndEndCredits { get => GetNonString(defaultValue: false); set => SetNonString(value); }
 

Source/LibationWinForms/Dialogs/SettingsDialog.AudioSettings.cs

@@ -20,6 +20,7 @@ private void Load_AudioSettings(Configuration config)
 		this.combineNestedChapterTitlesCbox.Text = desc(nameof(config.CombineNestedChapterTitles));
 		this.splitFilesByChapterCbox.Text = desc(nameof(config.SplitFilesByChapter));
 		this.minFileDurationLbl.Text = desc(nameof(config.MinimumFileDuration));
+		this.maxFileDurationLbl.Text = desc(nameof(config.MaximumFileDuration));
 		this.mergeOpeningEndCreditsCbox.Text = desc(nameof(config.MergeOpeningAndEndCredits));
 		this.stripAudibleBrandingCbox.Text = desc(nameof(config.StripAudibleBrandAudio));
 		this.stripUnabridgedCbox.Text = desc(nameof(config.StripUnabridged));
@@ -80,6 +81,7 @@ private void Load_AudioSettings(Configuration config)
 		combineNestedChapterTitlesCbox.Checked = config.CombineNestedChapterTitles;
 		splitFilesByChapterCbox.Checked = config.SplitFilesByChapter;
 		minFileDurationNud.Value = config.MinimumFileDuration;
+		maxFileDurationNud.Value = config.MaximumFileDuration;
 		mergeOpeningEndCreditsCbox.Checked = config.MergeOpeningAndEndCredits;
 		stripUnabridgedCbox.Checked = config.StripUnabridged;
 		stripAudibleBrandingCbox.Checked = config.StripAudibleBrandAudio;
@@ -124,6 +126,7 @@ private void Save_AudioSettings(Configuration config)
 		config.CombineNestedChapterTitles = combineNestedChapterTitlesCbox.Checked;
 		config.SplitFilesByChapter = splitFilesByChapterCbox.Checked;
 		config.MinimumFileDuration = (int)minFileDurationNud.Value;
+		config.MaximumFileDuration = (int)maxFileDurationNud.Value;
 		config.MergeOpeningAndEndCredits = mergeOpeningEndCreditsCbox.Checked;
 		config.StripUnabridged = stripUnabridgedCbox.Checked;
 		config.StripAudibleBrandAudio = stripAudibleBrandingCbox.Checked;
@@ -159,7 +162,7 @@ private void LameMatchSourceBRCbox_CheckedChanged(object sender, EventArgs e)
 
 	private void splitFilesByChapterCbox_CheckedChanged(object sender, EventArgs e)
 	{
-		chapterTitleTemplateGb.Enabled = minFileDurationNud.Enabled = minFileDurationLbl.Enabled = splitFilesByChapterCbox.Checked;
+		chapterTitleTemplateGb.Enabled = minFileDurationNud.Enabled = minFileDurationLbl.Enabled = maxFileDurationNud.Enabled = maxFileDurationLbl.Enabled = splitFilesByChapterCbox.Checked;
 	}
 
 	private void chapterTitleTemplateBtn_Click(object sender, EventArgs e)

Source/_Tests/FileLiberator.Tests/DownloadDecryptBookTests.cs

@@ -538,4 +538,116 @@ private static void checkChapters(IList<Chapter> value, IList<Chapter> expected)
 			value[i].LengthMs.Should().Be(expected[i].LengthMs);
 		}
 	}
+
+	[TestMethod]
+	public void SplitLongChapters_ShortChapter_NotSplit()
+	{
+		var chapters = new List<Chapter>
+		{
+			new() { Title = "Chapter 1", StartOffsetMs = 0, StartOffsetSec = 0, LengthMs = 60_000 },
+		};
+
+		DownloadOptions.splitLongChapters(chapters, 120_000);
+
+		chapters.Count.Should().Be(1);
+		chapters[0].Title.Should().Be("Chapter 1");
+		chapters[0].LengthMs.Should().Be(60_000);
+	}
+
+	[TestMethod]
+	public void SplitLongChapters_ExactlyAtLimit_NotSplit()
+	{
+		var chapters = new List<Chapter>
+		{
+			new() { Title = "Chapter 1", StartOffsetMs = 0, StartOffsetSec = 0, LengthMs = 120_000 },
+		};
+
+		DownloadOptions.splitLongChapters(chapters, 120_000);
+
+		chapters.Count.Should().Be(1);
+		chapters[0].Title.Should().Be("Chapter 1");
+	}
+
+	[TestMethod]
+	public void SplitLongChapters_TwoParts_SplitsEvenly()
+	{
+		var chapters = new List<Chapter>
+		{
+			new() { Title = "Chapter 1", StartOffsetMs = 0, StartOffsetSec = 0, LengthMs = 200_000 },
+		};
+
+		DownloadOptions.splitLongChapters(chapters, 100_000);
+
+		chapters.Count.Should().Be(2);
+		chapters[0].Title.Should().Be("Chapter 1 (Part 1 of 2)");
+		chapters[0].StartOffsetMs.Should().Be(0);
+		chapters[0].StartOffsetSec.Should().Be(0);
+		chapters[0].LengthMs.Should().Be(100_000);
+		chapters[1].Title.Should().Be("Chapter 1 (Part 2 of 2)");
+		chapters[1].StartOffsetMs.Should().Be(100_000);
+		chapters[1].StartOffsetSec.Should().Be(100);
+		chapters[1].LengthMs.Should().Be(100_000);
+	}
+
+	[TestMethod]
+	public void SplitLongChapters_ThreeParts_LastPartShorter()
+	{
+		var chapters = new List<Chapter>
+		{
+			new() { Title = "Long Chapter", StartOffsetMs = 0, StartOffsetSec = 0, LengthMs = 250_000 },
+		};
+
+		DownloadOptions.splitLongChapters(chapters, 100_000);
+
+		chapters.Count.Should().Be(3);
+		chapters[0].LengthMs.Should().Be(100_000);
+		chapters[1].LengthMs.Should().Be(100_000);
+		chapters[2].LengthMs.Should().Be(50_000);
+		chapters[2].StartOffsetMs.Should().Be(200_000);
+		chapters[2].StartOffsetSec.Should().Be(200);
+		chapters[2].Title.Should().Be("Long Chapter (Part 3 of 3)");
+	}
+
+	[TestMethod]
+	public void SplitLongChapters_OffsetPreserved()
+	{
+		var chapters = new List<Chapter>
+		{
+			new() { Title = "Chapter 1", StartOffsetMs = 0, StartOffsetSec = 0, LengthMs = 60_000 },
+			new() { Title = "Chapter 2", StartOffsetMs = 60_000, StartOffsetSec = 60, LengthMs = 200_000 },
+		};
+
+		DownloadOptions.splitLongChapters(chapters, 100_000);
+
+		chapters.Count.Should().Be(3);
+		chapters[0].Title.Should().Be("Chapter 1");
+		chapters[1].Title.Should().Be("Chapter 2 (Part 1 of 2)");
+		chapters[1].StartOffsetMs.Should().Be(60_000);
+		chapters[1].StartOffsetSec.Should().Be(60);
+		chapters[1].LengthMs.Should().Be(100_000);
+		chapters[2].Title.Should().Be("Chapter 2 (Part 2 of 2)");
+		chapters[2].StartOffsetMs.Should().Be(160_000);
+		chapters[2].StartOffsetSec.Should().Be(160);
+		chapters[2].LengthMs.Should().Be(100_000);
+	}
+
+	[TestMethod]
+	public void SplitLongChapters_MultipleChaptersOnlyLongOnesSplit()
+	{
+		var chapters = new List<Chapter>
+		{
+			new() { Title = "Short", StartOffsetMs = 0, StartOffsetSec = 0, LengthMs = 30_000 },
+			new() { Title = "Long", StartOffsetMs = 30_000, StartOffsetSec = 30, LengthMs = 300_000 },
+			new() { Title = "Short2", StartOffsetMs = 330_000, StartOffsetSec = 330, LengthMs = 30_000 },
+		};
+
+		DownloadOptions.splitLongChapters(chapters, 100_000);
+
+		chapters.Count.Should().Be(5);
+		chapters[0].Title.Should().Be("Short");
+		chapters[1].Title.Should().Be("Long (Part 1 of 3)");
+		chapters[2].Title.Should().Be("Long (Part 2 of 3)");
+		chapters[3].Title.Should().Be("Long (Part 3 of 3)");
+		chapters[4].Title.Should().Be("Short2");
+	}
 }