Add chapter metadata - added m4b format, generating chapters info and converting via ffmpeg

abogen/conversion.py

@@ -10,7 +10,7 @@ import soundfile as sf
 from utils import clean_text
 from constants import PROGRAM_NAME, LANGUAGE_DESCRIPTIONS, SAMPLE_VOICE_TEXTS
 from voice_formulas import get_new_voice
-
+import static_ffmpeg
 
 def get_sample_voice_text(lang_code):
     return SAMPLE_VOICE_TEXTS.get(lang_code, SAMPLE_VOICE_TEXTS["a"])
@@ -334,6 +334,12 @@ class ConversionThread(QThread):
             # Initialize current segment counter
             current_segment = 0
 
+            # Initialize chapter times
+            chapters_time = [
+                {"chapter": chapter[0], "start": 0.0, "end": 0.0}
+                for chapter in chapters
+            ]
+
             # Instead of processing the whole text, process by chapter
             for chapter_idx, (chapter_name, chapter_text) in enumerate(chapters, 1):
                 if total_chapters > 1:
@@ -349,6 +355,10 @@ class ConversionThread(QThread):
                 chapter_subtitle_entries = []
                 chapter_current_time = 0.0
 
+                # chapter start time
+                chapter_time = chapters_time[chapter_idx - 1]
+                chapter_time["start"] = current_time
+
                 # Set split_pattern to \n+ which will split on one or more newlines
                 split_pattern = r"\n+"
                 
@@ -462,6 +472,9 @@ class ConversionThread(QThread):
                     # Update progress more frequently (after each result)
                     self.progress_updated.emit(percent, etr_str)
 
+                # Update chapter end time
+                chapter_time["end"] = current_time
+
                 # Save the individual chapter output if save_chapters_separately is enabled
                 if (
                     save_chapters_separately
@@ -532,7 +545,17 @@ class ConversionThread(QThread):
                 out_filename = f"{base_name}{suffix}.{self.output_format}"
                 out_path = os.path.join(out_dir, out_filename)
                 srt_path = os.path.splitext(out_path)[0] + ".srt"
+
+                # in case the user picked m4b format, we need to change the output format to wav
+                if self.output_format == "m4b":
+                    picked_out_path = out_path
+                    out_path = os.path.splitext(out_path)[0] + ".wav"
+                    self.output_format = "wav"
+                    m4b_picked = True
                 sf.write(out_path, audio, 24000, format=self.output_format)
+                if m4b_picked:
+                    out_path = self._generate_m4b_with_chapters(out_path, chapters_time)
+
                 if self.subtitle_mode != "Disabled":
                     with open(srt_path, "w", encoding="utf-8", errors="replace") as srt_file:
                         for i, (start, end, text) in enumerate(subtitle_entries, 1):
@@ -571,6 +594,46 @@ class ConversionThread(QThread):
         self.merge_chapters_at_end = options["merge_chapters_at_end"]
         self.waiting_for_user_input = False
 
+    def _generate_m4b_with_chapters(self, out_path, chapters_time):
+        # generate chapters.txt in the same folder as the output file
+        chapters_info_path = os.path.splitext(out_path)[0] + "_chapters.txt"
+        with open(chapters_info_path, "w", encoding="utf-8") as f:
+            f.write(';FFMETADATA1\n') # required header for ffmpeg
+            for chapter in chapters_time:
+                f.write(f"[CHAPTER]\n")
+                f.write(f"TIMEBASE=1/10\n")
+                # use 10th of second for start/end time
+                f.write(f"START={int(chapter["start"]*10)}\n")
+                f.write(f"END={int(chapter["end"]*10)}\n")
+                f.write(f"title={chapter["chapter"]}\n\n")
+        # call ffmpeg to merge the chapters into the output file
+        # ffmpeg installed on first call to add_paths()
+        static_ffmpeg.add_paths()
+        import subprocess
+        out_path_m4b = os.path.splitext(out_path)[0] + ".m4b"
+        # ffmpeg -i input.m4b -i ch.txt -map 0:a -map_chapters 1 output.m4b
+        ffmpeg_cmd = [
+            "ffmpeg",
+            "-i", out_path,
+            "-i", chapters_info_path,
+            "-map", "0:a",
+            "-map_chapters", "1",
+            out_path_m4b
+        ]
+        try:
+            result = subprocess.run(ffmpeg_cmd, capture_output=True, text=True)
+            # TODO Check for errors in the ffmpeg command
+        except subprocess.CalledProcessError as e:
+            self.log_updated.emit(
+                (f"FFmpeg error: {e.stderr}", "red")
+            )
+            return out_path
+        # delete the chapters path and original (wav) file
+        os.remove(chapters_info_path)
+        os.remove(out_path)
+        # the new file is in m4b format - use that for messages
+        return out_path_m4b
+
     def _srt_time(self, t):
         """Helper function to format time for SRT files"""
         h = int(t // 3600)

abogen/gui.py

@@ -652,7 +652,7 @@ class abogen(QWidget):
         self.format_combo.setStyleSheet(
             "QComboBox { min-height: 20px; padding: 6px 12px; }"
         )
-        format_options = ["wav", "flac", "mp3"]
+        format_options = ["wav", "flac", "mp3", "m4b"]
         self.format_combo.addItems(format_options)
         self.format_combo.setCurrentText(self.selected_format)
         self.format_combo.currentTextChanged.connect(self.on_format_changed)

pyproject.toml

@@ -21,7 +21,8 @@ dependencies = [
     "soundfile>=0.13.1",
     "pygame>=2.6.1",
     "charset_normalizer>=3.4.1",
-    "chardet>=5.2.0"
+    "chardet>=5.2.0",
+    "static_ffmpeg>=2.13"
 ]
 
 classifiers = [