Add bitrate option

Author: Tsubashi

src/m4b_util/helpers/audiobook.py

@@ -22,8 +22,7 @@
 class Audiobook:
     """Store all the info pertaining to an audiobook."""
     author: str = None
-    # Set duration to a big number, (hopefully larger than our actual duration)
-    # just in case we try to write chapters without knowing the final duration.
+    bitrate: str = "128k"
     chapters: list = field(default_factory=lambda: [])
     cover: str = None
     date: str = None
@@ -284,7 +283,7 @@ def _bind_multiple_segments(self, output_path):
             if segment.title:
                 cmd.extend(["-metadata", f"title={segment.title}"])
             cmd.extend(["-filter_complex", "[0:a]asetpts=N/SR/TB[s0]", "-map", "[s0]",
-                        "-c:a", "aac", out_m4a, "-y"])
+                        "-c:a", "aac", "-b:a", self.bitrate, out_m4a, "-y"])
             tasks.append({
                 "name": file.stem,
                 "command": cmd

src/m4b_util/subcommands/bind.py

@@ -16,6 +16,7 @@ def _parse_args():
     )
     parser.add_argument('input_folder', nargs="?", type=str, help="The folder to scan for input files.")
     parser.add_argument('-a', "--author", type=str, help="Name of the author.")
+    parser.add_argument('-b', "--bitrate", type=str, default="128k", help="Bitrate to use for the audiobook. (e.g. 128k)")
     parser.add_argument('-c', "--cover", type=str, help="Image file to use as cover")
     parser.add_argument('-f', "--files", nargs='+', type=str, action='extend',
                         help="Specific files to use for the audiobook. Overrides `input_folder`.")
@@ -40,7 +41,7 @@ def check_args(input_folder, files, output_dir):
     # We either need an input folder or a list of files.
     if not input_folder and not files:
         print("[bold red]Error:[/] You must provide either an input folder or a list of files.")
-        return -1
+        return False
 
     # Warn the user if they specified both an input folder and a list of files.
     if input_folder and files:
@@ -50,18 +51,22 @@ def check_args(input_folder, files, output_dir):
     # Make sure the output directory exists, if it was specified.
     if output_dir and not Path(output_dir).is_dir():
         print(f"[bold red]Error:[/] '{output_dir}' is not a directory.")
-        return -1
+        return False
+
+    return True
 
 
 def run():
     """Entrypoint for bind subcommand."""
     args = _parse_args()
 
-    check_args(args.input_folder, args.files, args.output_dir)
+    if not check_args(args.input_folder, args.files, args.output_dir):
+        return -1
 
     # Set info from args
     book = Audiobook(
         author=args.author,
+        bitrate=args.bitrate,
         cover=args.cover,
         output_name=args.output_name,
         title=args.title,
@@ -95,9 +100,6 @@ def run():
             return 0
 
         # Add the files to the binder
-        if not args.input_folder:
-            print("[red]Error:[/] No input folder specified.")
-            return -1
         book.add_chapters_from_directory(
             input_dir=args.input_folder,
             use_filenames=args.use_filename,

src/m4b_util/subcommands/slide.py

@@ -13,6 +13,7 @@ def _parse_args():
         description='Slide chapter segments up or down.'
     )
     parser.add_argument('input_file', help='Input filename')
+    parser.add_argument('-b', "--bitrate", type=str, default="128k", help='Bitrate to use for the audiobook. (e.g. 128k)')
     parser.add_argument('-d', "--duration", type=float, help='Duration to shift (seconds). Negative values allowed.')
     parser.add_argument("--trim-start", type=float, help='Duration to trim from beginning (seconds).')
 
@@ -99,7 +100,7 @@ def run():
     if args.trim_start:
         slide_dur = slide_dur - args.trim_start
 
-    book = Audiobook()
+    book = Audiobook(bitrate=args.bitrate)
     book.add_chapters_from_chaptered_file(input_path)
     if book.chapters:
         # Find initial end times, in case we need to modify it.

tests/conftest.py

@@ -35,11 +35,13 @@ def test_data_path():
     # Since __file__ returns the file name, we need to call parent to get the directory
     return Path(__file__).parent.joinpath("data").absolute()
 
+
 @pytest.fixture(scope='session')
 def cover_image_path(test_data_path):
     """Path to the cover image used in tests."""
     return test_data_path / f"cover_{platform.system().lower()}.png"
 
+
 @pytest.fixture()
 def wav_path(tmp_path):
     """Path to a temporary folder with a number of short wav files."""

tests/helpers/test_audiobook.py

@@ -638,3 +638,18 @@ def test_set_metadata():
     assert b.chapters[1].title == "Part I"
     assert b.chapters[1].start_time == 330.987
     assert b.chapters[1].end_time == 335.943
+
+
+def test_custom_bitrate(mp3_path, tmp_path):
+    """Bind an audiobook with a custom bitrate."""
+    out_file_path = tmp_path / "Book.m4b"
+    b = Audiobook(bitrate="64k")
+    b.add_chapters_from_directory(mp3_path)
+    b.bind(out_file_path)
+
+    # Verify output
+    probe = ffprobe.run_probe(out_file_path)
+    assert probe
+
+    # Check bitrate
+    assert probe.format['bit_rate'] == "35380"

tests/subcommands/test_cover.py

@@ -1,6 +1,5 @@
 """Cover Subcommand Tests."""
 import filecmp
-import platform
 import shutil
 from unittest import mock