M4B Audiobook Chapters

Read a book's actual chapters, audition the cut points, then export to a new folder. The original M4B / M4A stays read-only. If it has no embedded chapters, explicitly choose fixed-length splitting to generate segments; you can then edit their start/end times. The app does not detect chapters from silence or plot.

The app interface is in Chinese; on-screen labels are quoted so you can follow along.

Before you start

• You are signed in (Admin & NAS Sign-in).
• The audiobook folder has been granted as an input folder (read permission), and an output location has been granted (read and write permission).
• Input can be M4B, M4A, or other audio files (MP3, FLAC, WAV, APE, OGG, OPUS, AAC, AIFF).

The result to aim for

This example data uses a short audio file to show the whole process. Your book lists its real chapters; you do not need to rename it to match the example:

Input	Book title	Chapters read
Generated-Chapters.m4b, 12 seconds of AAC audio	生成的章节集	第一章 00:00–00:04, 第二章 00:04–00:08, 第三章 00:08–00:12

Keep all three chapters and choose M4A to produce three separate files. If you have a CUE plus whole-track audio instead, use Album CUE Splitting; the audiobook tool does not list CUE files.

Full workflow: split by embedded chapters

1. In the left sidebar under 音频工具 (Audio Tools), choose 有声书切章 (Audiobook Chapters).
2. Click 输入文件 → 浏览 (Input file → Browse), enter a granted folder and pick the M4B / M4A file. The app starts 读取音频 (Read audio) immediately. Progress counts source files, usually one for a single audiobook; click 停止 (Stop) to cancel this step. It analyzes and stages a copy, without exporting split files yet.
3. When reading finishes, check the chapter list (next section).
4. Click 输出目录 → 浏览 (Output folder → Browse) and choose a save location.
5. Under 输出格式 (Output format) at the bottom, pick a format (default M4A · AAC; for AAC input you can tick 原音质直切 (Original-quality direct copy)).
6. Click 预览并切割 (Preview & Split).
7. In the 输出预览 (Output Preview) dialog, check each file's name, start, end, and duration, tick 确认输出 N 个文件 (Confirm exporting N files), then click 开始切割 (Start Splitting).
8. When done, the result screen shows N 个文件已输出 (N files written) and the output path. Click 打开输出目录 (Open output folder) (fnOS entry) to look inside, or check per-file results in Processing History.

Interface example: book titles, tracks, paths, and processing results are sample data.

Check the three output files

For this example, 输出预览 (Output preview) should list three chapters of four seconds each and show 确认输出 3 个文件 (Confirm 3 files). Click 开始切割 (Start splitting), wait, then check both the three-file count and each item in history. The folder layout is similar to:

Source folder/
  Generated-Chapters.m4b            ← unchanged
Output folder/
  生成的章节集_job-id/
    01 - 第一章.m4a
    02 - 第二章.m4a
    03 - 第三章.m4a

Play the beginning and end of each output and check the durations before processing a long book. A successful preview only creates a plan; confirm actual splitting with each item's 已输出 (Written) state and the real file. See output and history for stopping, partial completion and retrying.

Checking and editing chapters

After reading, the table in the center lists every chapter:

Column	Meaning
Checkbox	Only checked chapters are written; the header checkbox selects/deselects all
#	Chapter number; becomes the filename prefix
Chapter name	Editable; decides the output file name and the title tag inside the file
Start / End	Editable, format HH:MM:SS, milliseconds allowed as in 01:12:30.500
Duration	Recalculated from the current start/end
Audition	Play button, see below

Above the table you can edit 书名 (Book title) and 作者 / 演播 (Author / Narrator) — both are written into the output tags — and you can see the input codec, sample rate, and cover thumbnail. The book title is pre-filled from tags or the file name. If cleared, fill it in before opening the output preview. 查找章节 (Find chapters) at the top right filters long books by name or number; to start over with a different file, click 清空 (Clear) and pick a new input.

Searching changes visible rows without clearing selections. The header checkbox selects/deselects the whole chapter list. Check 已选择 N / 总数 章节 (N / total selected) before execution. Re-reading generates the list again and resets names, cut-point edits and selections.

Audition: click the play button or any segment on the timeline at the top to play up to 8 seconds from the currently entered start time, stopping at the segment end if sooner — a quick way to verify cut points. The audition clip is generated quickly for checking purposes and does not sound like the final output. If audition fails, re-read the audio first.

Timeline: segment widths follow real durations, and unchecked chapters are dimmed, so missing chapters are easy to spot.

Editing start and end times

• Start must be before end, every segment at least 0.02 seconds; end cannot exceed the audio's real length.
• Chapters of the same audio must not overlap or be out of order. Invalid edits are rejected when you click 预览并切割 (Preview & Split), with a specific message; fix them and click it again.

Fixed-length splitting

For audiobooks, lectures, or radio drama recordings without chapter marks, split by a fixed length:

1. Change 切割方式 (Cut mode) to 固定时长 (Fixed length).
2. Enter 每段 … 分钟 (minutes per segment; 0.5 steps supported, e.g. 10 or 25.5).
3. Click 重新读取 (Re-read). If an analysis had already succeeded, changing settings makes the button read 应用切割方式 (Apply cut settings); click it to regenerate segments. Preview & Split stays disabled until the new settings are applied.
4. The app generates the segments; checking, auditioning, and output work exactly as with embedded chapters.

Rules:

• Each segment is between 1 second and 24 hours; at most 1,000 segments per task — increase the length per segment if you exceed it.
• A final segment shorter than 0.02 seconds is merged into the previous one; no fragment files.
• Segments are named 第 001 节、第 002 节… (Section 001, 002 …) by default. The app never guesses plot or chapter names; rename segments in the table.
• Example: a 62-minute audio split into 10-minute segments yields six 10-minute files and one 2-minute file.

What if there are no embedded chapters

If 内嵌章节 (Embedded chapters) is selected but the audio has no chapter marks, the app shows 这段音频没有内嵌章节 ("this audio has no embedded chapters") and does not guess; at that point the chapter table does not exist yet, so there is nothing to type into. The working path: switch to 固定时长 (Fixed length), then click 重新读取 (Re-read), or 应用切割方式 (Apply cut settings) if a previous result exists, to generate segments, then adjust each segment's start and end in the table to the real chapter positions (use audition to verify segment by segment).

Original-quality direct copy (AAC → M4A)

When the input is AAC-encoded and the output format is M4A, a 原音质直切 (Original-quality direct copy) checkbox appears at the bottom (ticked by default):

• Ticked: the audio stream is copied without re-encoding — fast, and the quality is identical to the source. Cut points align to audio frame boundaries and may differ slightly from the values you typed; durations are still verified after output.
• Unticked: the audio is re-encoded to AAC 192 kbps; cut points are more precise but quality cannot exceed the source.

See Output formats for MP3, FLAC, and WAV.

Common failures and recovery

Message / symptom	Cause	What to do
这段音频没有内嵌章节	No chapter marks, so no editable table yet	Choose fixed length, click Re-read, then adjust start/end in the generated table
曲目起止时间越界、倒序或长度不足	Start ≥ end, length under 0.02 s, or end beyond audio length	Fix start / end in the table and preview again
章节存在重叠或乱序	Source chapters were rejected during reading; no table is generated	Use fixed length and re-read before editing, or use a source with corrected chapter metadata
音频章节超过 1,000 个	Reading already exceeds the limit; deselecting later cannot reduce it	Use fixed length with longer segments, or prepare a smaller source
源音频已发生变化，请重新读取章节	Source file changed after reading (modified by another program)	Let the source settle, then select the input again
应用数据空间不足	Not enough space for the read-only staging copy	Free up NAS space and retry
The other tool button in the sidebar is disabled	An audiobook task is running; switching tools is paused	Wait for the task, or stop it

Limits

• Total source audio per task: up to 10 GB. Reading needs app temporary space for a staged copy.
• Reading chapters and auditioning do not change sources. Output plans expire after 30 minutes; preview again when expired.
• Manual edits adjust generated segments; there is no free-form add-cut-point or silence-detection entry.
• DRM-encrypted (copy-protected) M4B / M4A is not supported.
• This tool only splits: no merging, no speech-to-text, no automatic chapter naming.