Convert HEVC to M4B — Free Online Tool
Convert HEVC/H.265 video files to M4B audiobook format by extracting and encoding the audio track to AAC at 128k bitrate. Ideal for turning recorded lectures, video courses, or narrated content into a bookmarkable, chapter-ready audiobook file playable in Apple Books, Overcast, and other podcast apps.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your HEVC file here
or click to browse
Free — no uploads, no signups. Your files never leave your browser.
Settings
Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
HEVC (H.265) is a video container that typically carries both a video stream and one or more audio streams. Since M4B is a pure audio format — essentially an MPEG-4 container with an audiobook-specific extension — the video stream is completely discarded during this conversion. The audio track from the HEVC source is transcoded (re-encoded) into AAC at 128k bitrate, which is the standard codec for M4B files. The output is then wrapped with the +faststart flag, which moves the MPEG-4 metadata to the beginning of the file, enabling progressive playback and streaming from apps like Apple Books without waiting for the full file to download.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg program, the open-source multimedia processing engine that handles the audio extraction, transcoding, and container packaging for this HEVC-to-M4B conversion. |
-i input.hevc
|
Specifies the input file — an HEVC/H.265 encoded source, which may contain both a video stream and one or more audio streams that FFmpeg will analyze before processing. |
-c:a aac
|
Sets the audio codec to AAC (Advanced Audio Coding), which is the required codec for M4B files and the native audio format of Apple's audiobook and podcast ecosystem. |
-b:a 128k
|
Sets the AAC audio bitrate to 128 kilobits per second, which is the default quality level — well-suited for spoken-word audiobook content and universally compatible with M4B-capable players. |
-movflags +faststart
|
Moves the MPEG-4 metadata (moov atom) to the beginning of the output file, enabling Apple Books, Overcast, and other audiobook apps to begin playback immediately when streaming rather than waiting for the entire M4B to download. |
output.m4b
|
Defines the output filename with the .m4b extension, which signals to media players that this MPEG-4 audio file should be treated as an audiobook — enabling bookmarking, chapter navigation, and variable playback speed controls. |
Common Use Cases
- Convert a recorded university lecture saved as an H.265 video into an M4B audiobook so you can listen on your commute with your place automatically bookmarked
- Turn a downloaded video course in HEVC format into an M4B file for distraction-free audio-only study sessions in Apple Books or Pocket Casts
- Extract narrated audio from an H.265 screen recording tutorial and package it as an M4B podcast episode for distribution
- Convert an HEVC-encoded documentary or narrated film into an M4B so visually impaired listeners can consume the audio with audiobook playback controls
- Strip the audio from a 4K HEVC home video of a family story or memoir reading and archive it as a lightweight, bookmarkable M4B audiobook
- Prepare a narrated slide presentation exported as HEVC video into an M4B for colleagues who want to review it as an audio briefing during travel
Frequently Asked Questions
No — M4B is a strictly audio format and cannot store video streams. During this conversion, the H.265 video track is completely dropped, and only the audio track is extracted and re-encoded to AAC. If preserving the video is important, consider converting to MP4 or MKV instead.
Yes, there is some quality loss because the audio is transcoded to AAC at 128k bitrate, which is a lossy compression format. However, for spoken-word content like lectures or audiobooks, 128k AAC is widely considered more than sufficient — the loss is practically inaudible for voice. If the source HEVC file has high-quality music or lossless audio, you may want to increase the bitrate to 192k or 256k using the FFmpeg command.
The M4B container format natively supports chapters and bookmarking, and apps like Apple Books and Overcast will resume playback from where you left off. However, this conversion tool extracts and re-encodes the audio track only — chapter markers are not automatically generated from the HEVC source. To add chapters, you would need to inject chapter metadata into the M4B using a tool like mp4chaps after conversion.
Replace the '-b:a 128k' flag value with a higher bitrate such as 192k, 256k, or 320k. For example: 'ffmpeg -i input.hevc -c:a aac -b:a 256k -movflags +faststart output.m4b'. Higher bitrates produce larger files but better audio fidelity, which matters most for music-heavy content. For voice-only audiobooks, 128k is typically indistinguishable from higher settings.
Yes. On macOS or Linux, you can loop over files with a shell command like: 'for f in *.hevc; do ffmpeg -i "$f" -c:a aac -b:a 128k -movflags +faststart "${f%.hevc}.m4b"; done'. On Windows, a similar for-loop works in PowerShell. This is especially useful when converting a full video course with many HEVC episode files into individual M4B chapters.
Some HEVC files, particularly raw bitstream files with the .hevc extension, may not contain an embedded audio track — they store only the compressed video stream. If the conversion produces a silent or empty M4B, your source file likely has no audio. Try inspecting the file with 'ffprobe input.hevc' in your terminal to confirm whether an audio stream is present before converting.
Technical Notes
M4B files use the MPEG-4 Part 14 container — essentially the same structure as MP4 — but with an audiobook-specific MIME type and iTunes metadata extensions that signal to media players to treat the file as an audiobook rather than music or a podcast. The AAC encoder used here is FFmpeg's native AAC implementation, which produces solid quality at 128k and is universally compatible with Apple devices, Android, and all major podcast apps. One notable limitation of this conversion is that HEVC files may contain multiple audio tracks (e.g., multiple languages), but M4B supports only a single audio track — FFmpeg will select the default or first audio track automatically. Additionally, any embedded subtitles, HDR metadata, or chapter data embedded in the HEVC container are not transferred, as M4B does not support subtitles and chapters must be explicitly authored. The -movflags +faststart flag reorders the MPEG-4 moov atom to the front of the file, which is important for streaming playback in apps that begin buffering before the full file is downloaded. For very long recordings (several hours), consider splitting the output into multiple M4B files to improve navigation within audiobook apps.